M12/4/CHEMI/HPM/ENG/TZ1/XX
22126107
CHEMISTRY
Higher level
Paper 1
Tuesday 8 May 2012 (afternoon)
1 hour
INSTRUCTIONS TO CANDIDATES
• Do not open this examination paper until instructed to do so.
• Answer all the questions.
• For each question, choose the answer you consider to be the best and indicate your choice on
the answer sheet provided.
• The periodic table is provided for reference on page 2 of this examination paper.
• The maximum mark for this examination paper is [40 marks].
2212-6107
19 pages
© International Baccalaureate Organization 2012
2212-6107
23
V
50.94
87
Fr
(223)
88
Ra
(226)
‡
†
89 ‡
Ac
(227)
90
Th
232.04
58
Ce
140.12
91
Pa
231.04
59
Pr
140.91
73
Ta
180.95
38
Sr
87.62
37
Rb
85.47
22
Ti
47.90
56
57 †
72
55
Ba
La
Cs
Hf
132.91 137.34 138.91 178.49
20
Ca
40.08
19
K
39.10
41
Nb
92.91
39
Y
88.91
12
Mg
24.31
11
Na
22.99
92
U
238.03
60
Nd
144.24
74
W
183.85
42
Mo
95.94
24
Cr
52.00
Relative atomic mass
Element
Atomic number
40
Zr
91.22
21
Sc
44.96
4
Be
9.01
2
3
Li
6.94
1
H
1.01
1
30
Zn
65.37
93
Np
(237)
94
Pu
(242)
95
Am
(243)
96
Cm
(247)
97
Bk
(247)
98
Cf
(251)
61
66
62
63
64
65
Pm
Dy
Sm
Tb
Eu
Gd
146.92 150.35 151.96 157.25 158.92 162.50
75
80
76
77
78
79
Re
Os
Pt
Au
Hg
Ir
186.21 190.21 192.22 195.09 196.97 200.59
48
44
45
46
47
Cd
Ru
Rh
Pd
Ag
101.07 102.91 106.42 107.87 112.40
29
Cu
63.55
43
Tc
98.91
28
Ni
58.71
26
Fe
55.85
25
Mn
54.94
27
Co
58.93
The Periodic Table
50
Sn
118.69
32
Ge
72.59
14
Si
28.09
6
C
12.01
4
99
Es
(254)
100
Fm
(257)
67
68
Ho
Er
164.93 167.26
81
82
Tl
Pb
204.37 207.19
49
In
114.82
31
Ga
69.72
13
Al
26.98
5
B
10.81
3
101
Md
(258)
69
Tm
168.93
83
Bi
208.98
51
Sb
121.75
33
As
74.92
15
P
30.97
7
N
14.01
5
35
Br
79.90
17
Cl
35.45
9
F
19.00
7
85
At
(210)
102
No
(259)
103
Lr
(260)
70
71
Lu
Yb
173.04 174.97
84
Po
(210)
52
53
Te
I
127.60 126.90
34
Se
78.96
16
S
32.06
8
O
16.00
6
86
Rn
(222)
54
Xe
131.30
36
Kr
83.80
18
Ar
39.95
10
Ne
20.18
2
He
4.00
0
–2–
M12/4/CHEMI/HPM/ENG/TZ1/XX
–3–
1.
2.
M12/4/CHEMI/HPM/ENG/TZ1/XX
How many atoms of hydrogen are in 0.500 mol of CH3OH molecules?
A.
1.20 ×1023
B.
3.01×1023
C.
6.02 ×1023
D.
1.20 ×1024
Calcium carbonate reacts with hydrochloric acid according to the following equation.
CaCO3 (s) + 2HCl (aq) → CaCl2 (aq) + CO 2 (g) + H 2 O (l)
What is the theoretical yield, in mol, of calcium chloride if 0.10 mol CaCO3 is added to 100 cm3 of
1.0 mol dm–3 HCl?
3.
A.
0.050
B.
0.10
C.
0.20
D.
0.50
A fixed mass of an ideal gas at 27.0 °C and 1.01×105 Pa has a volume of 100 cm3. Which change
doubles the volume of the gas?
A.
Heating the gas at constant pressure to 54.0 °C .
B.
Heating the gas at constant pressure to 327 °C .
C.
Increasing the pressure on the gas to 2.02 ×105 Pa at constant temperature.
D.
Heating the gas to 54.0 °C and increasing the pressure to 2.02 ×105 Pa.
2212-6107
Turn over
–4–
4.
5.
6.
7.
M12/4/CHEMI/HPM/ENG/TZ1/XX
Which isotope has an atomic number of 9 and a mass number of 19?
A.
9
B.
19
C.
19
D.
28
F
K
F
Si
What is the order in which the energy sub-levels are occupied according to the Aufbau principle?
A.
5s, 5p, 4d
B.
4d, 5s, 5p
C.
5s, 4d, 5p
D.
5s, 5d, 5p
Which species are in the order of increasing ionic radius?
A.
Cl– < K+ < S2–
B.
K+ < Cl– < S2–
C.
Cl– < S2– < K+
D.
S2– < Cl– < K+
Which combination of descriptions is correct for the oxides of period 3 elements?
Chlorine
Magnesium
Silicon
Sodium
A.
basic
acidic
basic
acidic
B.
acidic
basic
basic
basic
C.
basic
acidic
acidic
acidic
D.
acidic
basic
acidic
basic
2212-6107
–5–
8.
9.
M12/4/CHEMI/HPM/ENG/TZ1/XX
What are the electron configurations of Cu, Cu+ and Cu2+?
Cu
Cu+
Cu2+
A.
[Ar] 4s2 3d9
[Ar] 4s2 3d8
[Ar] 4s2 3d7
B.
[Ar] 4s2 3d9
[Ar] 4s1 3d9
[Ar] 3d9
C.
[Ar] 4s2 3d9
[Ar] 3d10
[Ar] 3d9
D.
[Ar] 4s1 3d10
[Ar] 3d10
[Ar] 3d9
What is the correct number of centres of negative charge for carbon and the shape of H2CO?
H
C
O
H
10.
Centres of negative
charge on C-atom
Shape
A.
3
trigonal pyramidal
B.
3
trigonal planar
C.
4
trigonal pyramidal
D.
4
trigonal planar
Which statement about intermolecular forces is correct?
A.
The intermolecular force between H2 molecules is hydrogen bonding, because H2 has
temporary dipoles.
B.
The intermolecular forces between PH3 molecules are greater than the intermolecular forces
between NH3 molecules, because they have a greater mass.
C.
The intermolecular force between H2 molecules is hydrogen bonding, because H2 has permanent
dipoles.
D.
The intermolecular forces between Br2 molecules are van der Waals’, because Br2 has
temporary dipoles.
2212-6107
Turn over
–6–
11.
12.
M12/4/CHEMI/HPM/ENG/TZ1/XX
Which substances are soluble in hexane, C6H14?
I.
C8H18
II.
CH4
III.
H2O
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
Diagrams I and II show two p orbitals on adjacent atoms in different relative orientations.
I
II
Which types of bonds are formed when the orbitals overlap?
Orientation I
Orientation II
A.
σ
σ
B.
π
π
C.
π
σ
D.
σ
π
2212-6107
–7–
13.
14.
M12/4/CHEMI/HPM/ENG/TZ1/XX
Which molecules have delocalized π electrons?
I.
C6H6
II.
CH3COOH
III.
O3
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
What are the units for specific heat capacity?
A.
kJ kg K
B.
kJ kg K–1
C.
kJ kg–1 K
D.
kJ kg–1 K–1
2212-6107
Turn over
–8–
15.
M12/4/CHEMI/HPM/ENG/TZ1/XX
In each of two different experiments, A and B, a solution of sodium hydroxide is added to a solution
of hydrochloric acid. The initial temperature of each solution is 25 °C .
50 cm3
1.0 mol dm–3 NaOH (aq)
50 cm3
1.0 mol dm–3 NaOH (aq)
50 cm3
1.0 mol dm–3 HCl (aq)
100 cm3
1.0 mol dm–3 HCl (aq)
Experiment A
Experiment B
Which statement is correct?
A.
The highest recorded temperature of experiment A is lower than the highest recorded temperature
of experiment B.
B.
The highest recorded temperature of both experiments is equal.
C.
The heat produced in experiment A is lower than the heat produced in experiment B.
D.
The heat produced in both experiments is equal.
2212-6107
–9–
16.
M12/4/CHEMI/HPM/ENG/TZ1/XX
The diagram represents the Born–Haber cycle for the lattice enthalpy of sodium chloride.
Na (g) + Cl (g)
I
II
Na (g) + 12 Cl2 (g)
H
Na (s) + 12 Cl2 (g)
III
NaCl (s)
What is the name of the enthalpy changes I, II and III?
I
17.
II
III
A.
ionization energy of Na
electron affinity of Cl
lattice enthalpy of NaCl
B.
lattice enthalpy of NaCl
ionization energy of Na
electron affinity of Cl
C.
electron affinity of Cl
ionization energy of Na
lattice enthalpy of NaCl
D.
ionization energy of Na
lattice enthalpy of NaCl
electron affinity of Cl
Which statements about entropy for the following reaction at 298 K are correct?
2NO (g) + O 2 (g) → 2NO 2 (g)
I.
S Ö (O 2 ) = 0
II.
ëS Ö = 2 S Ö (NO 2 ) − 2 S Ö (NO) − S Ö (O 2 )
III.
ëS Ö < 0
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
2212-6107
Turn over
– 10 –
18.
19.
M12/4/CHEMI/HPM/ENG/TZ1/XX
Which reaction is spontaneous at high temperatures, but not at low temperatures?
A.
CH 4 (g) + 2O 2 (g) → CO 2 (g) + 2H 2 O (g)
ëH < 0
B.
CaCO3 (s) → CO 2 (g) + CaO (s)
ëH > 0
C.
Fe (s) + Cl2 (g) → FeCl2 (s)
ëH < 0
D.
2C (s) + 2H 2 O (g) → CH 3COOH (l)
ëH > 0
The Maxwell–Boltzmann curve below shows the distribution of kinetic energies for the particles in a
sample of gas.
Number of
particles
Kinetic Energy
Which is the shape of the curve for the same sample of gas at a higher temperature? All graphs are
drawn to the same scale.
A. Number of
particles
B. Number of
particles
Kinetic Energy
C. Number of
particles
D. Number of
particles
Kinetic Energy
2212-6107
Kinetic Energy
Kinetic Energy
– 11 –
20.
M12/4/CHEMI/HPM/ENG/TZ1/XX
The decomposition of N2O5 occurs according to the following equation.
2N 2 O5 (g) → 4NO 2 (g) + O 2 (g)
The reaction is first order with respect to N2O5. What combination of variables could the axes represent
on the graph below?
y
x
x-axis
21.
y-axis
A.
time
[N2O5]
B.
[N2O5]
time
C.
[N2O5]
rate of reaction
D.
rate of reaction
[N2O5]
What is the effect of an increase in temperature on the rate constant of the forward reaction, k, and on
the equilibrium constant, Kc, of an exothermic reversible reaction?
A.
k decreases, Kc increases
B.
k increases, Kc decreases
C.
k decreases, Kc decreases
D.
k increases, Kc increases
2212-6107
Turn over
– 12 –
22.
M12/4/CHEMI/HPM/ENG/TZ1/XX
The graph represents the rates of the forward and backward reactions of a reversible reaction. Rate of reaction
X
W
Y
Z
Time
Which statement is correct?
23.
A.
XWZ represents the rate of the forward reaction.
B.
At Y, the rate of the forward and backward reactions is zero.
C.
Between W and Z, the concentrations of products and reactants are equal.
D.
Between Y and W, the concentration of the reactants increases.
A liquid and its vapour are at equilibrium in a sealed container. Which of the following increase as
the container is heated?
I.
The mass of the liquid.
II.
The vapour pressure of the liquid.
III.
The rate of vaporization of the liquid.
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
2212-6107
– 13 –
24.
25.
M12/4/CHEMI/HPM/ENG/TZ1/XX
Which are conjugate acid/base pairs according to the Brønsted–Lowry theory?
I.
NH4+/NH3
II.
HCOOH/HCOO–
III.
H2SO4/SO42–
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
An aqueous solution X reacts with a solid Y, to produce a flammable gas. Which of the following
suggestions could substances X and Y be?
X
26.
Y
A.
nitric acid, HNO3
calcium carbonate, CaCO3
B.
sulfuric acid, H2SO4
zinc, Zn
C.
hydrochloric acid, HCl
copper, Cu
D.
sodium hydroxide solution, NaOH
aluminum oxide, Al2O3
Which is correct for a weak acid, HA, with concentration 0.01 mol dm–3 at 298K?
A.
[H+] < 1×10 –2
B.
pH < 2
C.
[OH–] < 1×10 –12
D.
pOH >12
2212-6107
Turn over
– 14 –
27.
28.
M12/4/CHEMI/HPM/ENG/TZ1/XX
Which salt has the lowest pH when dissolved in water?
A.
KNO3
B.
CH3COONa
C.
Na2CO3
D.
[Fe(H2O)6]Cl3
Which of the following mixtures would result in the pKa of the acid being obtained from a direct pH
measurement of the resulting solution?
A.
25 cm3 0.1 mol dm–3 HCl and 25 cm3 0.1 mol dm–3 NaCl
B.
25 cm3 0.1 mol dm–3 NaOH and 25 cm3 0.1 mol dm–3 CH3COOH
C.
12.5 cm3 0.1 mol dm–3 CH3COOH and 25 cm3 0.1 mol dm–3 NaOH
D.
12.5 cm3 0.1 mol dm–3 NaOH and 25 cm3 0.1 mol dm–3 CH3COOH
2212-6107
– 15 –
29.
M12/4/CHEMI/HPM/ENG/TZ1/XX
An aqueous solution of a weak acid containing an indicator is titrated with a strong base, resulting in
the following titration curve.
14
12
10
pH
8
6
4
2
0
Volume of base
At which pH does the buffer region occur?
30.
A.
Between 4.5 and 5.5
B.
Between 7.5 and 9.5
C.
At 9.5
D.
At 12
The equation for the redox reaction between acidified dichromate and iodide ions is shown below.
Cr2 O7 2– (aq) + 6I – (aq) + 14H + (aq) → 2Cr 3+ (aq) + 3I 2 (aq) + 7H 2 O (l)
Which is the reduction half-equation?
A.
6I – (aq) + 6e − → 3I 2 (aq)
B.
6I – (aq) → 3I 2 (aq) + 6e −
C.
Cr2 O7 2– (aq) + 14H + (aq) + 6e − → 2Cr 3+ (aq) + 7H 2 O (l)
D.
Cr2 O7 2– (aq) + 14H + (aq) → 2Cr 3+ (aq) + 7H 2 O (l) + 6e −
2212-6107
Turn over
– 16 –
31.
M12/4/CHEMI/HPM/ENG/TZ1/XX
The equation for the overall reaction in a voltaic cell is:
Cu 2+ (aq) + Zn (s) → Cu (s) + Zn 2+ (aq)
Which statements are correct for this cell?
32.
I.
Cu is the positive electrode.
II.
Negative ions flow from the zinc solution to the copper solution.
III.
Chemical energy is converted into electrical energy during this reaction.
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
Which statement is correct for the following spontaneous reaction?
2Fe3+ (aq) + 2Br – (aq) → 2Fe 2+ (aq) + Br2 (aq)
33.
A.
ëE Ö < 0 and Br2 is a better oxidizing agent than Fe3+.
B.
ëE Ö < 0 and Br– is a better reducing agent than Fe2+.
C.
ëE Ö > 0 and Fe3+ is a better oxidizing agent than Br2.
D.
ëE Ö > 0 and Fe2+ is a better reducing agent than Br–.
Which combination of electrodes and electrolyte could be used to plate a spoon with silver?
Negative electrode
(cathode)
Positive electrode
(anode)
Electrolyte
A.
silver
spoon
sulfuric acid solution
B.
spoon
silver
sulfuric acid solution
C.
silver
spoon
silver nitrate solution
D.
spoon
silver
silver nitrate solution
2212-6107
– 17 –
34.
35.
36.
M12/4/CHEMI/HPM/ENG/TZ1/XX
Which statements about CH3CH2CHO are correct?
I.
It can be oxidized to CH3CH2COOH.
II.
It can be produced by oxidation of CH3CH2OH.
III.
It can be reduced to CH3CH2CH2OH.
A.
I and II only
B.
I and III only
C.
II and III only D.
I, II and III
Which reaction of but-2-ene produces 2-chlorobutane?
A.
Addition reaction with chlorine
B.
Substitution reaction with hydrogen chloride
C.
Substitution reaction with chlorine
D.
Addition reaction with hydrogen chloride
What are the correct names of the reaction types shown?
I → ClCH CH CH 
II → HOCH CH CH
CH 3CH 2 CH 3 
2
2
3
2
2
3
I
II
A.
nucleophilic substitution
oxidation
B.
free-radical substitution
oxidation
C.
nucleophilic substitution
nucleophilic substitution
D.
free-radical substitution
nucleophilic substitution
2212-6107
Turn over
– 18 –
37.
What is the name of the substance below?
H
38.
39.
M12/4/CHEMI/HPM/ENG/TZ1/XX
A.
Pentanenitrile
B.
2-methyl-2-propanenitrile
C.
2,2-dimethylpropanenitrile
D.
1,1-dimethylethanenitrile
H
CH3
C
C
H
CH3
CN
What is the correct order of increasing rate of reaction between the following halogenoalkanes and a
warm aqueous solution of sodium hydroxide?
A.
CH3F < CH3Cl < (CH3)2CHCl
B.
CH3Cl < CH3F < (CH3)2CHCl
C.
CH3Cl < (CH3)2CHCl < CH3F
D.
(CH3)2CHCl < CH3Cl < CH3F
Which statements are correct for the nylon shown below?
[ OC(CH 2 ) 4 CONH(CH 2 )6 NH ] n
I.
It is produced by condensation polymerization.
II.
It is a polyamide.
III.
One of its monomers is H2N(CH2)6NH2.
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
2212-6107
– 19 –
40.
M12/4/CHEMI/HPM/ENG/TZ1/XX
A student measured the mass of a solid on an analytical balance during an internally assessed IB
practical experiment and recorded the mass in his raw data. The accuracy of the balance, as stated
by the manufacturers, was ± 0.01 g. Which of the following choices would be the best record of
his mass?
A.
10.2 g
B.
10 g
C.
10.20 g
D.
10.200 g
2212-6107
M12/4/CHEMI/HPM/ENG/TZ1/XX/M
MARKSCHEME
May 2012
CHEMISTRY
Higher Level
Paper 1
2 pages
–2–
M12/4/CHEMI/HPM/ENG/TZ1/XX/M
1.
D
16.
A
31.
B
46.
–
2.
A
17.
C
32.
C
47.
–
3.
B
18.
B
33.
D
48.
–
4.
C
19.
A
34.
B
49.
–
5.
C
20.
A
35.
D
50.
–
6.
B
21.
B
36.
D
51.
–
7.
D
22.
A
37.
C
52.
–
8.
D
23.
C
38.
A
53.
–
9.
B
24.
A
39.
D
54.
–
10.
D
25.
B
40.
C
55.
–
11.
A
26.
A
41.
–
56.
–
12.
C
27.
D
42.
–
57.
–
13.
B
28.
D
43.
–
58.
–
14.
D
29.
A
44.
–
59.
–
15.
D
30.
C
45.
–
60.
–
M12/4/CHEMI/HPM/ENG/TZ2/XX
22126113
CHEMISTRY
HIGHER LEVEL
PAPER 1
Tuesday 8 May 2012 (afternoon)
1 hour
INSTRUCTIONS TO CANDIDATES
• Do not open this examination paper until instructed to do so.
• Answer all the questions.
• For each question, choose the answer you consider to be the best and indicate your choice on
the answer sheet provided.
• The periodic table is provided for reference on page 2 of this examination paper.
• The maximum mark for this examination paper is [40 marks].
2212-6113
19 pages
© International Baccalaureate Organization 2012
2212-6113
23
V
50.94
87
Fr
(223)
88
Ra
(226)
‡
†
89 ‡
Ac
(227)
90
Th
232.04
58
Ce
140.12
91
Pa
231.04
59
Pr
140.91
73
Ta
180.95
38
Sr
87.62
37
Rb
85.47
22
Ti
47.90
56
57 †
72
55
Ba
La
Cs
Hf
132.91 137.34 138.91 178.49
20
Ca
40.08
19
K
39.10
41
Nb
92.91
39
Y
88.91
12
Mg
24.31
11
Na
22.99
92
U
238.03
60
Nd
144.24
74
W
183.85
42
Mo
95.94
24
Cr
52.00
Relative atomic mass
Element
Atomic number
40
Zr
91.22
21
Sc
44.96
4
Be
9.01
2
3
Li
6.94
1
H
1.01
1
30
Zn
65.37
93
Np
(237)
94
Pu
(242)
95
Am
(243)
96
Cm
(247)
97
Bk
(247)
98
Cf
(251)
61
66
62
63
64
65
Pm
Dy
Sm
Tb
Eu
Gd
146.92 150.35 151.96 157.25 158.92 162.50
75
80
76
77
78
79
Re
Os
Pt
Au
Hg
Ir
186.21 190.21 192.22 195.09 196.97 200.59
48
44
45
46
47
Cd
Ru
Rh
Pd
Ag
101.07 102.91 106.42 107.87 112.40
29
Cu
63.55
43
Tc
98.91
28
Ni
58.71
26
Fe
55.85
25
Mn
54.94
27
Co
58.93
The Periodic Table
50
Sn
118.69
32
Ge
72.59
14
Si
28.09
6
C
12.01
4
99
Es
(254)
100
Fm
(257)
67
68
Ho
Er
164.93 167.26
81
82
Tl
Pb
204.37 207.19
49
In
114.82
31
Ga
69.72
13
Al
26.98
5
B
10.81
3
101
Md
(258)
69
Tm
168.93
83
Bi
208.98
51
Sb
121.75
33
As
74.92
15
P
30.97
7
N
14.01
5
35
Br
79.90
17
Cl
35.45
9
F
19.00
7
85
At
(210)
102
No
(259)
103
Lr
(260)
70
71
Lu
Yb
173.04 174.97
84
Po
(210)
52
53
Te
I
127.60 126.90
34
Se
78.96
16
S
32.06
8
O
16.00
6
86
Rn
(222)
54
Xe
131.30
36
Kr
83.80
18
Ar
39.95
10
Ne
20.18
2
He
4.00
0
–2–
M12/4/CHEMI/HPM/ENG/TZ2/XX
–3–
1.
2.
M12/4/CHEMI/HPM/ENG/TZ2/XX
What is the total number of atoms in 0.100 mol of [Pt ( NH 3 ) 2 Cl2 ]?
A.
11
B.
6.02 ×1022
C.
3.01×1023
D.
6.62 ×1023
Nitroglycerine, C3 H 5 N 3O9 , can be used in the manufacture of explosives. What is the coefficient
of C3 H 5 N 3O9 (l) when the equation for its decomposition reaction is balanced using the lowest
whole numbers?
___ C3 H 5 N 3O9 (l) → ___ CO 2 (g) + ___ H 2 O (l) + ___ N 2 (g ) + ___ O 2 (g )
3.
A.
2
B.
4
C.
20
D.
33
The volume occupied by one mole of an ideal gas at 273 K and 1.01×105 Pa is 22.4 dm3. What volume, in dm3, is occupied by 3.20 g O2 (g) at 273 K and 1.01×105 Pa?
A.
2.24
B.
4.48
C.
22.4
D.
71.7
2212-6113
Turn over
–4–
4.
5.
6.
M12/4/CHEMI/HPM/ENG/TZ2/XX
What volume, in m3, is occupied by 2.00 mol of gas at 27 °C and 2.00 atm pressure? Assume: 1.00 atm = 1.01× 105 Pa and R = 8.31 J K −1 mol−1.
A.
8.31× 27
1.01×105
B.
2.00 × 8.31× 27
1.01×105
C.
2.00 × 8.31× 300
2.00 ×1.01×105
D.
2.00 × 8.31× 300
1.01×105
In the electromagnetic spectrum, which will have the shortest wavelength and the greatest energy?
Shortest wavelength
Greatest energy
A.
ultraviolet
ultraviolet
B.
infrared
infrared
C.
ultraviolet
infrared
D.
infrared
ultraviolet
What is the electron configuration of Sn2+?
A.
1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d10 4p 6 5s 2 4d10 5p 2
B.
1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d10 4p 6 5s 2 4d10
C.
1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d10 4p 6 4d10 5p 2
D.
1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d10 4p 6 5s 2 4d8 5p 2
2212-6113
–5–
7.
8.
9.
M12/4/CHEMI/HPM/ENG/TZ2/XX
Which series is correctly arranged in order of decreasing radius?
A.
Al3+ > Mg 2+ > Na + > F−
B.
F− > Na + > Mg 2+ > Al3+
C.
F− > Al3+ > Mg 2+ > Na +
D.
Na + > Mg 2+ > Al3+ > F−
Which complex is colourless in solution?
A.
[Fe(H 2 O)6 ]Cl2
B.
[ Ni( NH 3 )6 ]Cl2
C.
[ Zn (H 2 O)6 ]( NO3 ) 2
D.
K 3 [Co(CN)6 ]
Which species contain dative covalent bonds?
I.
CO
II.
NH3
III.
H3O+
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
2212-6113
Turn over
–6–
10.
11.
M12/4/CHEMI/HPM/ENG/TZ2/XX
Which single covalent bond is the most polar, given the following electronegativity values?
A.
C–O
B.
S–H
C.
C–H
D.
O–H
Element
H
C
S
O
Electronegativity
2.2
2.6
2.6
3.4
The Lewis (electron dot) structure of paracetamol (acetaminophen) is:
O
H
H
C
C
H
C
C
H
α
C
θ
A.
104.5
120
109.5
B.
109.5
109.5
109.5
C.
120
120
90
D.
104.5
120
90
2212-6113
H H
N
C
H
What are the approximate values of the bond angles?
β
β
C
O
α
H
θ
H
–7–
12.
13.
M12/4/CHEMI/HPM/ENG/TZ2/XX
Which types of intermolecular forces exist in HBr, Cl2 and CH3F?
HBr
Cl2
CH3F
A.
van der Waals’ and
dipole-dipole
van der Waals’ only
van der Waals’ and
dipole-dipole
B.
van der Waals’ and
dipole-dipole
van der Waals’ only
van der Waals’, dipole-dipole
and hydrogen bonding
C.
van der Waals’ only
van der Waals’ only
van der Waals’, dipole-dipole
and hydrogen bonding
D.
van der Waals’ and
dipole-dipole
van der Waals’ and
dipole-dipole
van der Waals’, dipole-dipole
and hydrogen bonding
Retinol (vitamin A) contains a total of 5 double bonds and 46 single bonds.
H
H
H
C
C
H
CH3
H
CH3
H
CH3
C
C
C
C
C
C
C
C
H
H
CH3
CH3
C
H
C
H
C
H
H
C
H
H
C
O
H
Which statements are correct?
I.
There are 51 σ and 5 π bonds.
II.
The oxygen atom is sp3 hybridized.
III.
Retinol is a primary alcohol.
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
2212-6113
Turn over
–8–
14.
15.
M12/4/CHEMI/HPM/ENG/TZ2/XX
Zinc metal contains metallic bonding. Which is the best description of a metallic bond?
A.
The electrostatic attraction between a pair of electrons and positively charged nuclei.
B.
The electrostatic attraction between oppositely charged ions.
C.
The electrostatic attraction between a lattice of positive ions and delocalized electrons.
D.
The bond formed when one atom provides both electrons in a shared pair.
Which reactions are exothermic?
I.
CH 4 (g ) + 2O 2 (g ) → CO 2 (g ) + 2H 2 O (l)
II.
Reaction of aspirin with sodium hydroxide
O
H
H
C
C
H
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
2212-6113
O
C
C
O
H
C
H
Aspirin
2 H 2 (g ) + O 2 (g ) → 2 H 2 O (g )
A.
O
C
C
H
III.
C
C
H
H
–9–
16.
17.
18.
M12/4/CHEMI/HPM/ENG/TZ2/XX
Which equation represents the electron affinity of chlorine?
A.
Cl (g ) + e − → Cl− (g )
B.
Cl (g ) + e − → Cli (g )
C.
Cl2 (g ) + 2e − → 2Cl− (g )
D.
Cl (g ) → Cl+ (g ) + e −
During which process is there a decrease in the entropy of the system?
A.
Ag (s) + 2 H + (aq ) + NO3− (aq ) → Ag + (aq ) + H 2O (l) + NO 2 ( g)
B.
Ba (OH ) 2 (s) → BaO (s) + H 2O ( g)
C.
PCl3 (g ) + Cl2 (g ) → PCl5 (g )
D.
H 2 O (s) → H 2 O (l)
Which are appropriate units for the rate of a reaction?
A.
mol dm–3 s–1
B.
mol dm–3 s
C.
mol dm–3
D.
s
2212-6113
Turn over
– 10 –
19.
M12/4/CHEMI/HPM/ENG/TZ2/XX
Which graph represents a reaction that is second order with respect to X for the reaction
X → products?
A.
B.
[X]
[X]
Time
C.
D.
Rate
[X]
2212-6113
Time
[X]
Time
– 11 –
20.
M12/4/CHEMI/HPM/ENG/TZ2/XX
Consider the reaction:
2 NO (g ) + Br2 (g ) → 2 NOBr (g )
One suggested mechanism is:
k
1
NO (g ) + Br2 (g ) NOBr2 (g )
fast
k
2
NOBr2 (g ) + NO (g ) 
→ 2 NOBr (g )
slow
Which statements are correct?
21.
I.
NOBr2 (g) is an intermediate.
II.
The second step is the rate-determining step.
III.
rate = k [ NO]2 [Br2 ]
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
What happens to the position of equilibrium and the value of Kc when the temperature is increased in
the following reaction?
PCl5 (g )  PCl3 (g ) + Cl2 (g )
∆H Ö = +87.9 kJ mol−1
Position of equilibrium
Value of Kc
A.
shifts towards reactants
decreases
B.
shifts towards reactants
increases
C.
shifts towards products
decreases
D.
shifts towards products
increases
2212-6113
Turn over
– 12 –
22.
23.
24.
M12/4/CHEMI/HPM/ENG/TZ2/XX
Which statement is correct about the relationship between the vapour pressure, P, of ethanol and
temperature, T ?
A.
P increases linearly with increasing T.
B.
P decreases linearly with increasing T.
C.
P increases exponentially with increasing T.
D.
P decreases exponentially with increasing T.
Which reaction represents an acid–base reaction according to the Lewis theory but not according to
the Brønsted–Lowry theory?
A.
CO32− (aq ) + H 3O + (aq )  H 2 O (l) + HCO3− (aq )
B.
CH 3COOH (aq ) + NH 3 (aq )  NH 4 + (aq ) + CH 3COO − (aq)
C.
NH 3 (aq ) + HF (aq )  NH 4 + (aq ) + F− (aq )
D.
CuSO4 (s) + 5H 2 O (l) CuSO4 i5H 2 O (s)
Four aqueous solutions are listed below.
W.
0.100 mol dm–3 HNO3 (aq)
X.
0.001 mol dm–3 HNO3 (aq)
Y.
0.100 mol dm–3 KOH (aq)
Z.
0.001 mol dm–3 KOH (aq)
What is the correct order of increasing pH of these solutions?
A.
W<X<Y<Z
B.
W<X<Z<Y
C.
X<W<Y<Z
D.
X<W<Z<Y
2212-6113
– 13 –
25.
M12/4/CHEMI/HPM/ENG/TZ2/XX
Penicillin G (benzyl penicillin) contains a number of different functional groups and has the
following structure:
H
O
C
C
C
O
C
S
O
H
C
C
H
C
N
O
C
H
H
C
N
H
H
H
H
H
H
C
H
C
H
H
H
C
C
C
C
H
H
C
H
It is a weak monoprotic acid (pK a = 2.79 at 298 K ). At 298 K, the ionic product constant for water,
K w = 1.00 ×10−14. What is the value of pKb for the conjugate base of penicillin G and which functional
groups are present in penicillin G?
pKb
Selected functional groups in penicillin G
A.
11.21
carboxylic acid, amine
B.
2.79
carboxylic acid, amide
C.
11.21
ketone, alcohol
D.
11.21
carboxylic acid, benzene ring
2212-6113
Turn over
– 14 –
26.
27.
M12/4/CHEMI/HPM/ENG/TZ2/XX
Which mixtures are buffer solutions?
I.
KHSO4 (aq) and H2SO4 (aq)
II.
CH3COONa (aq) and CH3COOH (aq)
III.
HCOOK (aq) and HCOOH (aq)
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
Which titration curve is produced by the titration of 25 cm3 of 1.00 mol dm–3 NaOH with
1.00 mol dm–3 CH3COOH?
A.
B.
14
pH 7
0
14
pH 7
0
25
Volume of acid added / cm3
C.
pH 7
0
14
pH 7
25
Volume of acid added / cm3
2212-6113
Volume of acid added / cm3
D.
14
25
0
25
Volume of acid added / cm3
– 15 –
28.
M12/4/CHEMI/HPM/ENG/TZ2/XX
Consider the following reaction:
3Sn 2+ (aq ) + Cr2O7 2− (aq ) + 2 H + (aq ) → 2Cr 3+ (aq ) + 3SnO 2 (s) + H 2O (l)
Which statement is correct?
29.
A.
Sn2+ is the oxidizing agent because it undergoes oxidation.
B.
Sn2+ is the reducing agent because it undergoes oxidation.
C.
Cr2O72– is the oxidizing agent because it undergoes oxidation.
D.
Cr2O72– is the reducing agent because it undergoes oxidation.
What occurs during the operation of a voltaic cell based on the following overall reaction?
2Ag + (aq ) + Cu (s) → 2Ag (s) + Cu 2+ (aq )
30.
External circuit
Ion movement in solution
A.
electrons move from Cu (s) to Ag (s)
Ag+ (aq) move towards Cu (s)
B.
electrons move from Ag (s) to Cu (s)
Ag+ (aq) move towards Ag (s)
C.
electrons move from Cu (s) to Ag (s)
Ag+ (aq) move towards Ag (s)
D.
electrons move from Ag (s) to Cu (s)
Cu2+ (aq) move towards Cu (s)
Consider the following standard electrode potentials:
Sn 4+ (aq) + 2e −  Sn 2+ (aq)
E Ö = + 0.13 V
Pb 2+ (aq) + 2e –  Pb(s)
E Ö = − 0.13 V
What is the value of the cell potential, in V, for the spontaneous reaction that occurs when the two
half-cells are connected together?
A.
– 0.26
B.
0.00
C.
+0.13
D.
+0.26
2212-6113
Turn over
– 16 –
31.
32.
M12/4/CHEMI/HPM/ENG/TZ2/XX
Two electrolytic cells are connected in series and the same current passes through each cell. The first
cell contains silver electrodes in silver nitrate solution. The second cell contains copper electrodes
in copper(II) sulfate solution. In one experiment 1.00 g of silver is deposited in the first cell. What mass of copper, in g, is deposited in the second cell?
A.
1.00
107.87
B.
1.00
63.55
C.
1.00 63.55
×
107.87
2
D.
1.00
× 63.55
107.87
What is the name of (CH3)2CHCOCH3 applying IUPAC rules?
A.
3,3-dimethylpropan-2-one
B.
3-methylbutan-2-one
C.
2-methylbutan-3-one
D.
3-methylbutanal
2212-6113
– 17 –
33.
M12/4/CHEMI/HPM/ENG/TZ2/XX
The drug methadone contains several different functional groups. Which functional groups are
present in methadone?
CH3
H3C
H3C
H
34.
C
H
A.
ketone, benzene ring, amine
B.
ketone, benzene ring, amide
C.
aldehyde, alkene, amide
D.
aldehyde, alkene, amine
N
O
C
C
C
C
H
H
CH3
H
Which compound has the lowest boiling point?
A.
CH3CH2CH2OH
B.
CH3CH2CH2Br
C.
CH3CH2COOH
D.
CH3CH2CH2CH3
2212-6113
Turn over
– 18 –
35.
Which organic compounds, Q and P, are formed in the following two-stage reaction pathway?
Stage 1:
CH3(CH2)3Cl
NaOH(aq)

→
heat
Stage 2:
Q
2 7
→
reflux
Q
36.
M12/4/CHEMI/HPM/ENG/TZ2/XX
Cr O
2− (aq)/H + (aq)
Q
P
P
A.
CH3(CH2)3OH
CH3(CH2)3COOH
B.
CH3(CH2)3OH
CH3(CH2)2COOH
C.
CH3CH2CH=CH2
D.
CH3(CH2)3OH
no reaction product formed
CH3(CH2)2CHO
What is the organic product, Y, formed in the following reaction?
Ni
CH 3 (CH 2 )3 CN + 2H 2 
→Y
37.
A.
CH3(CH2)3NH2
B.
CH3(CH2)4NH2
C.
CH3(CH2)3CH3
D.
CH3(CH2)3COOH
What organic product is formed from the reaction of benzoic acid, C6H5COOH, with ethylamine,
CH3CH2NH2?
A.
C6H5CONHCH2CH3
B.
C6H5CONH2
C.
CH3CH2CONHC6H5
D.
C6H5COOCH2CH3
2212-6113
– 19 –
38.
39.
40.
M12/4/CHEMI/HPM/ENG/TZ2/XX
Which compound has a chiral carbon?
A.
Propan-2-ol
B.
1-bromo-2-methylbutane
C.
3-bromopentane
D.
Ethane-1,2-diol
What effect of optical isomers on plane-polarized light can be measured using a polarimeter?
A.
Reflection
B.
Emission
C.
Rotation
D.
Absorption
The relationship between the pressure, P, and the volume, V, of a fixed amount of gas at a
constant temperature is investigated experimentally. Which statements are correct?
I.
A graph of V against P will be a curve (non-linear).
II.
A graph of V against
III.
V = constant 
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
2212-6113
1
P
1
will be linear.
P
M12/4/CHEMI/HPM/ENG/TZ2/XX/M
MARKSCHEME
May 2012
CHEMISTRY
Higher Level
Paper 1
2 pages
–2–
M12/4/CHEMI/HPM/ENG/TZ2/XX/M
1.
D
16.
A
31.
C
46.
–
2.
B
17.
C
32.
B
47.
–
3.
A
18.
A
33.
A
48.
–
4.
C
19.
A
34.
D
49.
–
5.
A
20.
D
35.
B
50.
–
6.
B
21.
D
36.
B
51.
–
7.
B
22.
C
37.
A
52.
–
8.
C
23.
D
38.
B
53.
–
9.
B
24.
B
39.
C
54.
–
10.
D
25.
D
40.
D
55.
–
11.
A
26.
C
41.
–
56.
–
12.
A
27.
C
42.
–
57.
–
13.
D
28.
B
43.
–
58.
–
14.
C
29.
C
44.
–
59.
–
15.
D
30.
D
45.
–
60.
–
M12/4/CHEMI/HP2/ENG/TZ1/XX
22126108
CHEMISTRY
HIGHER level
Paper 2
Candidate session number
0
0
Examination code
Tuesday 8 May 2012 (afternoon)
2
2 hours 15 minutes
2
1
2
–
6
1
0
8
INSTRUCTIONS TO CANDIDATES
•
•
•
•
•
•
•
•
Write your session number in the boxes above.
Do not open this examination paper until instructed to do so.
Section A: answer all questions.
Section B:answer two questions.
Write your answers in the boxes provided.
A calculator is required for this paper.
A clean copy of the Chemistry Data Booklet is required for this paper.
The maximum mark for this examination paper is [90 marks].
35 pages
© International Baccalaureate Organization 2012
0136
–2–
M12/4/CHEMI/HP2/ENG/TZ1/XX
Section a
Answer all questions. Write your answers in the boxes provided.
1.
Propanone reacts with bromine in acidic solution according to the following equation.
+
H (aq)
CH 3COCH 3 (aq) + Br2 (aq) 
→ BrCH 2 COCH 3 (aq) + HBr (aq)
A student investigated the kinetics of this reaction using data logging equipment. Her data are
shown below.
A
B
C
D
E
F
–3
Initial concentration / mol dm
1
[CH3COCH3]
Time for colour Rate of reaction /
2 Experiment
[Br2] ± 0.0001 [H+] ± 0.0001 to fade / s ± 1
± 0.001
mol dm–3 s–1
3
1
0.200
0.0100
0.0500
250
4.00 ×10− 5
4
2
0.400
0.0100
0.0500
125
8.00 ×10− 5
5
3
0.200
0.0200
0.0500
500
4.00 ×10− 5
6
4
0.200
0.0100
0.1000
125
8.00 ×10− 5
7
5
0.400
0.0050
0.0500
63
X
8
(a)
(i)
Identify the reagent the student used to monitor the rate of reaction.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Calculate the rate of reaction for Experiment 5 and comment on the precision of
your result.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
0236
–3–
M12/4/CHEMI/HP2/ENG/TZ1/XX
(Question 1 continued)
[2]
(iii) Determine the percentage uncertainty in the calculated rate for Experiment 4.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
(i)
Deduce the order of reaction with respect to CH3COCH3, Br2 and H+.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Deduce the rate expression for the reaction. Calculate the rate constant and state
its units.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
0336
–4–
M12/4/CHEMI/HP2/ENG/TZ1/XX
(Question 1 continued)
(c)
The student proposed the following mechanism for this reaction.
Br2 → 2Br i
Slow
2Br i + CH 3COCH 3 → BrCH 2COCH 3 + HBr
Fast
Comment on whether or not the order with respect to bromine supports this hypothesis.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0436
[2]
–5–
2.
M12/4/CHEMI/HP2/ENG/TZ1/XX
In 1921 Thomas Midgley discovered that the addition of a lead compound could improve the
combustion of hydrocarbons in automobile (car) engines. This was the beginning of the use of
leaded gasoline (petrol).
The percentage composition, by mass, of the lead compound used by Midgley is shown below.
Mass composition / %
(a)
(i)
Pb
64.052
C
29.703
H
6.245
[3]
Determine the empirical formula of the lead compound.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Leaded gasoline has been phased out because the lead(IV) oxide, PbO2, produced
as a side product in the combustion reaction, may cause brain damage in children.
0.01 mol of Midgley’s lead compound produces 0.01 mol of lead(IV) oxide. Deduce the molecular formula of Midgley’s compound.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) Determine the equation for the complete combustion of Midgley’s compound.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
0536
–6–
M12/4/CHEMI/HP2/ENG/TZ1/XX
(Question 2 continued)
(b)
The combustion of unleaded gasoline still produces pollution with both local and global
consequences. Identify one exhaust gas which causes local pollution and one exhaust gas
which causes global pollution.
Local pollutant:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Global pollutant:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0636
[2]
–7–
3.
M12/4/CHEMI/HP2/ENG/TZ1/XX
Compound X (shown below) is produced by bacteria living in human armpits and is thought to
be partly responsible for unpleasant body smells.
(a)
Bromine water can be used to test for the presence of one of the functional groups in X.
Identify this functional group and describe the colour change observed.
H
H
H
C
H
H
H
H
C
C
H
[2]
H
O
H
C
C
C
C H
H
H
H
X
.......................................................................
.......................................................................
.......................................................................
.......................................................................
(b)
The other functional group changes when X is refluxed with acidified excess potassium
dichromate(VI) to produce a compound Y.
(i)
Identify the functional group present in Y but not in X.
[1]
..................................................................
..................................................................
(ii)
State the type of reaction that X undergoes to form Y.
[1]
..................................................................
..................................................................
(This question continues on the following page)
turn over
0736
–8–
M12/4/CHEMI/HP2/ENG/TZ1/XX
(Question 3 continued)
(c)
A different compound is produced if excess X is heated with acidified potassium
dichromate(VI) and the product Z is distilled off as it forms.
(i)
Identify the functional group present in Z but not in X.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Predict the order of increasing boiling point of the compounds X, Y and Z and
explain your answer.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0836
[3]
–9–
4.
M12/4/CHEMI/HP2/ENG/TZ1/XX
Chemical energy can be converted to electrical energy in the voltaic cell below.
e–
voltmeter
V
salt bridge
Fe
Mg
Mg2+ (aq)
(a)
Fe2+ (aq)
State the half-equation which describes the change at the Mg electrode and deduce which
metal is the positive electrode (cathode) of the cell.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
[1]
Deduce the equation for the overall reaction occurring in the cell.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
0936
– 10 –
M12/4/CHEMI/HP2/ENG/TZ1/XX
(Question 4 continued)
(c)
(i)
Define the term standard electrode potential.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Calculate the standard cell potential (E Ö ), in V, for the spontaneous reaction in (b),
using Table 14 of the Data Booklet.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
1036
– 11 –
M12/4/CHEMI/HP2/ENG/TZ1/XX
(Question 4 continued)
(d)
A different chemical change occurs when a saturated aqueous solution of magnesium
chloride is electrolysed using inert electrodes, S and T, in the circuit below.
–
+
A
S
T
MgCl2 (aq)
Different gases are produced at the electrodes S and T.
(i)
(ii)
[2]
State the half-equations for the reactions at each electrode.
S:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . T:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [1]
Determine the mole ratio in which the gases are formed.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
1136
– 12 –
M12/4/CHEMI/HP2/ENG/TZ1/XX
(Question 4 continued)
(iii) Suggest how the experimental conditions could be changed to produce the two
gases at a higher rate.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv) Another gas is produced when MgCl2 is at a lower concentration. State the name of
this gas and deduce the half-equation for this reaction.
Name:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Equation:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1236
[2]
– 13 –
M12/4/CHEMI/HP2/ENG/TZ1/XX
Section b
Answer two questions. Write your answers in the boxes provided.
5.
Ethane, C2H6, and disilane, Si2H6, are both hydrides of group 4 elements with similar structures
but with different chemical properties.
(a)
(i)
Deduce the Lewis (electron dot) structure for Si2H6 showing all valence electrons.
[1]
(ii)
State and explain the H–Si–H bond angle in Si2H6.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [1]
(iii) Identify the type of hybridization shown by the silicon atoms in Si2H6.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
1336
– 14 –
M12/4/CHEMI/HP2/ENG/TZ1/XX
(Question 5 continued)
(iv) State which of the bonds, Si–H or C–H, is more polar. Explain your choice.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (v)
Predict, with an explanation, the polarity of the two molecules.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (vi) Explain why disilane has a higher boiling point than ethane.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
1436
– 15 –
M12/4/CHEMI/HP2/ENG/TZ1/XX
(Question 5 continued)
(b)
Disilane undergoes complete oxidation to form silicon dioxide and water.
2Si 2 H 6 (g) +7O 2 (g) → 4SiO 2 (s) + 6H 2O (l)
(i)
The standard enthalpy of formation of the silicon compounds is given below.
ëH f Ö / kJ mol–1
+80
–911
Si2H6 (g)
SiO2 (s)
Calculate the standard enthalpy change, in kJ, for this reaction using these data
together with Table 12 of the Data Booklet.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Calculate the standard enthalpy change, in kJ, for the corresponding combustion
reaction of 2 moles of ethane, using Table 12 of the Data Booklet.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
1536
– 16 –
M12/4/CHEMI/HP2/ENG/TZ1/XX
(Question 5 continued)
(iii) Compare the structure and bonding in carbon dioxide and silicon dioxide.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (c)
Disilane reacts with hydrogen to produce silane, SiH4.
Si 2 H 6 (g) + H 2 (g) → 2SiH 4 (g)
Use values from Table 10 of the Data Booklet to calculate the enthalpy change, ëH Ö ,
for this reaction.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
1636
– 17 –
M12/4/CHEMI/HP2/ENG/TZ1/XX
(Question 5 continued)
(d)
Silicon tetrachloride, SiCl4, is a volatile colourless liquid first prepared by Jöns Jakob
Berzelius in 1823.
(i)
Suggest an approximate pH value for the solution formed by adding the chloride
to water and explain your answer. State the chemical equation for the reaction that
takes place.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Explain why the aqueous solution formed in (d) (i) conducts electricity whereas
liquid silicon tetrachloride does not.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
1736
– 18 –
Please do not write on this page.
Answers written on this page
will not be marked.
1836
M12/4/CHEMI/HP2/ENG/TZ1/XX
– 19 –
6.
M12/4/CHEMI/HP2/ENG/TZ1/XX
Consider the two equilibrium systems involving bromine gas illustrated below.
Piston
Bromine gas
Mixture of gaseous
hydrogen, bromine
and hydrogen bromide
Liquid bromine
A
(a)
B
State equations to represent the equilibria in A and B with Br2 (g) on the left-hand side in
both equilibria.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
(i)
Describe what you would observe if a small amount of liquid bromine is introduced
into A.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
1936
– 20 –
M12/4/CHEMI/HP2/ENG/TZ1/XX
(Question 6 continued)
(ii)
Predict what happens to the position of equilibrium if a small amount of hydrogen
is introduced into B.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) State and explain the effect of increasing the pressure in B on the position
of equilibrium.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (c)
(i)
Deduce the equilibrium constant expression, Kc, for the equilibrium in B.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
State the effect of increasing [H2] in B on the value of Kc.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
2036
– 21 –
M12/4/CHEMI/HP2/ENG/TZ1/XX
(Question 6 continued)
(d)
(i)
Hydrogen bromide forms a strong acid when dissolved in water whereas hydrogen
fluoride forms a weak acid. Distinguish between the terms strong acid and weak
acid. State equations to describe the dissociation of each acid in aqueous solution.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
2136
– 22 –
M12/4/CHEMI/HP2/ENG/TZ1/XX
(Question 6 continued)
(ii)
A student titrated 25.00 cm3 of a 0.100 mol dm–3 solution of hydrofluoric acid,
HF (aq), with 0.100 mol dm–3 NaOH (aq). Some of his data are presented below.
A
B
C
pH
14
2.88
3.08
3.39
3.57
3.71
3.82
3.90
3.98
4.05
4.11
4.17
4.22
4.27
4.32
4.36
4.40
4.44
4.48
4.52
4.56
4.59
4.63
4.66
4.70
4.73
4.77
4.80
4.84
4.87
12
D
E
F
G
H
1
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
10
8
pH
2
Volume of NaOH
(0.100 mol dm–3)
/ cm3
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
4.50
5.00
5.50
6.00
6.50
7.00
7.50
8.00
8.50
9.00
9.50
10.00
10.50
11.00
11.50
12.00
12.50
13.00
13.50
14.00
6
4
2
0
0.00
5.00 10.00 15.00 20.00 25.00 30.00 35.00 40.00 45.00 50.00
Volume of NaOH (0.100 mol dm–3) / cm3
(This question continues on the following page)
2236
– 23 –
M12/4/CHEMI/HP2/ENG/TZ1/XX
(Question 6 continued)
Two different data points can be used to determine a value for the pKa of HF (aq). Identify the data points and determine the pKa using two different calculations.
[6]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) Identify an indicator which could be used to find the equivalence point of the
titration using Table 16 of the Data Booklet and explain your choice.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
2336
– 24 –
M12/4/CHEMI/HP2/ENG/TZ1/XX
(Question 6 continued)
(e)
When bromine dissolves in water, 1 % of the original bromine molecules react according
to the following equation.
Br2 (aq) + H 2 O (l) HOBr (aq) + HBr (aq)
(i)
Deduce the oxidation numbers of bromine in the reactant and products.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
[1]
Explain the changes in the oxidation numbers of bromine.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) Estimate the magnitude of Kc for this reaction. Choose your value from the following
options:
Kc= 0
Kc < 1
Kc= 1
[1]
Kc > 1
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
2436
– 25 –
M12/4/CHEMI/HP2/ENG/TZ1/XX
(Question 6 continued)
(f)
Fluorine reacts with water to produce oxygen.
2F2 (g) + 2H 2 O (l) → 4HF(g) + O 2 (g)
(i)
[1]
Identify the oxidizing agent in the reaction.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
100 cm3 of fluorine gas is added to water. Calculate the volume of oxygen produced
at the same temperature and pressure.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
2536
– 26 –
7.
M12/4/CHEMI/HP2/ENG/TZ1/XX
A student prepared hex-1-ene, C6H12, from hexan-1-ol, C6H13OH, by a dehydration reaction.
C6 H13OH (l) → C6 H12 (l) + H 2 O (l)
The apparatus for this preparation is shown below. The reaction mixture contains 5.00 g of
hexan-1-ol and an excess of concentrated sulfuric acid, which removes the water from the
organic compound.
thermometer
water
condenser
reaction mixture
water bath
water
distillate containing
hex-1-ene with traces
of water
heat
The distillate was dried to obtain 2.62 g of hex-1-ene.
(a)
(i)
Determine the amount, in mol, of hexan-1-ol present in the reaction mixture.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
2636
– 27 –
M12/4/CHEMI/HP2/ENG/TZ1/XX
(Question 7 continued)
(ii)
[2]
Calculate the percentage yield of hex-1-ene produced.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) Another student repeated the experiment and reported a yield of 5.24 g of organic
product. Comment on this result.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
Hex-1-ene can also be produced from the reaction between 1-bromohexane and
concentrated aqueous sodium hydroxide or ethanolic sodium hydroxide with the reaction
being heated under reflux. Describe the mechanism of this reaction using curly arrows to
represent the movement of electron pairs.
[4]
(This question continues on the following page)
Turn over
2736
– 28 –
M12/4/CHEMI/HP2/ENG/TZ1/XX
(Question 7 continued)
(c)
(i)
Unlike 1-bromohexane, 2-bromohexane exists as a pair of optically active isomers. Draw diagrams to show the relationship between the two isomers of 2-bromohexane. [2]
(ii)
Outline briefly an experimental technique which could be used to distinguish the
two isomers in (c) (i).
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (d)
Identify the type of isomerism present in hex-2-ene.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
2836
– 29 –
M12/4/CHEMI/HP2/ENG/TZ1/XX
(Question 7 continued)
(e)
Both hex-2-ene and hex-1-ene can be converted to hexane by a reaction with hydrogen in
the presence of a nickel catalyst.
(i)
[3]
Deduce the names of three isomers of hexane.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Identify the compound with the molecular formula C6H14 which has the highest
boiling point and explain your choice.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
2936
– 30 –
M12/4/CHEMI/HP2/ENG/TZ1/XX
(Question 7 continued)
(f)
Hexane reacts with chlorine to form different products. The reactions can be represented
by the following equation, where R is an alkyl chain.
R–H + Cl2 → R–Cl + HCl
Describe the stepwise mechanism by giving one equation for each step and state the
essential condition in the initiation step.
Initiation:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Essential condition:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Propagation:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Termination:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3036
[4]
– 31 –
The element titanium is present in meteorites.
(a)
A meteorite was analysed using mass spectrometry (MS). The mass spectrum below
shows the relative abundances of the different titanium isotopes.
73.7 %
80
70
60
% Abundance
8.
M12/4/CHEMI/HP2/ENG/TZ1/XX
50
40
30
20
13.5 %
10
7.4 %
5.4 %
0
46
47
48
49
m/z
(i)
The first and last processes in mass spectrometry are vaporization and detection.
State the names of the other three processes in the order in which they happen and
outline how each occurs.
[5]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
3136
– 32 –
M12/4/CHEMI/HP2/ENG/TZ1/XX
(Question 8 continued)
(ii)
Define the term relative atomic mass (Ar).
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) Calculate the relative atomic mass of this sample of titanium, giving your answer to
one decimal place.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv) Explain why a very low pressure is maintained inside the mass spectrometer.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
3236
– 33 –
M12/4/CHEMI/HP2/ENG/TZ1/XX
(Question 8 continued)
The successive ionization energies of titanium are shown below.
Ionization energy / kJ mol–1
(b)
40 000
30 000
20 000
10 000
0
1
2
3
4
5
6
7
8
9
10 11 12 13
Electron removed
(i)
State the full electron configuration of an atom of titanium and identify the sub-level
from which the electron is removed when the 1st ionization energy is measured.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Explain why there are relatively large differences between the 4th and 5th,
and between the 10th and 11th ionization energies.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
3336
– 34 –
M12/4/CHEMI/HP2/ENG/TZ1/XX
(Question 8 continued)
(iii) Predict the three stable oxidation numbers of titanium ions in aqueous solution.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv) One characteristic of the d-block (transition) elements, like titanium, is that they
form coloured compounds. With reference to the colour wheel below, explain why
Ni2+ (aq) is green but Sc3+ (aq) is colourless.
[5]
yellow
orange
green
red
blue
violet
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
3436
– 35 –
M12/4/CHEMI/HP2/ENG/TZ1/XX
(Question 8 continued)
(c)
Successive ionization energy data provides evidence for the existence of energy levels
in atoms. Other evidence is provided by the hydrogen emission spectrum.
(i)
[2]
Describe the appearance of the visible emission spectrum of hydrogen.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Explain how this spectrum is related to the electron energy levels in a hydrogen atom.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
3536
Please do not write on this page.
Answers written on this page
will not be marked.
3636
M12/4/CHEMI/HP2/ENG/TZ1/XX/M
MARKSCHEME
May 2012
CHEMISTRY
Higher Level
Paper 2
17 pages
–2–
M12/4/CHEMI/HP2/ENG/TZ1/XX/M
This markscheme is confidential and for the exclusive use of
examiners in this examination session.
It is the property of the International Baccalaureate and must not
be reproduced or distributed to any other person without the
authorization of IB Cardiff.
–3–
M12/4/CHEMI/HP2/ENG/TZ1/XX/M
General Marking Instructions
Assistant Examiners (AEs) will be contacted by their team leader (TL) through Scoris™, by e-mail
or telephone – if through Scoris™ or by e-mail, please reply to confirm that you have downloaded
the markscheme from IBIS. The purpose of this initial contact is to allow AEs to raise any queries
they have regarding the markscheme and its interpretation. AEs should contact their team leader
through Scoris™ or by e-mail at any time if they have any problems/queries regarding marking.
For any queries regarding the use of Scoris™, please contact emarking@ibo.org.
If you have any queries on administration please contact:
Rachel Bengough
Subject Operations
IB Assessment Centre
Peterson House
Malthouse Avenue
Cardiff Gate
Cardiff CF23 8GL
GREAT BRITAIN
Tel: +(44) 29 2054 7777
Fax: +(44) 29 2054 7778
E-mail: rachel.bengough@ibo.org
–4–
M12/4/CHEMI/HP2/ENG/TZ1/XX/M
1.
Follow the markscheme provided, award only whole marks and mark only in RED.
2.
Make sure that the question you are about to mark is highlighted in the mark panel on the right-hand
side of the screen.
3.
Where a mark is awarded, a tick/check () must be placed in the text at the precise point where it
becomes clear that the candidate deserves the mark. One tick to be shown for each mark awarded.
4.
Sometimes, careful consideration is required to decide whether or not to award a mark. In these
cases use Scoris™ annotations to support your decision. You are encouraged to write comments
where it helps clarity, especially for re-marking purposes. Use a text box for these additional
comments. It should be remembered that the script may be returned to the candidate.
5.
Personal codes/notations are unacceptable.
6.
Where an answer to a part question is worth no marks but the candidate has attempted the part
question, enter a zero in the mark panel on the right-hand side of the screen. Where an answer to a
part question is worth no marks because the candidate has not attempted the part question, enter an
“NR” in the mark panel on the right-hand side of the screen.
7.
If a candidate has attempted more than the required number of questions within a paper or section
of a paper, mark all the answers. Scoris™ will only award the highest mark or marks in line with
the rubric.
8.
Ensure that you have viewed every page including any additional sheets. Please ensure that you
stamp ‘seen’ on any page that contains no other annotation.
9.
Mark positively. Give candidates credit for what they have achieved and for what they have got
correct, rather than penalizing them for what they have got wrong. However, a mark should not be
awarded where there is contradiction within an answer. Make a comment to this effect using a text
box or the “CON” stamp.
–5–
M12/4/CHEMI/HP2/ENG/TZ1/XX/M
Subject Details: Chemistry HL Paper 2 Markscheme
Mark Allocation
Candidates are required to answer ALL questions in Section A [40 marks] and TWO questions in
Section B [2 x 25 marks]. Maximum total = [90 marks].
1.
A markscheme often has more marking points than the total allows. This is intentional.
2.
Each marking point has a separate line and the end is shown by means of a semicolon (;).
3.
An alternative answer or wording is indicated in the markscheme by a slash (/). Either wording can
be accepted.
4.
Words in brackets ( ) in the markscheme are not necessary to gain the mark.
5.
Words that are underlined are essential for the mark.
6.
The order of marking points does not have to be as in the markscheme, unless stated otherwise.
7.
If the candidate’s answer has the same “meaning” or can be clearly interpreted as being of
equivalent significance, detail and validity as that in the markscheme then award the mark.
Where this point is considered to be particularly relevant in a question it is emphasized by
OWTTE (or words to that effect).
8.
Remember that many candidates are writing in a second language. Effective communication is more
important than grammatical accuracy.
9.
Occasionally, a part of a question may require an answer that is required for subsequent
marking points. If an error is made in the first marking point then it should be penalized. However,
if the incorrect answer is used correctly in subsequent marking points then follow through marks
should be awarded. When marking, indicate this by adding ECF (error carried forward) on the
script.
10.
Do not penalize candidates for errors in units or significant figures, unless it is specifically referred
to in the markscheme.
11.
If a question specifically asks for the name of a substance, do not award a mark for a correct
formula unless directed otherwise in the markscheme, similarly, if the formula is specifically asked
for, unless directed otherwise in the markscheme do not award a mark for a correct name.
12.
If a question asks for an equation for a reaction, a balanced symbol equation is usually expected, do
not award a mark for a word equation or an unbalanced equation unless directed otherwise in the
markscheme.
13.
Ignore missing or incorrect state symbols in an equation unless directed otherwise in the
markscheme.
–6–
M12/4/CHEMI/HP2/ENG/TZ1/XX/M
SECTION A
1.
(a)
(i)
bromine/Br2;
Do not allow Br or bromide/Br–.
(ii)
7.9 105 (mol dm–3 s–1);
The number of significant figures must be correct.
Allow 8.0  10 5 (mol dm–3 s–1).
(only 2 significant figures) because of precision of time/[Br 2] measurements;
Allow answers based on rate laws or orders of reaction.
M2 can only be scored if M1 correct.
(iii) [Br2]: 1% and Time: 0.8%;
Percentage Uncertainty: 1.8%;
Accept Percentage Uncertainty: 2%.
Do not allow answers based on rate laws or orders of reaction.
(b)
(i)
(ii)
CH3COCH3: 1;
Br2: 0;
H+: 1;
rate = k [H+] [CH3COCH3];
k = 4.00 10–3 ;
mol–1 dm3 s–1;
[1]
[2]
[2]
[3]
[3]
(c) (no it doesn’t) actual reaction is zero order with respect to Br 2;
(no it doesn’t) actual rate determining step/slow step does not involve Br2 / OWTTE;
OR
(no it doesn’t) reaction is first order with respect to H+;
(no it doesn’t) mechanism/rate determining step/slow step does not involve H + /
OWTTE;
OR
(no it doesn’t) reaction is first order with respect to CH3COCH3;
(no it doesn’t) rate determining step/slow step does not involve CH 3COCH3 /
OWTTE;
Award no marks if yes stated.
[2]
–7–
2.
(a)
(b)
(i)
M12/4/CHEMI/HP2/ENG/TZ1/XX/M
 64.052 
n(Pb): 
  0.30915 (mol)
 207.19 
 29.703 
n(C): 
  2.473 (mol)
 12.01 
 6.245 
n(H): 
  6.18 (mol)
 1.01 
Do not penalize if integer values of atomic masses used.
Accept alternative calculation method.
Award [2] for three correct.
Award [1] for any two correct.
PbC8H20;
[3]
(ii)
PbC8H20;
[1]
(iii)
PbC8H20  14O2  PbO2  8CO2  10H2O
correct reactants and products;
correct coefficients;
M2 can only be scored if M1 correct.
[2]
Local pollutant:
carbon monoxide/CO / volatile organics/VOCs / nitrogen oxide/NO / (unburnt)
hydrocarbons;
Do not accept methane/CH4, ethane/C2H6, propane/C3H8 or butane/C4H10.
Global pollutant:
nitrogen oxide/NO / carbon dioxide/CO2;
Accept nitrogen dioxide/NO2 / NOx for both local or global pollutant.
Accept other widely used names for NO such as nitric oxide/nitrogen
monoxide/nitrogen(II) oxide or nitrogen(IV) oxide for NO2.
[2]
–8–
3.
(a)
(b)
(c)
M12/4/CHEMI/HP2/ENG/TZ1/XX/M
(carbon to carbon) double bond / alkene;
Accept if identified on diagram.
orange/brown/red/yellow to colourless / bromine is decolourized;
M2 can be only scored if M1 correct.
[2]
(i)
COOH/CO2H / carboxylic acid / alkanoic acid;
Do not allow carboxylic/alkanoic, carbonyl or carboxylate.
[1]
(ii)
redox / oxidation (of alcohol);
[1]
(i)
aldehyde / alkanal / CHO;
Accept C=O / carbonyl.
[1]
(ii)
Z < X < Y;
Accept Z,X,Y or ZXY.
no hydrogen bonding in Z / hydrogen bonding in X and Y;
Accept statements such as Z has only van der Waals/London/dispersion
forces and dipole-dipole forces.
Y most polar / more electrons / forms dimers / forms two hydrogen bonds /
greater molecular/molar mass;
Do not accept Y has a larger mass.
[3]
–9–
4.
M12/4/CHEMI/HP2/ENG/TZ1/XX/M
Mg(s)  Mg2 (aq)  2e ;
Fe/iron;
Do not accept Fe/Fe2+half-equation or Fe2+.
[2]
(b)
Mg(s)  Fe2 (aq)  Mg2 (aq)  Fe(s) ;
[1]
(c)
(i)
(a)
(d)
(potential of reduction half-reaction) under standard conditions measured
relative to standard hydrogen electrode/SHE / difference of standard
reduction potential of substance undergoing reduction and standard
reduction potential of substance undergoing oxidation / OWTTE;
[1]
(ii)
(+)1.92 (V);
[1]
(i)
S: 2H 2O(l)  2e –  H 2 (g)  2OH – (aq) / 2H  (aq)  2e –  H 2 (g) ;
(ii)
T: 2Cl– (aq)  Cl2 (g)  2e – ;
[2]
1:1;
[1]
(iii) increase in current/voltage/surface area of electrodes;
[1]
(iv) oxygen;
2H 2O  O2  4H   4e – / 4OH –  2H 2O  O2  4e – ;
[2]
– 10 –
M12/4/CHEMI/HP2/ENG/TZ1/XX/M
SECTION B
5.
(a)
(i)
;
[1]
Accept any combination of lines, dots or crosses to represent electron pairs.
(ii)
109 / 109.5 / 109 28' ;
four/tetrahedrally
arranged
negative
charge
centres/electron
domains/electron pairs (around central/silicon atom) / equal repulsion
between bonding pairs (around central/silicon atom) / OWTTE;
M2 is an independent marking point.
Reference must be made to negative or electron.
Do not accept tetrahedral molecule.
[2]
(iii) sp3;
[1]
(iv) C–H;
larger difference in electronegativity (for C–H bond) / smaller difference in
electronegativity (for Si–H bond) / EN (CH) = 0.4 and EN (SiH) = 0.3;
[2]
(v)
both (molecules) non-polar;
both (molecules) symmetrical / polar bond effects cancel out / OWTTE;
[2]
(vi) stronger/larger/greater van der Waals’/London/dispersion forces;
Do not accept stronger/larger/greater intermolecular forces.
more electrons / stronger instantaneous dipole;
Do not accept larger mass.
(b)
(i)
[2]
(  ë H f (products) = ) –5360 (kJ);
Ö
(  ë H f (reactants) = ) +160 (kJ);
= –5520 (kJ);
[3]
(–1560  2 =) –3120 (kJ);
[1]
Ö
(ii)
(iii) Structure:
CO2 molecular and SiO2 three-dimensional/network/giant lattice/giant
covalent/macromolecular/repeating tetrahedral units;
CO2 linear and SiO2 tetrahedral;
Intramolecular Bonding:
covalent bonds in CO2 and SiO2;
double bonds in CO2 and single bonds in SiO2;
Accept diagrams showing bonding types (double and single) within the
structures.
[3 max]
– 11 –
(c)
M12/4/CHEMI/HP2/ENG/TZ1/XX/M
Bonds broken:
6Si–H, Si–Si, H–H / (+)2570 (kJ);
Bonds formed:
8Si–H / (–)2544 (kJ);
+26 (kJ);
OR
Bonds broken:
Si–Si, H–H / (+)662 (kJ);
Bonds formed:
2Si–H / (–)636 (kJ);
+26 (kJ);
(d) (i)
1 to 3;
Accept any answer in this range: pH ≤ 3.
HCl/strong acid formed;
SiCl4 (l)  4H2O(l)  Si(OH)4 (s)  4HCl(aq) ;
(ii)
[3]
[3]
Aqueous solution:
mobile ions/charged particles present;
Liquid:
molecular covalent / no (mobile) charged particles/ions;
[2]
– 12 –
6.
(a)
Br2 (g)
Br2 (l) ;
H2 (g)  Br2 (g)
(b)
M12/4/CHEMI/HP2/ENG/TZ1/XX/M
2HBr (g) ;
(i)
increase volume of liquid / no change of colour of vapour;
[1]
(ii)
shifts to right/toward products/forward reaction favoured;
Accept reverse statement if process written the other way around.
Answer must match stated equation.
[1]
(iii) no effect;
same amounts/number of (gaseous) moles/molecules on both sides;
(c)
(d)
[2]
[2]
(i)
[HBr]2
;
( K c )
[H 2 ][Br2 ]
[1]
(ii)
no effect (only depends on the temperature);
[1]
(i)
Strong acid: acid/electrolyte (assumed to be almost) 100%/completely
dissociated/ionized (in solution/water) / OWTTE and Weak acid:
acid/electrolyte only partially/slightly dissociated/ionized (in solution/water)
/ OWTTE;
HBr (aq)  H (aq)  Br  (aq) ;
HF(aq)
H (aq)  F (aq) ;
[3]
(ii)
Data points:
(0.00, 2.88) and (12.50, 4.77);
For first point also accept volume = 0.00 with pH in range 2.8–2.9.
For second point also accept either:
volume in range between 12.5–12.6 and pH 4.8–4.9
OR
volume in range between 25.0–25.2 and pH 8.0–10.0
For (0.00, 2.88):
[H+] = [F–];
pKa = 2pH –1 / K a 
[H  ]2
;
0.100
For (12.50, 4.77):
[HF] = [F–];
pKa = pH;
pKa = 4.77;
Accept any value in range 4.7–4.9 if consistent with data points.
Accept alternative calculation method if other data points from the table or
graph are used and the pKa in correct range.
(iii) bromothymol blue / phenol red / phenolphthalein;
pKa/end point of indicator in range 7–10 as pH at equivalence in range 7–10;
[6]
[2]
– 13 –
(e)
(i)
(ii)
(f)
7.
(a)
M12/4/CHEMI/HP2/ENG/TZ1/XX/M
Br2: 0
HBr: –1
HOBr: +1
Award [2] for three correct.
Award [1] for any two correct.
[2]
bromine is oxidized and reduced / disproportionation;
[1]
(iii) Kc < 1;
[1]
(i)
F2/fluorine;
Do not allow F.
[1]
(ii)
50 (cm3) / 0.050 dm3 ;
[1]
(i)
molar mass = 102.20 (g mol–1);
5.00
amount (=
) = 0.0489 (mol);
102.20
(ii)
theoretical yield = (84.18  0.0489 =) 4.12 (g);
 2.62

 100   63.6 % ;
percentage yield  
 4.12

Accept alternative calculation method.
[2]
[2]
(iii) yield above 100% not possible / experimental yield > theoretical yield /
OWTTE;
Must have reference to a final yield.
sample contaminated with hexan-1-ol/water / inadequate drying / OWTTE;
Do not accept error in reading balance/weighing scale.
[2]
– 14 –
M12/4/CHEMI/HP2/ENG/TZ1/XX/M
(b)
OR
curly arrow going from lone pair/negative charge on O in HO– to H on β-C;
Do not allow curly arrow originating on H in HO–.
curly arrow going from CH bond to form C=C bond;
curly arrow showing Br leaving;
formation of organic product H2C=CH(C4H9) and H2O and Br–;
[4]
– 15 –
(c)
M12/4/CHEMI/HP2/ENG/TZ1/XX/M
(i)
[2]
(ii)
use a polarimeter / polarimetry;
isomers rotate plane of polarized light in equal, but opposite directions;
(d)
geometric / cis-trans / E-Z;
(e)
(i)
(ii)
2-methylpentane;
3-methylpentane;
2,2-dimethylbutane;
2,3-dimethylbutane;
[1]
[3 max]
hexane;
Accept the molecular structure, full structural formula or condensed
structural formula.
straight chain/no branches, hence increased surface area/more closely packed;
stronger/larger/greater London/dispersion/van der Waals’;
Accept the opposite arguments.
Do not accept stronger/larger/greater intermolecular forces.
(f)
[2]
[3]
Initiation:
Cl2  2Cl ;
Essential condition:
UV/sunlight/hf/h;
Propagation:
Cl  R–H  HCl  R / R  Cl2  RCl  Cl ;
Termination:
Cl  Cl  Cl2 / Cl  R  RCl / R  R  R 2 ;
Allow more specific detail of R based on hexane (e.g. CH3(CH2)4CH2–H) in
mechanistic steps.
[4]
– 16 –
8.
(a)
(i)
M12/4/CHEMI/HP2/ENG/TZ1/XX/M
ionization, acceleration, deflection/separation
Award [1] for all three names and [1] for correct order.
Award [1] for two names in correct order.
Ionization:
sample bombarded with (high-energy/high-speed) electrons / OWTTE;
Acceleration:
electric field/oppositely charged plates;
Deflection:
(electro)magnet/magnetic field;
(ii)
ratio of average/mean mass of an atom to the mass of C-12 isotope /
average/mean mass of an atom on a scale where one atom of C-12 has a
mass of 12 / sum of the weighted average/mean mass of isotopes of an
element compared to C-12 / OWTTE;
Award no mark if “element” is used instead of “atom”.
(46 13.5)  (47  7.4)  (48  73.7)  (49  5.4)
;
100
47.7;
Accept atomic mass units but award [1 max] if other units given.
Answer must be given to one decimal place.
[5]
[1]
(iii) Ar =
(iv) prevents collisions/unintentional deflections / OWTTE;
(b)
(i)
(ii)
1s2 2s2 2p6 3s2 3p6 4s2 3d2;
4s;
[2]
[1]
[2]
4th electron removed from 3d and 5th electron removed from 3p;
10th electron removed from 3p and 11th electron removed from 3s;
Accept either of the following answers for the third mark:
electrons removed from lower energy level / energy level closer to nucleus
are attracted more strongly;
greater effective nuclear charge / s electrons more penetrating;
[3 max]
(iii) +2, +3, +4;
[1]
(iv) (colour) due to partially filled/incomplete d sub-level/orbital;
d sub-level is split / d orbitals are split;
Ni2+(aq) has incomplete 3d sub-level/orbital but Sc3+(aq) has no 3d
electron/empty/d sub-level;
electrons move from lower to higher (sub)levels when they absorb
energy/light;
Ni2+(aq) (appears green because it) absorbs red;
[5]
– 17 –
(c)
(i)
(ii)
M12/4/CHEMI/HP2/ENG/TZ1/XX/M
line spectrum;
(lines) converge at high energy/frequency/shorter wave length/blue end of
spectrum;
Both marks can be awarded if suitable diagram is given.
electron transition from higher to lower/second energy levels;
each transition causes emission of light of specific frequency/wavelength/
energy;
hf / hv / hc
each transition/line is related to energy difference / ∆ E 
;
λ
energy levels in hydrogen atom are closer/converge at higher energy;
[2]
[3 max]
M12/4/CHEMI/HP2/ENG/TZ2/XX
22126114
CHEMISTRY
HIGHER level
Paper 2
Candidate session number
0
0
Examination code
Tuesday 8 May 2012 (afternoon)
2
2 hours 15 minutes
2
1
2
–
6
1
1
4
INSTRUCTIONS TO CANDIDATES
•
•
•
•
•
•
•
•
Write your session number in the boxes above.
Do not open this examination paper until instructed to do so.
Section A: answer all questions.
Section B:answer two questions.
Write your answers in the boxes provided.
A calculator is required for this paper.
A clean copy of the Chemistry Data Booklet is required for this paper.
The maximum mark for this examination paper is [90 marks].
30 pages
© International Baccalaureate Organization 2012
0132
–2–
M12/4/CHEMI/HP2/ENG/TZ2/XX
Section a
Answer all questions. Write your answers in the boxes provided.
Hydrogen peroxide, H2O2 (aq), releases oxygen gas, O2 (g), as it decomposes according to the
equation below.
2H 2 O 2 (aq ) → 2H 2 O (l) + O 2 (g )
50.0 cm3 of hydrogen peroxide solution was placed in a boiling tube, and a drop of liquid
detergent was added to create a layer of bubbles on the top of the hydrogen peroxide solution
as oxygen gas was released. The tube was placed in a water bath at 75 °C and the height of
the bubble layer was measured every thirty seconds. A graph was plotted of the height of the
bubble layer against time.
6.0
Height of bubble layer / mm
1.
5.0
4.0
3.0
2.0
1.0
0.0
(a)
0
30
60
90
120 150 180 210 240 270 300
Time / s
[1]
Explain why the curve reaches a maximum.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
0232
–3–
M12/4/CHEMI/HP2/ENG/TZ2/XX
(Question 1 continued)
(b)
[3]
Use the graph to calculate the rate of decomposition of hydrogen peroxide at 120 s.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (c)
The decomposition of hydrogen peroxide to form water and oxygen is a redox reaction.
(i)
Deduce the oxidation numbers of oxygen present in each of the species below.
Species
[2]
Oxidation number of oxygen
H2O2
H2O
O2
(ii)
[2]
State two half-equations for the decomposition of hydrogen peroxide.
Oxidation:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reduction:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
0332
–4–
2.
M12/4/CHEMI/HP2/ENG/TZ2/XX
A student added 7.40 ×10−2 g of magnesium ribbon to 15.0 cm3 of 2.00 mol dm–3
hydrochloric acid. The hydrogen gas produced was collected using a gas syringe at 20.0 °C
and 1.01×105 Pa.
(a)
State the equation for the reaction between magnesium and hydrochloric acid.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
[3]
Determine the limiting reactant.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (c)
Calculate the theoretical yield of hydrogen gas:
(i)
[1]
in mol.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
in cm3, under the stated conditions of temperature and pressure.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
0432
–5–
M12/4/CHEMI/HP2/ENG/TZ2/XX
(Question 2 continued)
(d)
The actual volume of hydrogen measured was lower than the calculated theoretical volume. Suggest two reasons why the volume of hydrogen gas obtained was less.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
0532
–6–
3.
M12/4/CHEMI/HP2/ENG/TZ2/XX
Lattice enthalpies can be determined experimentally using a Born–Haber cycle and theoretically
using calculations based on electrostatic principles.
(a)
The experimental lattice enthalpies of the chlorides of lithium, LiCl, sodium, NaCl,
potassium, KCl, and rubidium, RbCl, are given in Table 13 of the Data Booklet. Explain the trend in the values.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
Explain why magnesium chloride, MgCl2, has a much greater lattice enthalpy than
sodium chloride, NaCl.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
0632
–7–
M12/4/CHEMI/HP2/ENG/TZ2/XX
(Question 3 continued)
(c)
(i)
Identify the process labelled a on the Born–Haber cycle for the determination
of the standard enthalpy of formation of lithium fluoride, LiF.
[1]
..................................................................
Li + (g ) + e − + F (g)
Li (g ) + F (g )
Li + (g ) + F− (g )
Li (g ) + 12 F2 (g )
a
Li (s) + 12 F2 (g )
LiF (s)
(ii)
The enthalpy change for process a is +159 kJ mol−1. Calculate the standard
enthalpy of formation of lithium fluoride, LiF, using this and other values from the
Data Booklet.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
0732
–8–
4.
M12/4/CHEMI/HP2/ENG/TZ2/XX
Draw the Lewis structures, predict the shape and deduce the bond angles for xenon tetrafluoride
and the nitrate ion.
Species
Lewis structure
Shape
XeF4
NO3–
0832
Bond angle
[6]
–9–
5.
(a)
M12/4/CHEMI/HP2/ENG/TZ2/XX
131
I is a radioactive isotope of iodine.
(i)
Define the term isotope.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Identify one use of iodine-131 in medicine and explain why it is potentially
dangerous.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
[3]
Discuss the use of carbon-14 in carbon dating.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
0932
– 10 –
Please do not write on this page.
Answers written on this page
will not be marked.
1032
M12/4/CHEMI/HP2/ENG/TZ2/XX
– 11 –
6.
M12/4/CHEMI/HP2/ENG/TZ2/XX
State and explain whether solutions of each of the following compounds are acidic, basic
or neutral.
[4]
Cr(NO3)3:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CH3COONH4:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
1132
– 12 –
M12/4/CHEMI/HP2/ENG/TZ2/XX
Section b
Answer two questions. Write your answers in the boxes provided.
7.
(a)
An organic compound, X, with a molar mass of approximately 88 g mol–1 contains
54.5 % carbon, 36.3 % oxygen and 9.2 % hydrogen by mass.
(i)
Distinguish between the terms empirical formula and molecular formula.
[2]
Empirical formula:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Molecular formula:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Determine the empirical formula of X.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) Determine the molecular formula of X.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
1232
– 13 –
M12/4/CHEMI/HP2/ENG/TZ2/XX
(Question 7 continued)
(iv) X is a straight-chain carboxylic acid. Draw its structural formula.
(v)
[1]
Draw the structural formula of an isomer of X which is an ester.
[1]
(vi) The carboxylic acid contains two different carbon-oxygen bonds. Identify which
bond is stronger and which bond is longer.
[2]
Stronger bond:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Longer bond:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
1332
– 14 –
M12/4/CHEMI/HP2/ENG/TZ2/XX
(Question 7 continued)
(vii) Predict and explain the bond lengths and bond strengths of the carbon-oxygen
bonds in CH3CH2COO−.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
(i)
State the meaning of the term hybridization.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Describe the hybridization of the carbon atom in methane and explain how the
concept of hybridization can be used to explain the shape of the methane molecule.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
1432
– 15 –
M12/4/CHEMI/HP2/ENG/TZ2/XX
(Question 7 continued)
(iii) Identify the hybridization of the carbon atoms in diamond and graphite and explain
why graphite is an electrical conductor.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (c)
(i)
Aluminium chloride, Al2Cl6, does not conduct electricity when molten but
aluminium oxide, Al2O3, does. Explain this in terms of the structure and bonding
of the two compounds.
[4]
Al2Cl6:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Al2O3:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
[2]
Describe the reaction between aluminium chloride and water.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
1532
– 16 –
8.
(a)
M12/4/CHEMI/HP2/ENG/TZ2/XX
The equation for the reaction between sodium hydroxide, NaOH, and nitric acid, HNO3,
is shown below.
NaOH (aq ) + HNO3 (aq ) → NaNO3 (aq ) + H 2 O (l)
∆H = −57.6 kJ mol−1
(i)
Sketch and label an enthalpy level diagram for this reaction.
[3]
(ii)
Deduce whether the reactants or the products are more energetically stable,
stating your reasoning.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) Calculate the change in heat energy, in kJ, when 50.0 cm3 of 2.50 mol dm–3
sodium hydroxide solution is added to excess nitric acid.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
1632
– 17 –
M12/4/CHEMI/HP2/ENG/TZ2/XX
(Question 8 continued)
(b)
When ammonium chloride, NH4Cl (aq), is added to excess solid sodium carbonate,
Na2CO3 (s), an acid–base reaction occurs. Bubbles of gas are produced and the
solid sodium carbonate decreases in mass. State one difference which would be
observed if nitric acid, HNO3 (aq), was used instead of ammonium chloride.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (c)
When 5.35 g ammonium chloride, NH4Cl (s), is added to 100.0 cm3 of water,
the temperature of the water decreases from 19.30 °C to 15.80 °C. Determine the
enthalpy change, in kJ mol−1, for the dissolving of ammonium chloride in water.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
1732
– 18 –
M12/4/CHEMI/HP2/ENG/TZ2/XX
(Question 8 continued)
(d)
A solution of ammonia has a concentration of 0.500 mol dm–3.
Calculate the pH of the ammonia solution using information from Table 15 of the
Data Booklet. State one assumption made.
[4]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (e)
A buffer solution is made using 25.0 cm3 of 0.500 mol dm–3 nitric acid, HNO3 (aq),
and 25.0 cm3 of 1.00 mol dm–3 ammonia solution, NH3 (aq).
(i)
State the meaning of the term buffer solution.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Calculate the concentrations of ammonia and ammonium ion in the buffer solution.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
1832
– 19 –
M12/4/CHEMI/HP2/ENG/TZ2/XX
(Question 8 continued)
[2]
(iii) Determine the pH of the buffer solution at 25 °C.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv) Explain why the pH of the buffer solution is different from the pH of the ammonia
solution calculated in (d).
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (v)
Explain the action of the buffer solution when a few drops of nitric acid solution
are added to it.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
1932
– 20 –
M12/4/CHEMI/HP2/ENG/TZ2/XX
(Question 8 continued)
(f)
Bromocresol green is an acid–base indicator. Information about bromocresol green is
given in Table 16 of the Data Booklet.
(i)
Identify the property of bromocresol green that makes it suitable to use as an
acid–base indicator.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
State and explain the relationship between the pH range of bromocresol green and
its pKa value.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2032
[2]
– 21 –
9.
(a)
M12/4/CHEMI/HP2/ENG/TZ2/XX
Transition metals exhibit variable oxidation states in their complexes.
(i)
State the full electron configuration of Fe.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
State the abbreviated electron configuration of Fe3+ ions.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) Cyanide ions, CN−, can act as ligands. One complex ion that involves the cyanide
ion is [Fe(CN)6]3−. Identify the property of a cyanide ion which allows it to act as
a ligand, and explain the bonding that occurs in the complex ion in terms of
acid–base theory. Describe the structure of the complex ion, [Fe(CN)6]3−.
[4]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
2132
– 22 –
M12/4/CHEMI/HP2/ENG/TZ2/XX
(Question 9 continued)
(iv) Explain why complexes of Fe3+ are coloured.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
The Contact process converts SO2 (g) to SO3 (g) during the production of sulfuric acid. The reaction is exothermic.
(i)
State the equation for the production of SO3 (g) from SO2 (g).
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Identify a catalyst used in the Contact process.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) Explain the effect of the catalyst on the reaction rate.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
2232
– 23 –
M12/4/CHEMI/HP2/ENG/TZ2/XX
(Question 9 continued)
(iv) Catalysts are very expensive. Suggest two economic benefits of using the catalyst
to speed up the reaction in the Contact process.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (v)
Predict and explain whether entropy increases or decreases during the formation
of SO3.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (vi) State and explain whether the formation of SO3 is more spontaneous or less
spontaneous at higher temperatures.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
2332
– 24 –
M12/4/CHEMI/HP2/ENG/TZ2/XX
(Question 9 continued)
(c)
The reaction between carbon monoxide, CO (g), and nitrogen dioxide, NO2 (g),
1
was studied at different temperatures and a graph was plotted of ln k against .
T
The equation of the line of best fit was found to be:
1
ln k = −1.60 ×104   + 23.2
T 
4.000
3.000
2.000
1.000
0.000
ln k –1.000
–2.000
–3.000
– 4.000
–5.000
–6.000
0.0
0.5
1.0
1.5
2.0
1
/ 10–3 K–1
T
(This question continues on the following page)
2432
– 25 –
M12/4/CHEMI/HP2/ENG/TZ2/XX
(Question 9 continued)
(i)
(ii)
The Arrhenius equation is shown in Table 1 of the Data Booklet. Identify the
symbols k and A.
k:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Calculate the activation energy, Ea, for the reaction between CO (g) and NO2 (g).
[2]
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [2]
(iii) Calculate the numerical value of A.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
2532
– 26 –
10.
(a)
M12/4/CHEMI/HP2/ENG/TZ2/XX
Esters and amides can be produced by condensation reactions.
(i)
State the names of two organic compounds required to produce ethyl methanoate
and state suitable reaction conditions.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Deduce the structure of the simplest repeating unit of the polymer formed from the
reaction between 1,6-diaminohexane and hexane-1,6-dioic acid and state one use of
this product.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
2632
– 27 –
M12/4/CHEMI/HP2/ENG/TZ2/XX
(Question 10 continued)
(b)
Under certain conditions but-2-ene can react with water to form butan-2-ol.
(i)
[1]
Identify a suitable catalyst for this reaction.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
But-2-ene can be converted to 2-bromobutane and then to butan-2-ol as follows:
CH 3CH=CHCH3 i
→ CH 3CH(Br)CH 2 CH 3 ii
→ CH 3CH(OH)CH 2 CH 3
Identify the reagent(s) and conditions necessary for each of the steps I and II.
[4]
Step I:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Step II:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) State and explain how the rate of step II would differ if 2-chlorobutane was used
instead of 2-bromobutane.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
2732
– 28 –
M12/4/CHEMI/HP2/ENG/TZ2/XX
(Question 10 continued)
(c)
Halogenoalkanes can be classified as primary, secondary or tertiary.
(i)
State the meaning of the term isomers.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Deduce the structural formulas of 2-bromobutane and 1-bromo-2-methylpropane,
and identify each molecule as primary, secondary or tertiary.
[4]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
2832
– 29 –
M12/4/CHEMI/HP2/ENG/TZ2/XX
(Question 10 continued)
(d)
1-bromopropane undergoes a substitution reaction with potassium cyanide.
CH2CH3
*C
H
H
(i)
Br
[1]
Explain why the substitution occurs on the carbon atom that is marked as *C.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Explain the mechanism of the reaction using curly arrows to represent the
movement of electron pairs during the substitution.
[4]
(This question continues on the following page)
Turn over
2932
– 30 –
M12/4/CHEMI/HP2/ENG/TZ2/XX
(Question 10 continued)
(iii) Deduce the reagent(s) and catalyst needed to convert the product of the substitution
reaction to an amine.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (e)
1-bromopropane reacts with sodium hydroxide dissolved in hot ethanol when heated
under reflux. State an equation for the reaction.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3032
[2]
Please do not write on this page.
Answers written on this page
will not be marked.
3132
Please do not write on this page.
Answers written on this page
will not be marked.
3232
M12/4/CHEMI/HP2/ENG/TZ2/XX/M
MARKSCHEME
May 2012
CHEMISTRY
Higher Level
Paper 2
16 pages
–2–
M12/4/CHEMI/HP2/ENG/TZ2/XX/M
This markscheme is confidential and for the exclusive use of
examiners in this examination session.
It is the property of the International Baccalaureate and must not
be reproduced or distributed to any other person without the
authorization of IB Cardiff.
–3–
M12/4/CHEMI/HP2/ENG/TZ2/XX/M
General Marking Instructions
Assistant Examiners (AEs) will be contacted by their team leader (TL) through Scoris™, by e-mail
or telephone – if through Scoris™ or by e-mail, please reply to confirm that you have downloaded
the markscheme from IBIS. The purpose of this initial contact is to allow AEs to raise any queries
they have regarding the markscheme and its interpretation. AEs should contact their team leader
through Scoris™ or by e-mail at any time if they have any problems/queries regarding marking.
For any queries regarding the use of Scoris™, please contact emarking@ibo.org.
If you have any queries on administration please contact:
Rachel Bengough
Subject Operations
IB Assessment Centre
Peterson House
Malthouse Avenue
Cardiff Gate
Cardiff CF23 8GL
GREAT BRITAIN
Tel: +(44) 29 2054 7777
Fax: +(44) 29 2054 7778
E-mail: rachel.bengough@ibo.org
–4–
M12/4/CHEMI/HP2/ENG/TZ2/XX/M
1.
Follow the markscheme provided, award only whole marks and mark only in RED.
2.
Make sure that the question you are about to mark is highlighted in the mark panel on the right-hand
side of the screen.
3.
Where a mark is awarded, a tick/check () must be placed in the text at the precise point where it
becomes clear that the candidate deserves the mark. One tick to be shown for each mark awarded.
4.
Sometimes, careful consideration is required to decide whether or not to award a mark. In these
cases use Scoris™ annotations to support your decision. You are encouraged to write comments
where it helps clarity, especially for re-marking purposes. Use a text box for these additional
comments. It should be remembered that the script may be returned to the candidate.
5.
Personal codes/notations are unacceptable.
6.
Where an answer to a part question is worth no marks but the candidate has attempted the part
question, enter a zero in the mark panel on the right-hand side of the screen. Where an answer to a
part question is worth no marks because the candidate has not attempted the part question, enter an
“NR” in the mark panel on the right-hand side of the screen.
7.
If a candidate has attempted more than the required number of questions within a paper or section
of a paper, mark all the answers. Scoris™ will only award the highest mark or marks in line with
the rubric.
8.
Ensure that you have viewed every page including any additional sheets. Please ensure that you
stamp ‘seen’ on any page that contains no other annotation.
9.
Mark positively. Give candidates credit for what they have achieved and for what they have got
correct, rather than penalizing them for what they have got wrong. However, a mark should not be
awarded where there is contradiction within an answer. Make a comment to this effect using a text
box or the “CON” stamp.
–5–
M12/4/CHEMI/HP2/ENG/TZ2/XX/M
Subject Details: Chemistry HL Paper 2 Markscheme
Mark Allocation
Candidates are required to answer ALL questions in Section A [40 marks] and TWO questions in
Section B [2 x 25 marks]. Maximum total = [90 marks].
1.
A markscheme often has more marking points than the total allows. This is intentional.
2.
Each marking point has a separate line and the end is shown by means of a semicolon (;).
3.
An alternative answer or wording is indicated in the markscheme by a slash (/). Either wording can
be accepted.
4.
Words in brackets ( ) in the markscheme are not necessary to gain the mark.
5.
Words that are underlined are essential for the mark.
6.
The order of marking points does not have to be as in the markscheme, unless stated otherwise.
7.
If the candidate’s answer has the same “meaning” or can be clearly interpreted as being of
equivalent significance, detail and validity as that in the markscheme then award the mark.
Where this point is considered to be particularly relevant in a question it is emphasized by
OWTTE (or words to that effect).
8.
Remember that many candidates are writing in a second language. Effective communication is more
important than grammatical accuracy.
9.
Occasionally, a part of a question may require an answer that is required for subsequent
marking points. If an error is made in the first marking point then it should be penalized. However,
if the incorrect answer is used correctly in subsequent marking points then follow through marks
should be awarded. When marking, indicate this by adding ECF (error carried forward) on the
script.
10.
Do not penalize candidates for errors in units or significant figures, unless it is specifically referred
to in the markscheme.
11.
If a question specifically asks for the name of a substance, do not award a mark for a correct
formula unless directed otherwise in the markscheme, similarly, if the formula is specifically asked
for, unless directed otherwise in the markscheme do not award a mark for a correct name.
12.
If a question asks for an equation for a reaction, a balanced symbol equation is usually expected, do
not award a mark for a word equation or an unbalanced equation unless directed otherwise in the
markscheme.
13.
Ignore missing or incorrect state symbols in an equation unless directed otherwise in the
markscheme.
–6–
M12/4/CHEMI/HP2/ENG/TZ2/XX/M
SECTION A
1.
(a)
(b)
reaction is complete / all hydrogen peroxide/reactant is used up / no more bubbles
are being produced / layer of bubbles is constant / OWTTE;
correctly drawn tangent to the graph at 120 s;
rate = gradient of the tangent to the graph at 120 s / rate 
6.0  2.0
;
240  0
 0.017 mms1 ;
Accept answers in the range 0.014 to 0.020 mm s–1.
Units required for M3.
(c)
(i)
[3]
Species
Oxidation number of oxygen
H 2 O2
–1
H 2O
–2
O2
[1]
0
[2]
Award [2] for three correct.
Award [1] for two correct.
(ii)
Oxidation:
H2O2  O2  2H  2e ;
Reduction:
H2O2  2H  2e  2H2O ;
[2]
2.
(a)
(b)
–7–
M12/4/CHEMI/HP2/ENG/TZ2/XX/M
Mg (s)  2HCl(aq)  H2 (g)  MgCl2 (aq) ;
[1]
 0.0740 
3
n(Mg)  
  3.04 10 (mol) ;
 24.31 
Accept range 3.04  10 3 to 3.08  10 3 .
n(HCl)  (2.00 15.0 103 )  3.00 102 (mol) ;
Mg;
(c)
(i)
(ii)
(d)
n(H2 )  n(Mg)  3.04 103 (mol) ;
Accept same value as in 2(b).
Answer must be in range 3.04  10 3 to3.08  10 3 and must have 2, 3 or 4
significant figures.
3
6
 nRT  3.04 10  8.31 293 10
V 

;

P 
1.01105

 73.4 (cm3 ) ;
Accept answers in the range 72.3 to 74.3 (cm3).
gas leaks from apparatus / gas escapes;
the syringe stuck;
Mg impure;
[3]
[1]
[2]
[2 max]
–8–
3.
(a)
(b)
(c)
M12/4/CHEMI/HP2/ENG/TZ2/XX/M
radius of the metal/positive ion/cation increases;
attraction (between ions) is weaker;
[2]
higher charge (on cation);
smaller radius (of cation);
[2]
(i)
(ii)
(standard enthalpy of) atomization/∆Hϴatomization / (standard enthalpy of)
sublimation/∆Hϴsublimation;
lattice enthalpy  1049 kJ mol1
bond enthalpy F–F  158 kJ mol1
first ionization energy (Li)  520 kJ mol1
∆Hϴelectron affinity (F)  328 kJ mol1
∆Hϴatomization of Li  159 kJ mol1
[1]
(Data Booklet Table 13)
(Data Booklet Table 10)
(Data Booklet Table 7)
(Data Booklet Table 7)
(given)
∆Hfϴ = +159 + 1 (158) + 520 + (−328) − (1049);
2
1
 619 kJ mol ;
Accept use of theoretical value of lattice enthalpy, 1030 kJ mol 1 :
[2]
∆Hƒϴ = +159 + 1 (158) + 520 + (−328) − (1030)
2
 600 kJ mol
4.
Species
1
Lewis structure
Shape
Bond angle
XeF4
square planar;
90 ;
NO3
trigonal/triangular planar;
120 ;
[6]
Accept any combination of lines, dots or crosses to represent electron pairs.
–9–
5.
(a)
(i)
(ii)
(b)
6.
M12/4/CHEMI/HP2/ENG/TZ2/XX/M
atoms which have same atomic number but different mass number / atoms
of the same element which have different numbers of neutrons / atoms with
the same number of protons but different numbers of neutrons / atom of an
element with a fixed number of protons but a number of neutrons which can
be variable;
medical tracer / used to investigate functioning of thyroid gland / to treat
thyroid cancer / to treat hyperthyroidism;
produces gamma rays/ionizing radiation / destroys healthy cells / OWTTE;
Do not accept I-131 is radioactive.
living organisms have 12C:14C ratio constant/same as atmosphere / OWTTE;
after death no more 14C is absorbed and 14C level drops / 12C:14C ratio changes
with time / 14C decays / remains become less radioactive;
rate of decay of 14C is constant / half-life of 14C is known;
measuring radioactivity indicates length of time since death / OWTTE;
[1]
[2]
[3 max]
Cr( NO3 )3 :
acidic;
high charge density of small Cr 3 causes it to be a Lewis acid /
[Cr(H2O)6 ]3
[Cr(OH)(H2O)5 ]2  H  / OWTTE;
CH 3COONH 4 :
(approximately) neutral;
salt of a weak acid and weak base / K a of NH 4  is approximately equal to K b of
CH3COO / ions are a weak acid and a weak base / OWTTE;
[4]
– 10 –
M12/4/CHEMI/HP2/ENG/TZ2/XX/M
SECTION B
7.
(a)
(i)
Empirical formula:
simplest (whole number) ratio of atoms/moles of each element present in a
compound/molecule;
Molecular formula:
actual numbers of atoms/moles of each element present
compound/molecule / whole number multiple of empirical formula;
in a
[2]
n(C)  4.54 (mol), n(H)  9.11(mol) and n(O)  2.27 (mol) ;
C2 H 4 O ;
Accept other valid method for calculation.
[2]
(iii)
C 4 H8 O 2 ;
[1]
(iv)
CH3CH2CH2COOH ;
Accept full or condensed structural formulas.
[1]
(v)
CH3CH2COOCH3 / CH3COOCH2CH3 / HCOOCH2CH 2 CH3 / HCOOCH(CH3 )2 ;
Accept full or condensed structural formulas.
[1]
(ii)
(vi) Stronger bond:
C=O /double bond;
Longer bond:
C–O /single bond;
(vii) bond length and bond strength identical for both carbon to oxygen bonds;
intermediate between single and double bond length and strength;
due to delocalization of the electrons (in the p orbitals);
Accept use of Data Booklet values of bond lengths and bond enthalpies.
Accept diagram of delocalization or the two resonance structures for M3.
[2]
[3]
– 11 –
(b)
(i)
(ii)
M12/4/CHEMI/HP2/ENG/TZ2/XX/M
mixing/joining together/combining/merging of (atomic) orbitals to form
molecular/new orbitals (of equal energy);
sp3 ;
isolated C atom electron configuration 1s2 2s2 2p2 / excited state C electron
configuration is 1s2 2s12p3;
2s1 2p3 electrons blend to form four identical hybrid orbitals;
hybrid orbitals lower in total energy than atomic orbitals;
repulsion of (identical hybrid) orbitals creates a tetrahedral shape;
Accept suitably annotated diagram for M2, M3 and M4.
[1]
[3 max]
(iii) diamond:
sp3 ;
graphite:
sp 2 ;
(p) electrons delocalized (around layer);
(c)
(i)
Al2Cl6 :
covalent bonding / dimer/molecular structure;
no free charges when molten so not an electrical conductor;
Al2O3 :
ionic / lattice structure;
ions free to move/mobile in molten state;
(ii)
[3]
vigorous reaction / fizzing / fumes are seen / heat is released / OWTTE;
HCl (g) evolved;
Al2O3/Al(OH)3 is formed;
Accept suitable equation for second and third marking points.
[4]
[2 max]
– 12 –
8.
(a)
(i)
M12/4/CHEMI/HP2/ENG/TZ2/XX/M
enthalpy on y-axis;
Do not accept energy.
reactants higher than products;
H labelled;
[3]
reactants
enthalpy
H
products
Accept appropriate formulas for reactants and products.
Arrow heads not needed.
57.6 is acceptable as an alternative to H .
(ii)
(iii)
(b)
(c)
products are more stable as they are at a lower enthalpy level / energy has
been given off by the reactants / reaction is exothermic / OWTTE;
[1]
n(NaOH)  0.125 mol ;
change in heat energy = (–57.6  0.125) = –7.20 (kJ) / heat released
 (57.6  0.125)  7.20 (kJ) ;
[2]
more vigorous reaction / more gas bubbles / OWTTE;
more heat released;
solid decreases more quickly;
q  (mcT )100.0  4.18  3.50 /1463 J /1460 J;
5.35
n(NH 4Cl) 
/ 0.100 mol ;
53.5
∆H = +14.6 / 14.6 (kJ mol−1);
Accept q  105.35  4.18  3.50 / 1541 J .
Accept ∆H = +15.4 / 15.4 (kJ mol−1).
[1 max]
[3]
– 13 –
(d)
[OH ] 

M12/4/CHEMI/HP2/ENG/TZ2/XX/M

0.500 1.78 105  2.98 103 mol dm3 ;
 1.00 1014 
pOH   log10 [OH ]  2.526 / [H  ]  
 3.35 1012 mol dm 3 ;
3 
 2.98 10 
pH  11.47 ;
Accept correct answer obtained using another method.
Assumption:
[NH3 ]  0.500 moldm3 / [NH4 ]  [OH ] / all OH  ions come from the reaction
of ammonia with water and not from the dissociation of water / temperature is 25
C/298 K / OWTTE;
(e)
(i)
(ii)
(iii)
resists change in pH when small amounts of a strong base/strong acid/water
are added to it;
(f)
[1]
[NH3 ]  0.250 moldm3 ;
[NH4 ]  0.250 mol dm3 ;
[2]
pOH  pKb  4.75 ;
pH  9.25 ;
[2]
(iv) equilibrium shifted left in buffer / OWTTE;
(v)
[4]
[1]
acid neutralized by hydroxide / most of the added H  ions react with NH3 ;
more ammonia reacts with water to replace hydroxide ions / more NH 4 
ions form so there is little change in the pH / OWTTE;
Accept equations.
[2]
(i)
colours of HIn and In– are different / OWTTE;
[1]
(ii)
colour change occurs when [HIn]  [In  ] ;
pH  pKa ;
OR
pH range is a range of pH values either side of pKa value;
lower pH when acid colour is seen and upper pH when alkaline colour seen;
[2]
– 14 –
9.
(a)
(b)
M12/4/CHEMI/HP2/ENG/TZ2/XX/M
(i)
1s2 2s2 2p6 3s2 3p6 3d6 4s2 / 1s2 2s2 2p6 3s2 3p6 4s2 3d6 ;
[1]
(ii)
[Ar] 3d5 ;
[1]
(iii) lone pair of electrons (on C);
CN  acts as a Lewis base / Fe3 acts as a Lewis acid;
dative covalent/coordinate bond formed (between CN  and Fe3 );
ligands occupy an octahedral shape around central metal ion / coordination
number of Fe3 is 6;
[4]
(iv) d sub-level splits (into two sets of orbitals of different energy) / –– –– –
colour due to electron transitions between (split) d orbitals;
[2]
E;
(i)
2SO2 (g)  O2 (g)  2SO3 (g) ;
[1]
(ii)
Pt/platinum / V2O5 /vanadium(V) oxide/vanadium pentoxide;
[1]
(iii) provides a reaction pathway with lower activation energy;
more molecules/particles have sufficient energy to react;
(iv) reduces energy costs (as reaction occurs at lower temperatures) / OWTTE;
catalyst can be reused;
increases reaction rate so more product produced in a given time / OWTTE;
(v)
entropy decreases;
products have fewer moles of gas than reactants;
(vi) less spontaneous at higher temperatures;
spontaneous when G  0 / G  H  T S ;
T S always positive so spontaneous when T S  H / OWTTE;
(c)
(i)
(ii)
[2]
[2 max]
[2]
[3]
k:
rate constant;
A:
Arrhenius constant / frequency/pre-exponential factor;
[2]
 Ea
/ Ea = –gradient  R;
R
  (16)  8.31  133 (kJ mol1 ) /1.33 105 (J mol1 ) ;
[2]
gradient 
(iii) ln A  (intercept on y-axis )23.2 ;
A  1.190 1010 ;
[2]
– 15 –
10.
(a)
(i)
(ii)
M12/4/CHEMI/HP2/ENG/TZ2/XX/M
ethanol and methanoic acid/methanoic anhydride/methanoyl chloride;
H2SO4 /H and heat;
N
(CH2)6
N
C
(CH2)4
[2]
C
H
H
O
O
Award [1] for the correct amide link.
Award [1] if the rest of the structure is correct.
(b)
nylon fabric / clothing / ropes;
[3]
(i)
(concentrated) sulfuric acid/ H 2SO4 / phosphoric acid/ H3PO4 ;
Acid must be named or formula given.
[1]
(ii)
step I:
HBr/hydrogen bromide;
gaseous / anhydrous / inert/non-polar solvent;
step II:
sodium hydroxide/NaOH / potassium hydroxide/KOH;
aqueous (solution) / dilute / warm / heat / reflux;
(iii) slower rate because carbon to chlorine bond stronger than carbon to bromine
bond / OWTTE;
(c)
(i)
(ii)
compounds with the same molecular formula but different arrangements of
atoms / compounds with the same molecular formula but different structural
formulas;
[4]
[1]
[1]
CH3CH(Br)CH2CH3 ;
secondary/ 2 ;
CH2 (Br)CH(CH3 )CH3 ;
primary/ 1 ;
Accept full or condensed structural formulas.
[4]
– 16 –
(d)
(i)
M12/4/CHEMI/HP2/ENG/TZ2/XX/M
C has partial positive charge / C to Br bond is polar;
[1]
(ii)
curly arrow going from lone pair/negative charge on C in CN  to C;
Do not allow curly arrow originating on N in CN  .
curly arrow showing Br leaving;
Allow curly arrow going from bond between C and Br to Br in reactant or
transition state.
representation of transition state showing negative charge, square brackets
and partial bonds;
Do not penalize if NC and Br are not at 180 to each other.
Do not award M3 if CN–C bond is represented.
formation of organic product and Br–;
(e)
[4]
(iii) hydrogen/H2;
(catalyst) nickel/Ni / palladium/Pd / platinum/Pt;
[2]
CH3CH2CH2 Br  OH 
 CH3CH= CH2  H2O  Br 
correct organic product;
products of H 2O and Br  ;
[2]
N12/4/CHEMI/HPM/ENG/TZ0/XX
88126101
CHEMISTRY
Higher level
Paper 1
Friday 9 November 2012 (afternoon)
1 hour
INSTRUCTIONS TO CANDIDATES
• Do not open this examination paper until instructed to do so.
• Answer all the questions.
• For each question, choose the answer you consider to be the best and indicate your choice on
the answer sheet provided.
• The periodic table is provided for reference on page 2 of this examination paper.
• The maximum mark for this examination paper is [40 marks].
8812-6101
17 pages
© International Baccalaureate Organization 2012
8812-6101
23
V
50.94
87
Fr
(223)
88
Ra
(226)
‡
†
89 ‡
Ac
(227)
90
Th
232.04
58
Ce
140.12
91
Pa
231.04
59
Pr
140.91
73
Ta
180.95
38
Sr
87.62
37
Rb
85.47
22
Ti
47.90
56
57 †
72
55
Ba
La
Cs
Hf
132.91 137.34 138.91 178.49
20
Ca
40.08
19
K
39.10
41
Nb
92.91
39
Y
88.91
12
Mg
24.31
11
Na
22.99
92
U
238.03
60
Nd
144.24
74
W
183.85
42
Mo
95.94
24
Cr
52.00
Relative atomic mass
Element
Atomic number
40
Zr
91.22
21
Sc
44.96
4
Be
9.01
2
3
Li
6.94
1
H
1.01
1
30
Zn
65.37
93
Np
(237)
94
Pu
(242)
95
Am
(243)
96
Cm
(247)
97
Bk
(247)
98
Cf
(251)
61
66
62
63
64
65
Pm
Dy
Sm
Tb
Eu
Gd
146.92 150.35 151.96 157.25 158.92 162.50
75
80
76
77
78
79
Re
Os
Pt
Au
Hg
Ir
186.21 190.21 192.22 195.09 196.97 200.59
48
44
45
46
47
Cd
Ru
Rh
Pd
Ag
101.07 102.91 106.42 107.87 112.40
29
Cu
63.55
43
Tc
98.91
28
Ni
58.71
26
Fe
55.85
25
Mn
54.94
27
Co
58.93
The Periodic Table
50
Sn
118.69
32
Ge
72.59
14
Si
28.09
6
C
12.01
4
99
Es
(254)
100
Fm
(257)
67
68
Ho
Er
164.93 167.26
81
82
Tl
Pb
204.37 207.19
49
In
114.82
31
Ga
69.72
13
Al
26.98
5
B
10.81
3
101
Md
(258)
69
Tm
168.93
83
Bi
208.98
51
Sb
121.75
33
As
74.92
15
P
30.97
7
N
14.01
5
35
Br
79.90
17
Cl
35.45
9
F
19.00
7
85
At
(210)
102
No
(259)
103
Lr
(260)
70
71
Lu
Yb
173.04 174.97
84
Po
(210)
52
53
Te
I
127.60 126.90
34
Se
78.96
16
S
32.06
8
O
16.00
6
86
Rn
(222)
54
Xe
131.30
36
Kr
83.80
18
Ar
39.95
10
Ne
20.18
2
He
4.00
0
–2–
N12/4/CHEMI/HPM/ENG/TZ0/XX
–3–
1.
2.
N12/4/CHEMI/HPM/ENG/TZ0/XX
What is the number of ions in 0.20 mol of (NH4)3PO4?
A.
8.0 × 10−1
B.
1.2 × 1023
C.
4.8 × 1023
D.
2.4 × 1024
The equation for the reduction of iron(III) oxide is:
Fe 2 O3 (s) + 3CO (g) → 2Fe (s) + 3CO 2 (g)
What mass of carbon dioxide, in g, is produced by the complete reduction of 80 g of iron(III) oxide?
3.
A.
44
B.
66
C.
88
D.
132
3.0 dm3 of ethyne, C2H2 , is mixed with 3.0 dm3 of hydrogen and ignited. The equation for the reaction
that occurs is shown below.
C2 H 2 (g) + 2H 2 (g) → C2 H 6 (g)
Assuming the reaction goes to completion and all gas volumes are measured at the same temperature
and pressure, what volume of ethane, C2H6 , in dm3, is formed?
A.
1.5
B.
2.0
C.
3.0
D.
6.0
8812-6101
Turn over
–4–
4.
5.
N12/4/CHEMI/HPM/ENG/TZ0/XX
Which ion would be deflected the most in a mass spectrometer?
A.
35
Cl+ (g)
B.
37
C.
35
D.
37
Cl+ (g)
Cl2+ (g)
Cl2+ (g)
Which of the graphs below shows the successive logarithmic ionization energies of phosphorus?
Log ionization energy / kJ mol–1
B.
Log ionization energy / kJ mol–1
A.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Number of electrons removed
Log ionization energy / kJ mol–1
D.
Log ionization energy / kJ mol–1
C.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Number of electrons removed
8812-6101
Number of electrons removed
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Number of electrons removed
–5–
6.
7.
8.
N12/4/CHEMI/HPM/ENG/TZ0/XX
Which combination is correct for the properties of the alkali metals from Li to Cs?
Atomic radius
Melting point
First ionization
energy
A.
increases
increases
increases
B.
increases
decreases
decreases
C.
increases
increases
decreases
D.
decreases
decreases
increases
Which equation represents a reaction that occurs under normal conditions?
A.
2LiBr (aq) + I 2 (aq) → 2LiI (aq) + Br2 (aq)
B.
2KF (aq) + Cl2 (aq) → 2KCl (aq) + F2 (aq)
C.
2LiCl (aq) + I 2 (aq) → 2LiI (aq) + Cl2 (aq)
D.
2KBr (aq) + Cl2 (aq) → 2KCl (aq) + Br2 (aq)
Which combination of statements about the oxides of period 3 elements is correct?
State at room temperature
Electrical conductivity in molten state
Na2O
Al2O3
P4O10
Na2O
Al2O3
P4O10
A.
solid
solid
gas
good
good
good
B.
solid
solid
solid
good
good
poor
C.
solid
liquid
liquid
good
poor
poor
D.
solid
solid
solid
poor
poor
good
8812-6101
Turn over
–6–
9.
10.
Which is an ionic compound?
A.
Mg3N2
B.
Al2Cl6
C.
SiO2
D.
SF6
Which molecule is polar?
Molecule
11.
Shape
A.
CO2
linear
B.
SO3
trigonal planar
C.
CCl4
tetrahedral
D.
SO2
bent (V-shaped)
Which intermolecular forces are present in HI (l)?
I.
Hydrogen bonding
II.
Dipole-dipole forces
III.
Van der Waals’ (London dispersion) forces
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
8812-6101
N12/4/CHEMI/HPM/ENG/TZ0/XX
–7–
12.
In the molecule SF4 , which are the correct bond angles?
F
β
F
α/
13.
14.
N12/4/CHEMI/HPM/ENG/TZ0/XX
β/
F
S
α
F
A.
180
120
B.
187
103
C.
187
120
D.
180
90
Which substances have delocalized electrons in their structure?
I.
Ethanal
II.
Ozone
III.
Benzene
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
A 5.00 g sample of a substance was heated from 25.0 °C to 35.0 °C using 2.00 × 102 J of energy.
What is the specific heat capacity of the substance in J g–1 K–1?
A.
4.00 × 10−3
B.
2.50 × 10−1
C.
2.00
D.
4.00
8812-6101
Turn over
–8–
15.
N12/4/CHEMI/HPM/ENG/TZ0/XX
Using the equations below:
C (s) + O 2 (g) → CO 2 (g)
∆H Ö = −390 kJ
H 2 (g) + 12 O 2 (g) → H 2 O (l)
∆H Ö = −286 kJ
CH 4 (g) + 2O 2 (g) → CO 2 (g) + 2H 2 O (l)
∆H Ö = −890 kJ
what is ∆H Ö , in kJ, for the following reaction?
C (s) + 2H 2 (g) → CH 4 (g)
16.
17.
A.
–214
B.
–72
C.
+72
D.
+214
Which is the best definition of electron affinity?
A.
The ability of an atom to attract the electrons in a covalent bond.
B.
The attraction of an atom for an electron.
C.
The enthalpy change when an atom gains an electron.
D.
The enthalpy change when a gaseous atom gains an electron.
Which is the best definition of the standard state?
A.
The standard state of a solid is the most pure form of the solid.
B.
The standard state of a solid is the most pure form of the solid at 298 °C .
C.
The standard state of a gas is the most pure form of the gas at 298 °C .
D.
The standard state of a gas is the most pure form of the gas at a pressure of 100 kPa.
8812-6101
–9–
18.
N12/4/CHEMI/HPM/ENG/TZ0/XX
Consider the following information:
CaCO3 (s) → CaO (s) + CO 2 (g)
∆H = +179 kJ mol−1
∆S = +161.0 J K −1 mol −1
What happens to the spontaneity of this reaction as the temperature is increased?
19.
A.
The reaction becomes more spontaneous as the temperature is increased.
B.
The reaction becomes less spontaneous as the temperature is increased.
C.
The reaction remains spontaneous at all temperatures.
D.
The reaction remains non-spontaneous at all temperatures.
Which piece of equipment could not be used in an experiment to measure the rate of this reaction?
CH 3COCH 3 (aq) + I 2 (aq) → CH 3COCH 2 I (aq) + H + (aq) + I − (aq)
A.
A colorimeter
B.
A gas syringe
C.
A stopwatch
D.
A pH meter
8812-6101
Turn over
– 10 –
20.
N12/4/CHEMI/HPM/ENG/TZ0/XX
Which graph would be produced by a 2nd order reaction if the rate equation is rate = k [X]2 ?
[X] / mol dm–3
B.
[X] / mol dm–3
A.
Time (s)
Rate / mol dm–3 s–1
D.
Rate / mol dm–3 s–1
C.
Time (s)
[X] / mol dm–3
21.
[X] / mol dm–3
Which step in a multi-step reaction mechanism will be rate-determining?
A.
The first step
B.
The last step
C.
The step with the highest activation energy
D.
The step with the lowest activation energy
8812-6101
– 11 –
22.
Iron(III) ions, Fe3+, react with thiocyanate ions, SCN–, in a reversible reaction to form a red solution.
Which changes to the equilibrium will make the solution go red?
Fe3+ (aq) + SCN − (aq) [FeSCN]2+ (aq)
Yellow
23.
N12/4/CHEMI/HPM/ENG/TZ0/XX
I.
Increasing the temperature
II.
Adding FeCl3
III.
Adding a catalyst
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
∆H Ö = + ve
Red
Consider the following reversible reaction:
2NO 2 (g) N 2 O 4 (g)
What is the value of Kc for the reaction when the equilibrium concentrations are [NO 2 ] = 4.0 mol dm −3
and [N 2 O 4 ] = 4.0 mol dm −3 ?
24.
A.
0.25
B.
0.50
C.
2.0
D.
4.0
Which substance can act as a Lewis acid but not as a Brønsted–Lowry acid?
A.
HCl
B.
CH3COOH
C.
BF3
D.
CF3COOH
8812-6101
Turn over
– 12 –
25.
26.
27.
N12/4/CHEMI/HPM/ENG/TZ0/XX
Which row correctly describes 1.0 mol dm–3 NaOH (aq)?
pH
Colour in universal
indicator solution
Electrical
conductivity
A.
14
purple
good
B.
10
green
poor
C.
14
red
good
D.
10
blue
poor
For pure water at 50 °C , Kw = 5.48 × 10−14 . What is the pH of this water?
A.
4.8
B.
6.6
C.
7.0
D.
8.2
Which is the strongest acid?
Acid
pKa
A.
chloroethanoic
2.87
B.
iodoethanoic
3.18
C.
benzoic
4.20
D.
pentanoic
4.83
8812-6101
– 13 –
28.
29.
Which salts will dissolve in water to give solutions with a pH above 7?
I.
Na2CO3
II.
CH3COONa
III.
Na2SO4
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
During a titration, 0.1 mol dm–3 sodium hydroxide is added to 0.1 mol dm–3 ethanoic acid. Which
indicator would be the best to use as an end point indicator in this titration?
Indicator
30.
N12/4/CHEMI/HPM/ENG/TZ0/XX
pH range of indicator
A.
methyl orange
3.2– 4.4
B.
bromophenol blue
3.0 – 4.6
C.
bromothymol blue
6.0 –7.6
D.
phenolphthalein
8.2–10.0
What is the correct systematic name of MnO2?
A.
Manganese(II) oxide
B.
Manganese(IV) oxide
C.
Magnesium(II) oxide
D.
Magnesium(IV) oxide
8812-6101
Turn over
– 14 –
31.
N12/4/CHEMI/HPM/ENG/TZ0/XX
A voltaic cell is made by connecting zinc and lead half-cells. The overall equation for the reaction
occurring in the cell is shown below.
Zn (s) + Pb 2+ (aq) → Pb (s) + Zn 2+ (aq)
Which statements are correct when the cell produces electricity?
32.
I.
The zinc is oxidized.
II.
Electrons move from zinc to lead in the external circuit.
III.
The mass of the lead electrode increases.
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
Consider the following standard electrode potential values:
Fe3+ (aq) + e − Fe 2+ (aq)
E Ö = + 0.77 V
MnO 4 − (aq) + 8H + (aq) + 5e − Mn 2+ (aq) + 4H 2O (l)
E Ö = +1.51 V
What is the cell potential, in V, for this reaction?
MnO 4 − (aq) + 8H + (aq) + 5Fe 2+ (aq) → Mn 2+ (aq) + 4H 2 O (l) + 5Fe3+ (aq)
A.
–2.28
B.
– 0.74
C.
+ 0.74
D.
+2.28
8812-6101
– 15 –
33.
N12/4/CHEMI/HPM/ENG/TZ0/XX
Consider the following standard electrode potential values:
Ca 2+ (aq) + 2e − Ca (s)
E Ö = −2.87 V
Fe 2+ (aq) + 2e − Fe (s)
E Ö = −0.45 V
Ni 2+ (aq) + 2e − Ni (s)
E Ö = −0.26 V
Fe3+ (aq) + e − Fe 2+ (aq)
E Ö = +0.77 V
Which reaction is spontaneous?
34.
35.
A.
Ca 2+ (aq) + Ni (s) → Ca (s) + Ni 2+ (aq)
B.
3Fe 2+ (aq) → Fe (s) + 2Fe3+ (aq)
C.
Fe (s) + 2Fe3+ (aq) → 3Fe 2+ (aq)
D.
Fe 2+ (aq) + Ni (s) → Fe (s) + Ni 2+ (aq)
Which compound has the lowest boiling point?
A.
(CH3)3COH
B.
CH3(CH2)3OH
C.
(CH3)4C
D.
CH3(CH2)3CH3
Which compound would decolourize bromine water in the dark?
A.
CH3COCH2CH3
B.
CH3(CH2)4OH
C.
CH3CHCHCH3
D.
CH3(CH2)3CH3
8812-6101
Turn over
– 16 –
36.
37.
38.
N12/4/CHEMI/HPM/ENG/TZ0/XX
Which statement about the oxidation of alcohols is correct?
A.
Oxidation of propan-1-ol produces propanone.
B.
Mild oxidation of butan-1-ol produces butanal.
C.
Strong oxidation of pentan-2-ol produces pentanoic acid.
D.
Mild oxidation of butan-2-ol produces butanal.
Which halogenoalkane will react most quickly with sodium hydroxide?
A.
CH3CH2CH2CH2Cl
B.
CH3CH2CH2CH2Br
C.
(CH3)3CCl
D.
(CH3)3CBr
Which would be the main product of the reaction between 1-bromobutane and concentrated sodium
hydroxide in hot ethanol?
A.
CH2CHCH2CH3
B.
CH3CHCHCH3
C.
CH3CH2CH2CH3
D.
CH3CHOHCH2CH3
8812-6101
– 17 –
39.
40.
N12/4/CHEMI/HPM/ENG/TZ0/XX
Which molecules can react to form a condensation polymer with a dicarboxylic acid such as
hexanedioic acid?
I.
HOCH2CH2OH
II.
CH3CH2NH2
III.
H2N(CH2)6NH2
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
50 cm3 of copper(II) sulfate solution is measured into a plastic cup using a 100 cm3 measuring
cylinder. Excess zinc powder is added and the temperature rise that occurs is measured
with a –10 °C to +110 °C thermometer. The enthalpy change for the reaction is then calculated. Which statement is correct?
A.
Systematic error will be reduced by repeating the experiment several times and averaging
the results.
B.
Random error will be reduced by insulating the plastic cup.
C.
Random error will be reduced by using a 50 cm3 graduated pipette instead of a measuring
cylinder.
D.
Systematic error will be increased by using a larger volume of copper(II) sulfate solution.
8812-6101
N12/4/CHEMI/HPM/ENG/TZ0/XX/M
MARKSCHEME
November 2012
CHEMISTRY
Higher Level
Paper 1
2 pages
–2–
N12/4/CHEMI/HPM/ENG/TZ0/XX/M
1.
C
16.
D
31.
D
46.
–
2.
B
17.
D
32.
C
47.
–
3.
A
18.
A
33.
C
48.
–
4.
C
19.
B
34.
C
49.
–
5.
A
20.
D
35.
C
50.
–
6.
B
21.
C
36.
B
51.
–
7.
D
22.
A
37.
D
52.
–
8.
B
23.
A
38.
A
53.
–
9.
A
24.
C
39.
B
54.
–
10.
D
25.
A
40.
C
55.
–
11.
C
26.
B
41.
–
56.
–
12.
B
27.
A
42.
–
57.
–
13.
C
28.
A
43.
–
58.
–
14.
D
29.
D
44.
–
59.
–
15.
B
30.
B
45.
–
60.
–
N12/4/CHEMI/HP2/ENG/TZ0/XX
88126102
CHEMISTRY
HIGHER level
Paper 2
Candidate session number
0
0
Examination code
Friday 9 November 2012 (afternoon)
8
2 hours 15 minutes
8
1
2
–
6
1
0
2
INSTRUCTIONS TO CANDIDATES
•
•
•
•
•
•
•
•
Write your session number in the boxes above.
Do not open this examination paper until instructed to do so.
Section A: answer all questions.
Section B:answer two questions.
Write your answers in the boxes provided.
A calculator is required for this paper.
A clean copy of the Chemistry Data Booklet is required for this paper.
The maximum mark for this examination paper is [90 marks].
32 pages
© International Baccalaureate Organization 2012
0132
–2–
N12/4/CHEMI/HP2/ENG/TZ0/XX
Section a
Answer all questions. Write your answers in the boxes provided.
1.
Two groups of students (Group A and Group B) carried out a project* on the chemistry of some
group 7 elements (the halogens) and their compounds.
(a)
In the first part of the project, the two groups had a sample of iodine monochloride
(a corrosive brown liquid) prepared for them by their teacher using the following reaction.
I 2 (s) + Cl2 (g) → 2ICl (l)
The following data were recorded.
Mass of I2 (s)
(i)
(ii)
10.00 g
Mass of Cl2 (g)
2.24 g
Mass of ICl (l) obtained
8.60 g
State the number of significant figures for the masses of I2 (s) and ICl (l).
I2 (s):
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ICl (l):
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The iodine used in the reaction was in excess. Determine the theoretical yield, in g,
of ICl (l).
[1]
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
*
Adapted from J Derek Woollins, (2009), Inorganic Experiments and Open University, (2008), Exploring the Molecular World.
0232
–3–
N12/4/CHEMI/HP2/ENG/TZ0/XX
(Question 1 continued)
[1]
(iii) Calculate the percentage yield of ICl (l).
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv) Using a digital thermometer, the students discovered that the reaction was
exothermic. State the sign of the enthalpy change of the reaction, ∆H .
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
Although the molar masses of ICl and Br2 are very similar, the boiling point of ICl is
97.4 °C and that of Br2 is 58.8 °C. Explain the difference in these boiling points in terms
of the intermolecular forces present in each liquid.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
0332
–4–
N12/4/CHEMI/HP2/ENG/TZ0/XX
(Question 1 continued)
(c)
The students reacted ICl (l) with CsBr (s) to form a yellow solid, CsICl2 (s), as one of
the products. CsICl2 (s) has been found to produce very pure CsCl (s) which is used in
cancer treatment.
To confirm the composition of the yellow solid, Group A determined the amount of iodine
in 0.2015 g of CsICl2 (s) by titrating it with 0.0500 mol dm–3 Na2S2O3 (aq). The following
data were recorded for the titration.
Mass of CsICl2 (s) taken
(in g ± 0.0001)
(i)
0.2015
Initial burette reading of
0.0500 mol dm–3 Na2S2O3 (aq)
(in cm3 ± 0.05)
1.05
Final burette reading of
0.0500 mol dm–3 Na2S2O3 (aq)
(in cm3 ± 0.05)
25.25
Calculate the percentage of iodine by mass in CsICl2 (s), correct to three
significant figures.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
State the volume, in cm3, of 0.0500 mol dm–3 Na2S2O3 (aq) used in the titration.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
0432
–5–
N12/4/CHEMI/HP2/ENG/TZ0/XX
(Question 1 continued)
(iii) Determine the amount, in mol, of 0.0500 mol dm–3 Na2S2O3 (aq) added in the titration.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv) The overall reaction taking place during the titration is:
CsICl2 (s) + 2Na 2S2 O3 (aq) → NaCl (aq) + Na 2S4 O6 (aq) + CsCl (aq) + NaI (aq)
Calculate the amount, in mol, of iodine atoms, I, present in the sample of CsICl2 (s).
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (v)
[1]
Calculate the mass of iodine, in g, present in the sample of CsICl2 (s).
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (vi) Determine the percentage by mass of iodine in the sample of CsICl2 (s), correct to
three significant figures, using your answer from (v).
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
0532
–6–
N12/4/CHEMI/HP2/ENG/TZ0/XX
(Question 1 continued)
(d)
Group B heated the yellow solid, CsICl2 (s), which turned white and released a brown gas
which condensed into a brown liquid.
Group B identified the white solid as CsCl (s). Suggest the identity of the brown liquid.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (e)
When iodine reacts with excess chlorine, ICl3 can form. Deduce the Lewis (electron dot)
structure of ICl3 and ICl2– and state the name of the shape of each species.
ICl3
[4]
ICl2–
Lewis structure
Name of shape
(This question continues on the following page)
0632
–7–
N12/4/CHEMI/HP2/ENG/TZ0/XX
(Question 1 continued)
(f)
In this project the students explored several aspects of the chemistry of the halogens. In the original preparation of ICl (l), they observed the yellow-green colour of
chlorine gas, Cl2 (g), reacting with solid iodine, I2 (s).
(i)
[1]
State the full electron configuration of iodine ( Z = 53).
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Chlorine can also react with water. State the balanced chemical equation for the
reaction of Cl2 (g) with water.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) One important use of chlorine is in the synthesis of poly(chloroethene), PVC.
Identify the monomer used to make PVC and state one of the uses of PVC.
[2]
Monomer:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Use:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
0732
–8–
2.
N12/4/CHEMI/HP2/ENG/TZ0/XX
Lithium and boron are elements in period 2 of the periodic table. Lithium occurs in group 1
(the alkali metals) and boron occurs in group 3. Isotopes exist for both elements.
(a)
(i)
Distinguish between the terms group and period.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Lithium exists as two isotopes with mass numbers of 6 and 7. Deduce the number
of protons, electrons and neutrons for each isotope.
Mass number
(A)
Number of
protons
Number of
electrons
[2]
Number of
neutrons
6
7
(iii) The electron configuration of boron is 1s2 2s2 2p1. Draw the shape of an s orbital
and a px orbital on the axes below.
y
[1]
y
x
z
x
z
s orbital
px orbital
(This question continues on the following page)
0832
–9–
N12/4/CHEMI/HP2/ENG/TZ0/XX
(Question 2 continued)
(b)
(i)
Explain why metals are good conductors of electricity and why they are malleable.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Cobalt is a transition metal. One common ion of cobalt is Co3+. Draw the orbital
diagram (using the arrow-in-box notation) for the Co3+ ion.
1s
2s
2p
3s
3p
4s
[1]
3d
[1]
(iii) State the other most common ion of cobalt.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [3]
(iv) Explain why the complex [Co(NH3)6]Cl3 is coloured.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
0932
– 10 –
Please do not write on this page.
Answers written on this page
will not be marked.
1032
N12/4/CHEMI/HP2/ENG/TZ0/XX
– 11 –
3.
N12/4/CHEMI/HP2/ENG/TZ0/XX
Buffer solutions are widely used in both chemical and biochemical systems.
(a)
[1]
Describe the composition of an acidic buffer solution.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
Determine the pH of a buffer solution, correct to two decimal places, showing your
working, consisting of 10.0 g of CH3COOH and 10.0 g of CH3COONa in 0.250 dm3
of solution. Ka for CH 3COOH = 1.8 × 10−5 at 298 K.
[5]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
1132
– 12 –
N12/4/CHEMI/HP2/ENG/TZ0/XX
Section b
Answer two questions. Write your answers in the boxes provided.
4.
Arsenic and nitrogen play a significant role in environmental chemistry. Arsenous acid,
H3AsO3, can be found in oxygen-poor (anaerobic) water, and nitrogen-containing fertilizers
can contaminate water.
(a)
(i)
Define oxidation and reduction in terms of electron loss or gain.
[1]
Oxidation:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reduction:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Deduce the oxidation numbers of arsenic and nitrogen in each of the following
species.
As2O3:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . NO3–:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [4]
H3AsO3: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . N2O3:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) Distinguish between the terms oxidizing agent and reducing agent.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
1232
– 13 –
N12/4/CHEMI/HP2/ENG/TZ0/XX
(Question 4 continued)
(iv) In the removal of arsenic from contaminated groundwater, H3AsO3 is often first
oxidized to arsenic acid, H3AsO4.
The following unbalanced redox reaction shows another method of forming H3AsO4.
As 2 O3 (s) + NO3− (aq) → H 3 AsO 4 (aq) + N 2 O3 (aq)
Deduce the balanced redox equation in acid, and then identify both the oxidizing
and reducing agents.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
The electrolysis of aqueous copper(II) sulfate is an example of an electrolysis process
where the nature of the electrodes can determine which products form. Platinum electrodes
were used in process 1 and copper electrodes in process 2.
(i)
Draw an annotated diagram of the electrolytic cell in process 1 and identify the
direction of electron flow.
[2]
(This question continues on the following page)
Turn over
1332
– 14 –
N12/4/CHEMI/HP2/ENG/TZ0/XX
(Question 4 continued)
(ii)
For process 1 (platinum electrodes), state the half-equations occurring at the
positive electrode (anode) and negative electrode (cathode). Include state symbols
for all species. Describe what is observed at each electrode and comment on any
change in the colour and the acidity of the solution.
[7]
Half-equation at positive electrode (anode):
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Half-equation at negative electrode (cathode):
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Observation at positive electrode (anode):
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Observation at negative electrode (cathode):
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Change in colour (if any) of the solution:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Change in acidity (if any) of the solution:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
1432
– 15 –
N12/4/CHEMI/HP2/ENG/TZ0/XX
(Question 4 continued)
(iii) For process 2 (copper electrodes), state the half-equations occurring at the
positive electrode (anode) and negative electrode (cathode). Include state symbols
for all species. Describe what is observed at each electrode and comment on any
change in the colour and the acidity of the solution.
[7]
Half-equation at positive electrode (anode):
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Half-equation at negative electrode (cathode):
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Observation at positive electrode (anode):
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Observation at negative electrode (cathode):
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Change in colour (if any) of the solution:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Change in acidity (if any) of the solution:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
1532
– 16 –
5.
N12/4/CHEMI/HP2/ENG/TZ0/XX
The strength of a covalent bond is measured in terms of its bond enthalpy.
(a)
Define the term average bond enthalpy.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
1,3,5,7-tetranitro-1,3,5,7-tetrazocane, shown below, can be used as an explosive.
A
O
N
H
H
O
N
C
H
H
C
N
N
N
O
O
H
C
H
N
C
B
N
H
O
H
N
O
O
O
The following equation represents the thermal decomposition of the compound.
C4 H8 N8O8 (s) → 4N 2 (g) + 4CO (g) + 4H 2 O (g)
(This question continues on the following page)
1632
– 17 –
N12/4/CHEMI/HP2/ENG/TZ0/XX
(Question 5 continued)
(i)
Calculate the enthalpy change when 10.0 g of the compound decomposes, using
average bond enthalpy data from Table 10 of the Data Booklet and the following
additional average bond enthalpy data at 298 K.
Bond
∆H / kJ mol–1
C≡O
1072
N–O
201
N=O
607
[4]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
The CO molecule has dative covalent bonding. Identify a nitrogen-containing
positive ion which also has this type of bonding.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
1732
– 18 –
N12/4/CHEMI/HP2/ENG/TZ0/XX
(Question 5 continued)
(iii) Describe in words and with the aid of a suitable diagram the difference between
sigma (σ) and pi (π) bonds.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv) Determine the number of σ and π bonds in 1,3,5,7-tetranitro-1,3,5,7-tetrazocane,
using the Lewis structure shown on page 16.
σ bonds:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . π bonds:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [2]
(This question continues on the following page)
1832
– 19 –
N12/4/CHEMI/HP2/ENG/TZ0/XX
(Question 5 continued)
(v)
Explain the term hybridization and deduce the hybridization (sp, sp2 or sp3) of the
atoms labelled A and B in the diagram on page 16.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (c)
Methanol reacts with carbon monoxide to form ethanoic acid, CH3COOH (l).
CH 3OH (l) + CO (g) → CH 3COOH (l)
(i)
Predict the sign of the entropy change, ∆S, of the system and explain your answer.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Define the term standard enthalpy change of formation, ëH f Ö.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
1932
– 20 –
N12/4/CHEMI/HP2/ENG/TZ0/XX
(Question 5 continued)
(iii) The standard enthalpy change of formation of CO (g) is –111 kJ mol–1. Using Table
11 of the Data Booklet, determine the enthalpy change of the reaction, in kJ mol–1.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv) The standard entropy of CO (g) is 198 J K–1 mol–1. Using Table 11 of the Data
Booklet, determine the standard entropy change of the reaction, in J K–1 mol–1.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (v)
Determine the standard free energy change for the reaction at 298 K, in kJ mol–1,
using your answers from (iii) and (iv) and state whether the reaction is spontaneous
or not.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (vi) In industry, this reaction is carried out at a temperature greater than 298 K. State and explain the effect of increasing the temperature on the value of the
equilibrium constant, Kc.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2032
– 21 –
6.
N12/4/CHEMI/HP2/ENG/TZ0/XX
Chemical kinetics involves an understanding of how the molecular world changes with time.
(a)
(i)
Define the term rate of reaction.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Temperature and the addition of a catalyst are two factors that can affect the rate of
a reaction. State two other factors.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) In the reaction represented below, state one method that can be used to measure
the rate of the reaction.
ClO3− (aq) + 5Cl− (aq) + 6H + (aq) → 3Cl2 (aq) + 3H 2 O (l)
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
2132
– 22 –
N12/4/CHEMI/HP2/ENG/TZ0/XX
(Question 6 continued)
(b)
A catalyst provides an alternative pathway for a reaction, lowering the activation energy, Ea.
(i)
Define the term activation energy, Ea.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Sketch the two Maxwell–Boltzmann energy distribution curves for a fixed amount
of gas at two different temperatures, T1 and T2 (T2 > T1). Label both axes.
[3]
(This question continues on the following page)
2232
– 23 –
N12/4/CHEMI/HP2/ENG/TZ0/XX
(Question 6 continued)
(c)
Sketch graphical representations of the following reactions, for X → products.
(i)
Concentration of reactant X against time for a zero-order reaction.
[1]
[X]
t
(ii)
Rate of reaction against concentration of reactant X for a zero-order reaction.
[1]
Rate
[X]
(iii) Rate of reaction against concentration of reactant X for a first-order reaction.
[1]
Rate
[X]
(This question continues on the following page)
Turn over
2332
– 24 –
N12/4/CHEMI/HP2/ENG/TZ0/XX
(Question 6 continued)
(d)
For the reaction below, consider the following experimental data.
2ClO 2 (aq) + 2OH − (aq) → ClO3− (aq) + ClO 2 − (aq) + H 2 O (l)
Experiment
(i)
Initial [ClO2 (aq)] / Initial [OH– (aq)] /
mol dm–3
mol dm–3
Initial rate /
mol dm–3 s–1
1
1.00 ×10−1
1.00 ×10−1
2.30 ×10−1
2
5.00 ×10−2
1.00 ×10−1
5.75 ×10−2
3
5.00 ×10−2
3.00 ×10−2
1.73 ×10−2
[2]
Deduce the rate expression.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
2432
– 25 –
N12/4/CHEMI/HP2/ENG/TZ0/XX
(Question 6 continued)
(ii)
Determine the rate constant, k, and state its units, using the data from Experiment 2.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) Calculate the rate, in mol dm–3 s–1, when [ClO 2 (aq)] = 1.50 ×10−2 mol dm −3 and
[OH − (aq)] = 2.35 ×10−2 mol dm −3 .
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (e)
Another reaction involving OH– (aq) is the base hydrolysis reaction of an ester.
CH 3COOCH 2 CH 3 (aq) + OH − (aq) → CH 3COO − (aq) + CH 3CH 2 OH (aq)
(i)
[1]
Apply IUPAC rules to name the ester, CH3COOCH2CH3 (aq).
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Describe qualitatively the relationship between the rate constant, k, and
temperature, T.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
2532
– 26 –
N12/4/CHEMI/HP2/ENG/TZ0/XX
(Question 6 continued)
(iii) The rate of this reaction was measured at different temperatures and the following
data were recorded.
–0.40
–0.60
–0.80
–1.00
ln k
–1.20
–1.40
–1.60
–1.80
–2.00
3.00
3.10
3.20
3.30
3.40
1
/ K −1 × 10−3
T
Using data from the graph, determine the activation energy, Ea , correct to three
significant figures and state its units.
[4]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
2632
– 27 –
N12/4/CHEMI/HP2/ENG/TZ0/XX
(Question 6 continued)
(f)
A two-step mechanism has been proposed for the following reaction.
(i)
Step 1:
ClO − (aq) + ClO − (aq) → ClO 2 − (aq) + Cl− (aq)
Step 2:
ClO 2 − (aq) + ClO − (aq) → ClO3− (aq) + Cl− (aq)
[1]
Deduce the overall equation for the reaction.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
[2]
Deduce the rate expression for each step.
Step 1:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Step 2:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
2732
– 28 –
7.
N12/4/CHEMI/HP2/ENG/TZ0/XX
Alkenes, alcohols and esters are three families of organic compounds with many commercial uses.
(a)
(i)
State what is meant by the term stereoisomers.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
X is an isomer of C4H8 and has the structural formula shown below.
H
H
H
H
C
C
C
H
H
C
H
H
Apply IUPAC rules to name this isomer. Deduce the structural formulas of two
other isomers of C4H8.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) State the balanced chemical equation for the reaction of X with HBr to form Y.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
2832
– 29 –
N12/4/CHEMI/HP2/ENG/TZ0/XX
(Question 7 continued)
(iv) Y reacts with aqueous sodium hydroxide, NaOH (aq), to form an alcohol, Z. Identify whether Z is a primary, secondary or tertiary alcohol.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Explain one suitable mechanism for the reaction in (iv) using curly arrows to
represent the movement of electron pairs.
[4]
(vi) Deduce the structural formula of the organic product formed when Z is oxidized
by heating under reflux with acidified potassium dichromate(VI).
[1]
(v)
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
2932
– 30 –
N12/4/CHEMI/HP2/ENG/TZ0/XX
(Question 7 continued)
(b)
An ester which gives apples their characteristic smell contains C, H and O. When
3.00 ×10−3 g of this ester were completely combusted, 6.93 ×10−3 g of CO2 and
2.83 ×10−3 g of H2O were produced.
(i)
Determine the empirical formula of the ester, showing your working.
[4]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
The molar mass of the ester is 116.18 g mol–1. Determine its molecular formula.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) Other than its use in food flavouring, state one use of esters.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
3032
– 31 –
N12/4/CHEMI/HP2/ENG/TZ0/XX
(Question 7 continued)
(c)
(i)
(ii)
When 2-bromobutane is refluxed with ethanolic potassium hydroxide (i.e. hydroxide
ions in ethanol), an elimination reaction occurs in which two different organic
products are formed. Explain the mechanism of this reaction, using curly arrows
to represent the movement of electron pairs, to show the formation of one of the
organic products.
[4]
Draw the structural formula of the other organic product and draw the structure of
an isomer of either product.
[2]
(This question continues on the following page)
Turn over
3132
– 32 –
N12/4/CHEMI/HP2/ENG/TZ0/XX
(Question 7 continued)
(iii) 2-bromobutane is optically active. Draw the two enantiomers of 2-bromobutane
and compare their physical and chemical properties.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3232
[2]
N12/4/CHEMI/HP2/ENG/TZ0/XX/M
MARKSCHEME
November 2012
CHEMISTRY
Higher Level
Paper 2
26 pages
–2–
N12/4/CHEMI/HP2/ENG/TZ0/XX/M
This markscheme is confidential and for the exclusive use of
examiners in this examination session.
It is the property of the International Baccalaureate and must not
be reproduced or distributed to any other person without the
authorization of the IB Assessment Centre.
–5–
N12/4/CHEMI/HP2/ENG/TZ0/XX/M
Subject Details: Chemistry HL Paper 2 Markscheme
Mark Allocation
Candidates are required to answer ALL questions in Section A [40 marks] and TWO questions in
Section B [2 x 25 marks]. Maximum total = [90 marks].
1.
A markscheme often has more marking points than the total allows. This is intentional.
2.
Each marking point has a separate line and the end is shown by means of a semicolon (;).
3.
An alternative answer or wording is indicated in the markscheme by a slash (/). Either wording can
be accepted.
4.
Words in brackets ( ) in the markscheme are not necessary to gain the mark.
5.
Words that are underlined are essential for the mark.
6.
The order of marking points does not have to be as in the markscheme, unless stated otherwise.
7.
If the candidate’s answer has the same “meaning” or can be clearly interpreted as being of
equivalent significance, detail and validity as that in the markscheme then award the mark.
Where this point is considered to be particularly relevant in a question it is emphasized by
OWTTE (or words to that effect).
8.
Remember that many candidates are writing in a second language. Effective communication is more
important than grammatical accuracy.
9.
Occasionally, a part of a question may require an answer that is required for subsequent
marking points. If an error is made in the first marking point then it should be penalized. However,
if the incorrect answer is used correctly in subsequent marking points then follow through marks
should be awarded. When marking, indicate this by adding ECF (error carried forward) on the
script.
10.
Do not penalize candidates for errors in units or significant figures, unless it is specifically referred
to in the markscheme.
11.
If a question specifically asks for the name of a substance, do not award a mark for a correct
formula unless directed otherwise in the markscheme, similarly, if the formula is specifically asked
for, unless directed otherwise in the markscheme do not award a mark for a correct name.
12.
If a question asks for an equation for a reaction, a balanced symbol equation is usually expected, do
not award a mark for a word equation or an unbalanced equation unless directed otherwise in the
markscheme.
13.
Ignore missing or incorrect state symbols in an equation unless directed otherwise in the
markscheme.
–6–
N12/4/CHEMI/HP2/ENG/TZ0/XX/M
SECTION A
1.
(a)
(i)
(ii)
I2(s): four/4 and ICl(l): three/3;
[1]
⎛ 2.24
⎞
–2
n (Cl2 ) = ⎜
= ⎟ 0.0316 /3.16 × 10 (mol);
⎝ 2 × 35.45 ⎠
Allow answers such as 3.2 × 10–2/0.032/3.15 × 10–2/0.0315 (mol).
n(ICl) = 2 × 0.0316 / 0.0632/6.32 × 10–2 (mol);
Allow answers such as 6.4 × 10–2/0.064/6.3 × 10–2/0.063 (mol).
m (ICl) = (0.0632 ×162.35 =) 10.3 (g) ;
Allow answers in range 10.2 to 10.4 (g).
Award [3] for correct final answer.
⎛ 8.60
⎞
(iii) ⎜
×100 = ⎟ 83.5% ;
⎝ 10.3
⎠
Allow answers in the range of 82.5 to 84.5%.
(iv) negative/–/minus/ < 0 ;
(b)
(c)
Br2 has London/dispersion/van der Waals’ forces/vdW and ICl has (London/
dispersion/van der Waals’ forces/vdW and) dipole–dipole forces;
dipole–dipole forces are stronger than London/dispersion/van der Waals’/vdW
forces ;
Allow induced dipole-induced dipole forces for London forces.
Allow interactions instead of forces.
Do not allow ICl polar and Br2 non-polar for M1.
Name of IMF in both molecules is required for M1 and idea of dipole-dipole
stronger than vdW is required for M2.
(i)
(ii)
⎛ 126.90
⎞
×100 ⎟ = 38.4 % ;
⎜
⎝ 330.71
⎠
(25.25 − 1.05) = 24.20 (cm3 ) ;
Accept 24.2 (cm3) but not 24 (cm3).
⎛ 24.20 × 5.00 ×10−2 ⎞
−3
(iii) ⎜
⎟ = 1.21×10 /0.00121(mol) ;
1000
⎝
⎠
(iv)
(0.5 ×1.21×10−3 ) = 6.05 ×10−4 /0.000605(mol) ;
Accept alternate method e.g. (0.384/126.9 × 0.2015) = 6.10 × 10–4/0.000610 (mol).
[3]
[1]
[1]
[2]
[1]
[1]
[1]
[1]
–7–
(v)
(vi)
(d)
N12/4/CHEMI/HP2/ENG/TZ0/XX/M
(126.90 × 6.05 ×10−4 ) = 7.68 ×10−2 /0.0768(g) ;
Accept alternate method e.g. (6.10 × 10–4 × 126.9) or (0.2015 × 0.384) = 7.74 ×
10–2/0.00774 (g).
⎛ 7.68 ×10−2
⎞
×100 ⎟ = 38.1 % ;
⎜
⎝ 0.2015
⎠
Answer must be given to three significant figures.
[1]
ICl / iodine monochloride;
Do not accept iodine or bromine.
(e)
[1]
[1]
ICl3
ICl2–
Lewis (electron
dot) structure
Do not penalize for an incorrect shape for Lewis structures.
Accept lines, dots or crosses for electron pairs for both Lewis
structures.
Penalize missing lone pairs on Cl once only.
Square brackets and negative charge must be shown for
Lewis structure of [ICl2]–.
Name of shape
T-shaped;
linear;
[4]
No ECF for shape if Lewis structure is incorrect.
(f)
(i)
1s2 2s2 2p6 3s 2 3p6 4s 2 3d10 4p6 5s 2 4d10 5p5 /1s 2 2s 2 2p 6 3s 2 3p 6 3d10 4s 2 4p 6 4d10 5s2 5p5 ;
No mark for 2,8,18,18,7 or [Kr] 5s24d105p5.
Allow electron configurations with order of sublevels interchanged.
Electrons must be represented as superscript to award mark.
[1]
–8–
(ii)
N12/4/CHEMI/HP2/ENG/TZ0/XX/M
Cl2(aq) H2O(l) HCl(aq) HOCl(aq);
Accept .
Accept HClO(aq).
Allow H+(aq) Cl–(aq) for HCl(aq) and H+(aq) –OCl(aq)/OCl–(aq)/ClO–(aq)
for HOCl(aq).
Allow 2Cl2 (g) 2H 2O(l) 4HCl(aq) O2 (g) .
Ignore state symbols.
[1]
(iii) Monomer:
/ chloroethene /CH2CHCl;
Accept vinyl chloride or chloroethylene.
Allow C2H3Cl.
Use:
raincoats / packaging / window frames / pipes / carpets / gutters / electrical cable
sheathing / covers for electrical wires / rope / bottles;
Accept suitable alternatives.
Do not allow glue.
Do not allow just plastic(s) or just windows.
Allow plastic bag.
[2]
–9–
2.
(a)
(i)
(ii)
N12/4/CHEMI/HP2/ENG/TZ0/XX/M
Group: (elements in vertical) columns in periodic table and Period: (elements
in horizontal) rows in periodic table;
Allow elements in same group have similar chemical properties and within a
period, atoms have same number of shells/energy levels (but number of
electrons in valence/outer shell increases).
Allow groups distributed vertically and periods distributed horizontally /
OWTTE.
Allow group number gives number of valence/outer shell electrons (for maingroup elements) and period gives same number of shells/energy levels.
Mass number
(A)
Number of
protons
Number of
electrons
Number of
neutrons
6
3
3
3
;
7
3
3
4
;
[1]
[2]
Award [1 max] for correct number of neutrons for both isotopes if numbers of
protons or electrons is not given.
Award [1 max] for correct number of protons and electrons for both isotopes if
number of neutrons is not given or if numbers of neutrons are incorrect.
(iii) symmetrical shape of s orbital and dumbbell-shaped p orbital with electron
density along x-axis;
y
y
x
x
z
z
(b)
(i)
(ii)
[1]
metals have delocalized electrons / sea of electrons which are mobile/can
move / OWTTE;
layers/positive ions/cations/atoms slide past/over each other / OWTTE;
Do not accept nuclei for M2.
↿⇂
1s
↿ ⇂ 2s
↿ ⇂ ↿ ⇂ ↿ ⇂ 2p
↿⇂
3s
↿⇂ ↿⇂ ↿⇂
3p
↿⇂ ↿
4s
↿ ↿
3d
[2]
↿
[1]
Allow full arrows instead of half-arrows for example ↑↓.
Do not allow arrows with the same spin for example ↑↑ or ↓↓ in the same
orbital.
Do not allow an orbital diagram with a 4s13d5configuration.
– 10 –
(iii)
Co 2 ;
Accept +2, 2+, cobalt(II), II.
N12/4/CHEMI/HP2/ENG/TZ0/XX/M
[1]
(iv) partially filled/incomplete d subshell/sub-level/orbitals;
d orbitals split (into two sets of different energies);
(colour due to) electron transition between (split) d orbitals / d to d transitions /
frequencies of visible light absorbed by electrons moving from lower to higher
d levels ;
colour due to remaining frequencies / complementary colour seen;
[3 max]
Allow wavelength as well as frequency.
– 11 –
3.
(a)
(b)
N12/4/CHEMI/HP2/ENG/TZ0/XX/M
(solution containing significant/equal amounts of a) weak acid and its salt / (solution
containing) strong base to which excess of weak acid has been added / OWTTE;
Accept (solution containing) weak acid and conjugate base.
Do not accept descriptions with specific compounds alone (e.g. CH3COOH and
CH3COONa) unless compounds are stated as weak acid and its salt.
Accept answer such as (solution containing) x mol of weak acid and 21 x mol of
strong base.
[1]
M r (CH3COOH) = 60.06 and M r CH3COONa = 82.04 ;
[CH3COOH] = 6.66 ×10−1 /0.666 mol dm −3 ;
[CH3COO − ] = 4.88 ×10−1 / 0.488 mol dm −3 ;
[H3O+ ] / [H + ] = (1.8 ×10−5 × 6.66 ×10−1 )/4.88 ×10−1 = 2.46 ×10−5 / 0.0000246 mol dm −3 ;
pH = ( − log[H3O+ ] = − log (2.46 ×10−5 ) = ) 4.61(2dp) ;
Award [5] for correct final answer of pH = 4.61 with some working shown.
Award [2 max] for pH = 4.61 without any working at all shown.
Two decimal places are required for M5.
OR
M r (CH3COOH) = 60.06 and M r CH3COONa = 82.04 ;
[CH3COOH] = 6.66 ×10−1 /0.666 mol dm −3 ;
[CH 3COO − ] = 4.88 ×10−1 /0.488 mol dm −3 ;
pH = −log (1.8 ×10−5 ) + log
[salt]
;
[acid]
0.488
⎛
⎞
= ⎜ 4.74 + log
= 4.74 − 0.135 = ⎟ 4.61 (2dp) ;
0.666
⎝
⎠
M4 can be scored even if not explicitly stated if M5 is correct based on previous
values.
Award [5] for correct final answer of pH = 4.61 with some working shown.
Award [2 max] for pH = 4.61 without any working at all shown.
Two decimal places are required for M5.
[5]
– 12 –
N12/4/CHEMI/HP2/ENG/TZ0/XX/M
SECTION B
4.
(a)
(i)
Oxidation: loss of electrons and Reduction: gain of electrons;
(ii)
As2O3: 3 ;
NO3–: 5 ;
H3AsO3: 3 ;
N2O3: 3 ;
Penalize incorrect notation e.g. III, V, 3+, 5+, 3, 5 once only.
(iii) Oxidizing agent: substance reduced / removes electrons from another
substance / causes some other substance to be oxidized / OWTTE and
Reducing agent: substance oxidized / gives electrons to another substance /
causes some other substance to be reduced / OWTTE;
Accept Oxidizing agent: electron/e/e– acceptor / causes oxidation /
oxidation number/state decreases and Reducing agent: electron/e/e– donor /
causes reduction / oxidation number/state increases.
(iv)
[1]
[4]
[1]
As 2 O3 (s) 2NO3 (aq) 2H (aq) 2H 2 O (l) 2H3 AsO 4 (aq) N 2 O3 (aq)
correct coefficients for As 2 O3 , H 3 AsO 4 and NO3 , N 2 O3 ;
correct balanced equation;
Ignore state symbols.
M1 must be correct to award M2.
Oxidizing agent: NO3 (aq) /nitrate and Reducing agent: As 2 O3 (s) /
arsenic(III) oxide;
Accept HNO3(aq)/nitric acid.
Accept arsenic oxide.
Species must be fully correct to score M3.
Ignore state symbols.
[3]
– 13 –
(b)
(i)
N12/4/CHEMI/HP2/ENG/TZ0/XX/M
Diagram to show:
electron
flow
+
–
Labels are not required.
one container, two electrodes, battery (and electrolyte);
Allow + and – for representation of battery (could be long and short lines for
example) but M1 is not scored if a voltmeter/V if shown or labelled.
Ignore designation of electrodes (e.g. do not penalize Cu electrodes).
correct direction of electron flow (from negative pole to positive pole);
Allow arrow without stating e– explicitly.
To score M2, the polarity of the battery or the cathode and anode must be
shown.
If a voltmeter/V is shown, M1 is not awarded but M2 may be scored if the
cathode and anode are identified with the correct direction of electron flow.
[2]
– 14 –
(ii)
N12/4/CHEMI/HP2/ENG/TZ0/XX/M
Half-equation at positive electrode (anode):
4OH (aq) 2H 2 O (l) O 2 (g) 4e / 2H 2 O (l) O 2 (g) 4H (aq) 4e /
1
2OH (aq) O 2 (g) H 2 O(l) 2e ;
2
Allow e instead of e–.
Half-equation at negative electrode (cathode):
Cu 2 (aq) 2e Cu (s) ;
Allow e instead of e–.
Award [1 max] for M1 and M2 if correct equations are given but at wrong
electrodes.
Penalize once only in (b)(ii) and (b)(iii).
correct state symbols in all equations;
M3 can only be scored if the correct species are given in M1 and M2 (i.e. do
not award ECF from M1 and M2 for incorrect species).
Observation at positive electrode (anode):
bubbles / gas;
Award mark for observation even if type of gas is incorrect (e.g. hydrogen).
Observation at negative electrode (cathode):
red/brown/copper/metal (deposit);
Allow mass increases / gets thicker/larger / OWTTE.
Change in colour (in any) of the solution:
solution loses blue colour/becomes paler;
Change in acidity (if any) of the solution:
becomes (more) acidic / pH decreases;
(iii) Half-equation at positive electrode (anode):
Cu (s) Cu 2 (aq) 2e – ;
Allow e instead of e–.
Half-equation at negative electrode (cathode):
Cu 2 (aq) 2e – Cu (s) ;
Allow e instead of e–.
Award [1 max] for M1 and M2 if correct equations are given but at wrong
electrodes.
Penalize once only in (b)(ii) and (b)(iii).
correct state symbols in all equations;
M3 can only be scored if the correct species are given in M1 and M2 (i.e. do
not award ECF from M1 and M2 for incorrect species).
Observation at positive electrode (anode):
(slowly) dissolves / OWTTE;
Allow mass decreases / gets smaller/thinner / OWTTE;
Accept impurities deposited under positive electrode/anode.
[7]
– 15 –
N12/4/CHEMI/HP2/ENG/TZ0/XX/M
Observation at negative electrode (cathode):
red/brown/copper/metal deposit;
Allow mass increases / gets thicker/larger / OWTTE.
Change in colour (if any) of the solution:
blue colour remains;
Allow no change or solution remains same colour.
Change in acidity (if any) of the solution:
solution does not become (more) acidic / no change / OWTTE;
[7]
– 16 –
5.
(a)
(b)
N12/4/CHEMI/HP2/ENG/TZ0/XX/M
energy needed to break (1 mol of) a bond in a gaseous molecule/state/phase;
average calculated from a range of similar compounds / OWTTE;
Do not accept similar bonds instead of similar compounds.
M2 can be scored independently.
(i)
[2]
Bonds breaking:
4 (NO) 4 (NN) 8 (CH) 4 (N O) 8 (CN) /
(4)(607) (4)(158) (8)(413) (4)(201) (8)(286) /
9456 (kJ mol1 ) ;
Bonds forming:
4 (NN) 4 (CO) 8 (O H) /
(4)(945) (4)(1072) (8)(464)/ 11780 (kJ mol1 ) ;
Enthalpy change:
(9456 11780 ) 2324 (kJ mol 1 ) ;
M3 is scored from M1-M2.
Award [2 max] for (+)2324 (kJ mol–1).
Award [3] for –2324 (kJ mol–1) without working.
2324 78.5 (kJ) ;
10.0 296.2
M4 is scored from 10.0/296.2 M3.
Allow answers of –78.2, –78 and –79 (kJ), but negative sign must be included.
Award [4] for correct final answer.
(ii)
NH4+/ammonium / N2H5+/hydrazinium
methanaminium / H2NO3+ /nitrooxonium;
/
[4]
CH3NH3+/methylammonium/
[1]
(iii) Sigma bonds:
result from head-on/end-on overlap of orbitals / OWTTE;
Allow symmetric (orbital) with respect to same plane / OWTTE.
Pi bonds:
result from sideways overlap of orbitals / OWTTE;
Allow antisymmetric (orbitals) with respect to (defining) plane (containing at
least one atom) / OWTTE.
suitable diagrams showing and after formation;
Award [1 max] for correct diagram without description given or [2 max] for
description given without diagram.
[3]
– 17 –
(iv)
(v)
(c)
(i)
(ii)
N12/4/CHEMI/HP2/ENG/TZ0/XX/M
bonds: 28;
bonds: 4;
mixing/combining/merging of atomic orbitals to form new/molecular orbitals
(for bonding);
A: sp 2 ;
B: sp3 ;
Award [1 max] for M2 and M3 for sp2 and sp3 if A and B are not identified
explicitly but do not award M2 and M3 if sp3 is given for A and sp2 for B.
(entropy decreases) negative/-/minus;
gaseous reactant more disordered / product more ordered than reactants /
amount of gas decreases / OWTTE;
Allow number of moles of gas decreases.
M2 can only be scored if M1 is correct.
heat/enthalpy change when 1 mol of a compound is formed from its elements;
in their standard states / at 100 kPa/105 Pa/1bar (pressure);
Allow 1.01 10 5 Pa / 101kPa / 1 atm .
Allow under standard conditions or standard ambient temperature and
pressure.
Temperatures not required in definition, allow if quoted (e.g. 298 K/ 25 C –
most common) but correct pressure value must be stated if given.
Only award M2 for a correct M1 or a near miss at M1.
[2]
[3]
[2]
[2]
(iii)
H (485 111 239 ) 135 (kJ mol1 ) ;
[1]
(iv)
S (160 198 240) 278 (J K 1 mol 1 ) ;
[1]
(v)
278 G H T S 135 298 52.2 (kJ mol1 ) ;
1000
spontaneous (since negative G ) ;
Answer to M2 depends on sign given in M1.
(vi) (Kc) decreases;
exothermic / H 0;
M1 and M2 depend on sign of H in (iii).
[2]
[2]
– 18 –
6.
(a)
(i)
(ii)
N12/4/CHEMI/HP2/ENG/TZ0/XX/M
change in concentration of reactant/product with time / rate of change of
concentration;
Increase can be used instead of change for product or decrease can be used
instead of change for reactant.
Allow mass/amount/volume instead of concentration.
Do not accept substance.
concentration;
particle size / surface area;
light;
pressure;
Allow pH.
(iii) (measuring electrical) conductivity / (measuring) pH;
Accept other suitable method.
(b)
(i)
(ii)
minimum/least/smallest energy needed (by reactants/colliding particles) to
react/start/initiate a reaction;
Allow energy difference between reactants and transition state.
Minimum/least/smallest required for the mark.
[1]
[2 max]
[1]
[1]
x-axis label: (kinetic) energy/(K)E and y-axis label: probability/fraction of
molecules/particles / probability density;
Allow number of molecules/particles for y-axis.
correct shape of a typical Maxwell–Boltzmann energy distribution curve;
Do not award mark if curve is symmetric, does not start at zero or if it crosses
x-axis.
two curves represented with second curve for T2 T1 to right of first curve,
peak maximum lower than first curve and after the curves cross going to the
right, T2 curve needs to be above T1 curve as illustrated;
M2 and M3 can be scored independently.
[3]
– 19 –
(c)
(i)
N12/4/CHEMI/HP2/ENG/TZ0/XX/M
[X]
;
t
(ii)
[1]
Rate
;
[X]
[1]
(iii) Rate
;
[X]
(d)
(i)
second order in ClO 2 and first order in OH ;
rate k [ClO 2 ]2 [OH ] ;
Award [2] for correct final answer.
(ii)
(e)
[1]
k 2.30 102 /230;
mol2 dm 6 s 1 ;
[2]
[2]
(iii) 1.22 10 3 /0.00122 (mol dm–3 s–1);
[1]
(i)
ethyl ethanoate;
Do not allow ethyl acetate.
[1]
(ii)
as temperature/T increases, (value of) rate constant/k increases (exponentially);
Do not allow answers involving ln k from the Arrhenius equation.
Do not allow T directly proportional to k.
[1]
– 20 –
N12/4/CHEMI/HP2/ENG/TZ0/XX/M
(iii) slope = −5.6 ×103 / −5600 (K);
Ea = − slope × R / slope = − Ea / R ;
Ea (= 5.60 ×103 K × 8.31J K −1 mol −1 ) = 4.65 ×10 4 (J mol–1) / 46.5 (kJ mol–1);
Accept answers in range 4.60 × 10 4 J mol −1 to 4.67 × 10 4 J mol −1 .
J mol−1 / kJ mol–1;
Accept J or kJ.
Unit mark can be scored independently but correct Ea values with incorrect
units scores only [3 max] (for example 46.5 J mol–1).
[4]
Award [4] for correct final answer.
(f)
(i)
3ClO − (aq) → ClO3− (aq) + 2Cl− (aq) ;
Ignore state symbols.
(ii)
Step 1: rate = k[ClO− ]2 ;
Step 2: rate = k[ClO 2 − ][ClO − ] ;
Penalize missing k once only.
[1]
[2]
– 21 –
N12/4/CHEMI/HP2/ENG/TZ0/XX/M
Penalize missing hydrogens or incorrect bonding (e.g. C–H3C) once only in 7.
7.
(a)
(i)
(ii)
compounds with same structural/displayed formula but different arrangements
of atoms (in space);
Do not accept different 3D structures.
Do not allow similar instead of same.
[1]
(cis-)but-2-ene / (Z)but-2-ene / but-2-ene;
Accept (cis-)2-butene / Z-2-butene.
Ignore missing hyphens.
CH3CH2CH=CH2 ;
H 2C=C(CH3 )2 ;
Accept either full or condensed structural formulas.
Allow structural formula of trans-but-2-ene. Accept other alternative suitable
isomers.
[3]
(iii) (CH3 )CH=CH(CH3 ) + HBr → CH3CHBrCH2CH3 ;
Allow C4 H 8 + HBr → C4 H 9 Br .
[1]
(iv) secondary/ 2o ;
[1]
(v)
Since secondary could be either SN1 or SN2 so allow SN1 or SN2 for M1–M4.
SN1:
curly arrow showing Br leaving;
Do not allow arrow originating from C to C–Br bond.
representation of secondary carbocation;
curly arrow going from lone pair/negative charge on O in HO– to C+;
Do not allow arrow originating on H in HO–.
formation of organic product CH3CH(OH)C2H5/C4H9OH and Br–;
Allow formation of NaBr instead of Br–.
– 22 –
N12/4/CHEMI/HP2/ENG/TZ0/XX/M
OR
SN2:
curly arrow going from lone pair/negative charge on O in HO– to C;
Do not allow curly arrow originating on H in HO–.
curly arrow showing Br leaving;
Accept curly arrow either going from bond between C and Br to Br in
2-bromobutane or in the transition state.
Do not allow arrow originating from C to C–Br bond.
representation of transition state showing negative charge, square brackets
and partial bonds;
Do not penalize if HO and Br are not at 180 to each other.
Do not award M3 if OH ---- C bond is represented.
formation of organic product CH3CH(OH)C2H5/C4H9OH and Br–;
Allow formation of NaBr instead of Br–.
[4]
For primary Z from (iv), for ECF SN2 required.
For tertiary Z from (iv), for ECF SN1 required.
But curly arrow showing Br leaving and formation of C4H9OH and Br– can
be scored for either mechanism (even if incorrect type).
For primary Z from (iv) with 1-bromobutane stated in (v), correct SN2 can
score full marks.
If (iv) is not answered and incorrect starting reagent is given in (v), M1, M2
and M3 may be scored but not M4 for either correct SN1 or SN2.
(vi) CH3COCH2CH3;
Full or condensed structural formula may be given.
For primary Z from (iv), accept CH3CH2CH2COOH/C3H7COOH but not
CH3CH2CH2CHO.
[1]
– 23 –
(b)
(i)
N12/4/CHEMI/HP2/ENG/TZ0/XX/M
6.93 103 12.01
Mass of C:
1.89 103 /0.00189 (g) and
44.01
2 1.01 2.83 103
3.17 104 /0.000317 (g);
Mass of H:
18.02
Mass of O: 3.00 103 1.89 103 3.17 104 7.93 104 /0.000793 (g);
1.89 103
nC :
1.57 104 /0.000157 (mol) and
12.01
3.17 104
3.14 104 /0.000314 (mol) and
nH:
1.01
7.93 104
4.96 105 /0.0000496 (mol) ;
nO:
16.00
Empirical formula C3 H 6 O ;
Allow C19H38O6.
Award [4] for correct final answer if alternative working is used.
Award [1 max] for C3H6O/C19H38O6 without working.
(ii)
C6 H12 O 2 ;
(iii) fragrances/perfumes / solvents / plasticizers / adhesives/glue / biodiesel;
Accept a named painkiller (e.g. aspirin) or anaesthetic (e.g. procaine,
benzocaine) containing the ester functional group.
Accept “some painkillers”.
Allow a specific named polyester (e.g. polyethylene terephthalate/PET), but
polyester alone is not sufficient to score the mark.
[4]
[1]
[1]
– 24 –
(c)
(i)
N12/4/CHEMI/HP2/ENG/TZ0/XX/M
Accept either one of the following two E2 mechanisms:
OR
curly arrow going from lone pair/negative charge on O in HO to H on –C;
Do not allow curly arrow originating on H in HO–.
curly arrow going from CH bond to form C=C bond;
curly arrow showing Br leaving;
formation of organic product H 2 C=CH(CH 2 CH 3 ) / H(CH3 )C=CH(CH3 ) and
Br– and H 2 O ;
For this reaction since a strong negatively charged base, HO– is used,
resultant mechanism will be E2. However, accept the corresponding E1
mechanism.
– 25 –
N12/4/CHEMI/HP2/ENG/TZ0/XX/M
If E1, allow the following mechanism:
OR
curly arrow showing Br leaving;
representation of secondary carbocation;
curly arrow going from lone pair on O in H 2 O to H on C adjacent to C and curly
arrow going from CH bond to form C=C bond;
formation of organic product (H 3C)CH=CH(CH3 ) / H 2 C=CH(CH 2 CH 3 ) and Br and H 3O ;
For E1 HO- is an alternative to H2O, but if used, H2O forms instead of H3O+.
[4]
– 26 –
(ii)
N12/4/CHEMI/HP2/ENG/TZ0/XX/M
Depending on product in (i):
[2]
(iii) 3D representation of two enantiomers of 2-bromobutane;
Tapered (wedge/dash) notation not necessary but non-superimposeable mirror
images must be shown clearly.
two optical isomers rotate plane of plane-polarized light in (equal and) opposite
directions (all other physical properties identical) and identical chemical
properties (in reactions with non-chiral compounds) / OWTTE;
Allow different chemical properties only if reference is made to their reaction
with other optically active compounds/chiral reagents / biological sensors /
OWTTE.
[2]
M13/4/CHEMI/HPM/ENG/TZ1/XX
22136107
CHEMISTRY
HIGHER LEVEL
PAPER 1
Thursday 16 May 2013 (afternoon)
1 hour
INSTRUCTIONS TO CANDIDATES
• Do not open this examination paper until instructed to do so.
• Answer all the questions.
• For each question, choose the answer you consider to be the best and indicate your choice on
the answer sheet provided.
• The periodic table is provided for reference on page 2 of this examination paper.
• The maximum mark for this examination paper is [40 marks].
2213-6107
19 pages
© International Baccalaureate Organization 2013
2213-6107
23
V
50.94
87
Fr
(223)
88
Ra
(226)
‡
†
89 ‡
Ac
(227)
90
Th
232.04
58
Ce
140.12
91
Pa
231.04
59
Pr
140.91
73
Ta
180.95
38
Sr
87.62
37
Rb
85.47
22
Ti
47.90
56
57 †
72
55
Ba
La
Cs
Hf
132.91 137.34 138.91 178.49
20
Ca
40.08
19
K
39.10
41
Nb
92.91
39
Y
88.91
12
Mg
24.31
11
Na
22.99
92
U
238.03
60
Nd
144.24
74
W
183.85
42
Mo
95.94
24
Cr
52.00
Relative atomic mass
Element
Atomic number
40
Zr
91.22
21
Sc
44.96
4
Be
9.01
2
3
Li
6.94
1
H
1.01
1
30
Zn
65.37
93
Np
(237)
94
Pu
(242)
95
Am
(243)
96
Cm
(247)
97
Bk
(247)
98
Cf
(251)
61
66
62
63
64
65
Pm
Dy
Sm
Tb
Eu
Gd
146.92 150.35 151.96 157.25 158.92 162.50
75
80
76
77
78
79
Re
Os
Pt
Au
Hg
Ir
186.21 190.21 192.22 195.09 196.97 200.59
48
44
45
46
47
Cd
Ru
Rh
Pd
Ag
101.07 102.91 106.42 107.87 112.40
29
Cu
63.55
43
Tc
98.91
28
Ni
58.71
26
Fe
55.85
25
Mn
54.94
27
Co
58.93
The Periodic Table
50
Sn
118.69
32
Ge
72.59
14
Si
28.09
6
C
12.01
4
99
Es
(254)
100
Fm
(257)
67
68
Ho
Er
164.93 167.26
81
82
Tl
Pb
204.37 207.19
49
In
114.82
31
Ga
69.72
13
Al
26.98
5
B
10.81
3
101
Md
(258)
69
Tm
168.93
83
Bi
208.98
51
Sb
121.75
33
As
74.92
15
P
30.97
7
N
14.01
5
35
Br
79.90
17
Cl
35.45
9
F
19.00
7
85
At
(210)
102
No
(259)
103
Lr
(260)
70
71
Lu
Yb
173.04 174.97
84
Po
(210)
52
53
Te
I
127.60 126.90
34
Se
78.96
16
S
32.06
8
O
16.00
6
86
Rn
(222)
54
Xe
131.30
36
Kr
83.80
18
Ar
39.95
10
Ne
20.18
2
He
4.00
0
–2–
M13/4/CHEMI/HPM/ENG/TZ1/XX
–3–
1.
M13/4/CHEMI/HPM/ENG/TZ1/XX
What is the whole number ratio of the coefficients of ammonia to oxygen when the following equation
is balanced correctly?
___ NH 3 (g) + ___ O 2 (g) → ___ NO (g) + ___ H 2O (l)
2.
A.
1:2
B.
2:1
C.
4:5
D.
5:4
When 50 cm3 of a hydrocarbon, CxHy , was burned in excess oxygen, 200 cm3 of carbon dioxide and
250 cm3 of steam were produced (all volumes were measured under the same conditions). What is the
molecular formula of the hydrocarbon?
A.
C2H4
B.
C3H8
C.
C4H8
D.
C4H10
2213-6107
Turn over
–4–
3.
M13/4/CHEMI/HPM/ENG/TZ1/XX
Which graph represents the relationship between volume and pressure for a fixed mass of gas at
constant temperature?
A.
B.
V
V
P
C.
P
D.
V
V
P
4.
Which diagram shows a pattern similar to the emission spectrum of hydrogen?
Increasing wavelength
A.
B.
C.
D.
2213-6107
1
P
–5–
5.
6.
7.
M13/4/CHEMI/HPM/ENG/TZ1/XX
What is the correct electron configuration of the Cu+ ion?
A.
[Ar] 3d9 4s1
B.
[Ar] 3d7 4s2
C.
[Ar] 3d10
D.
[Ar] 3d8 4s1
Which statement concerning electronegativity is correct?
A.
Electronegativity increases from left to right across a period.
B.
Metals generally have higher electronegativity values than non-metals.
C.
Electronegativity increases on descending a group.
D.
Noble gases have the highest electronegativity values.
Which statements are correct?
I.
Fluorine will react with potassium chloride solution to produce chlorine.
II.
Iodine will react with sodium chloride solution to produce chlorine.
III.
Bromine will react with lithium iodide solution to produce iodine.
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
2213-6107
Turn over
–6–
8.
9.
10.
M13/4/CHEMI/HPM/ENG/TZ1/XX
Each of the following oxides is added to separate equal volumes of distilled water. Which of the
following is the most acidic oxide?
A.
P4O10
B.
SO3
C.
Cl2O7
D.
SiO2
What are the correct formulas of the following ions?
Nitrate
Sulfate
Phosphate
Hydrogencarbonate
A.
NO3–
SO42–
PO43–
HCO3–
B.
NO3–
SO42–
PO33–
HCO32–
C.
NO2–
SO4–
PO43–
HCO3–
D.
NO2–
SO32–
PO33–
HCO32–
Which compound is predominantly covalent?
A.
LiCl
B.
Al2O3
C.
ClF
D.
ZnCl2
2213-6107
–7–
11.
M13/4/CHEMI/HPM/ENG/TZ1/XX
Which combination best describes the type of bonding present and the melting point of silicon and
silicon dioxide?
Silicon
12.
Silicon dioxide
A.
covalent bonding
high melting point
covalent bonding
high melting point
B.
metallic bonding
high melting point
covalent bonding
low melting point
C.
ionic bonding
high melting point
ionic bonding
low melting point
D.
covalent bonding
low melting point
ionic bonding
high melting point
Which species has a square planar shape?
A.
B.
F
F
C
F
S
F
F
F
F
F
C.
D.
–
–
F
F
B
F
2213-6107
F
F
F
Cl
F
F
Turn over
–8–
13.
M13/4/CHEMI/HPM/ENG/TZ1/XX
What are the hybridizations of the atoms labelled 1, 2 and 3 in the molecule below?
O
H3C
1
14.
1
2
3
A.
sp2
sp2
sp
B.
sp3
sp2
sp3
C.
sp2
sp
sp3
D.
sp3
sp2
sp
C
2
O
3
H
Which statement is correct for the enthalpy level diagram shown?
Enthalpy
Enthalpy of
reactants
Enthalpy of
products
Time
A.
The reaction is exothermic and the products are more stable than the reactants.
B.
The reaction is exothermic and the sign of the enthalpy change is positive.
C.
The reaction is endothermic and the sign of the enthalpy change is negative.
D.
The reaction is endothermic and the products are more stable than the reactants.
2213-6107
–9–
15.
16.
17.
18.
M13/4/CHEMI/HPM/ENG/TZ1/XX
Which process is endothermic?
A.
2C4 H10 (g) + 13O 2 (g) → 8CO 2 (g) + 10H 2O (g)
B.
Na (g) → Na + (g) + e –
C.
H 2SO 4 (aq) + 2KOH (aq) → K 2SO 4 (aq) + 2H 2O (l)
D.
NH 3 (g) → NH 3 (l)
Which combination of ions will give the greatest absolute lattice enthalpy?
A.
A small positive ion with a high charge and a small negative ion with a high charge
B.
A small positive ion with a low charge and a small negative ion with a low charge
C.
A large positive ion with a high charge and a large negative ion with a high charge
D.
A large positive ion with a low charge and a small negative ion with a low charge
Which process would be expected to have a ëS Ö value which is negative?
A.
2H 2 (g) + O 2 (g) → 2H 2O (g)
B.
NaCl (s) → Na + (g) + Cl – (g)
C.
H 2 (g) + I 2 (g) → 2HI (g)
D.
OF2 (g) + H 2O (g) → O 2 (g) + 2HF (g)
When solid potassium chlorate, KClO3 , dissolves in distilled water the temperature of the solution
decreases. What are the signs of ëH Ö , ëS Ö and ëG Ö for this spontaneous process?
ëH Ö
ëS Ö
ëG Ö
A.
+
+
+
B.
+
+
–
C.
–
–
–
D.
+
–
+
2213-6107
Turn over
– 10 –
19.
M13/4/CHEMI/HPM/ENG/TZ1/XX
Which graph best represents the relationship between the average kinetic energy of molecules of a
gas and temperature in K?
Average kinetic energy
B.
Average kinetic energy
A.
Temperature / K
Average kinetic energy
D.
Average kinetic energy
C.
Temperature / K
Temperature / K
20.
Temperature / K
For the gas phase reaction:
A (g) + B(g) → C (g)
the experimentally determined rate expression is: rate = k [A] [B]2
By what factor will the rate change if the concentration of A is tripled and the concentration of B
is halved?
A.
0.75
B.
1.5
C.
6
D.
12
2213-6107
– 11 –
21.
M13/4/CHEMI/HPM/ENG/TZ1/XX
Which graph best represents a second-order reaction?
Concentration
of reactant
B.
Concentration
of reactant
A.
Time
Time
Concentration
of reactant
D.
Concentration
of reactant
C.
Time
22.
Time
Which changes occur when the temperature is decreased in the following equilibrium?
2BrCl (g) Br2 (g) + Cl 2 (g)
Position of equilibrium
Value of Kc
A.
shifts to the right
decreases
B.
shifts to the right
increases
C.
shifts to the left
decreases
D.
shifts to the left
increases
2213-6107
ëH Ö = –14 kJ
Turn over
– 12 –
23.
M13/4/CHEMI/HPM/ENG/TZ1/XX
When gaseous nitrosyl chloride, NOCl (g), decomposes, the following equilibrium is established:
2NOCl (g) 2NO (g) + Cl 2 (g)
2.0 mol of NOCl (g) were placed in a 1.0 dm3 container and allowed to reach equilibrium. At equilibrium 1.0 mol of NOCl (g) was present. What is the value of Kc?
24.
A.
0.50
B.
1.0
C.
1.5
D.
2.0
In which equilibria are the conjugate acid–base pairs correctly labelled?
I.
CO32– (aq) + H 2O (l) HCO3 – (aq) + OH – (aq)
Base 1
II.
Base 2
Acid 2
Acid 1
Base 2
NH 4 + (aq) + H 2O (l) H 3O + (aq) + NH 3 (aq)
Acid 1
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
2213-6107
Acid 1
HCO3 – (aq) + H 2O (l) H 2CO3 (aq) + OH – (aq)
Base 1
III.
Acid 2
Base 2
Acid 2
Base 1
– 13 –
25.
26.
M13/4/CHEMI/HPM/ENG/TZ1/XX
A solution of acid HX has a pH = 1 and a solution of acid HY has a pH = 3. Which statement must
be correct?
A.
HX is a stronger acid than HY.
B.
HY is a stronger acid than HX.
C.
The [H+] in the solution of HX is 100 times greater than the [H+] in the solution of HY.
D.
The [H+] in the solution of HY is 100 times greater than the [H+] in the solution of HX.
The values of Kw , the ionic product constant of water, are:
Kw
6.4 ×10–15
1.0 ×10–14
T / °C
18
25
Which statements are correct?
I.
The [OH–] in water is less than the [H+] at 18 °C .
II.
The ionization of water is an endothermic process.
III.
The pH of water is lower at 25 °C than at 18 °C .
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
2213-6107
Turn over
– 14 –
27.
28.
M13/4/CHEMI/HPM/ENG/TZ1/XX
For which equilibrium can an expression for a base dissociation constant, Kb , for the forward reaction
be written?
A.
NH 3 + H 3O + NH 4 + + H 2O
B.
F− + H 2O HF + OH –
C.
NH 4 + + OH – NH 3 + H 2O
D.
HF + OH – H 2O + F –
Which of the following mixtures, in an aqueous solution, will produce a buffer solution?
I.
50 cm3 of 0.1 mol dm–3 CH3COONa and 50 cm3 of 0.1 mol dm–3 CH3COOH
II.
50 cm3 of 0.1 mol dm–3 NH3 and 50 cm3 of 0.1 mol dm–3 NH4Cl
III.
50 cm3 of 0.1 mol dm–3 NaOH and 50 cm3 of 0.2 mol dm–3 CH3COOH
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
2213-6107
– 15 –
29.
M13/4/CHEMI/HPM/ENG/TZ1/XX
The colours of three indicators are shown in the table below.
Indicator
Colour at
low pH
Colour at
high pH
pH range at which colour
change takes place
methyl orange
red
yellow
3.2– 4.4
bromothymol blue
yellow
blue
6.0 –7.6
phenolphthalein
colourless
pink
8.2–10.0
Equal volumes of these three indicators were mixed and the mixture was added to a solution of
pH = 5.0. What colour would be seen?
30.
31.
A.
Yellow
B.
Orange
C.
Green
D.
Blue
Which statement is correct about a reducing agent?
A.
It is reduced by gaining electrons.
B.
It is oxidized by gaining electrons.
C.
It is oxidized by losing electrons.
D.
It is reduced by losing electrons.
An aqueous solution of a metal salt is electrolysed. Which factor will have no effect on the mass of
the metal deposited on the negative electrode (cathode), if all other variables remain constant?
A.
Size of metal ion
B.
Relative atomic mass of metal
C.
Current
D.
Charge on metal ion
2213-6107
Turn over
– 16 –
32.
33.
M13/4/CHEMI/HPM/ENG/TZ1/XX
Which are correct statements about a voltaic cell?
I.
A spontaneous redox reaction occurs which converts chemical energy to electrical energy.
II.
Oxidation occurs at the negative electrode (anode).
III.
Electricity is conducted by the movement of electrons through the salt bridge.
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
The standard electrode potentials of some half-reactions are given below.
Sn 4+ (aq) + 2e – Sn 2+ (aq)
1
2
I 2 (s) + e – I – (aq)
Fe3+ (aq) + e – Fe 2+ (aq)
E Ö = + 0.15 V
E Ö = + 0.54 V
E Ö = + 0.77 V
Which of the following reactions will occur spontaneously?
A.
Iodine reduces Fe3+ to Fe2+
B.
Iodine reduces Sn4+ to Sn2+
C.
Iodine oxidizes Fe2+ to Fe3+
D.
Iodine oxidizes Sn2+ to Sn4+
2213-6107
– 17 –
34.
M13/4/CHEMI/HPM/ENG/TZ1/XX
What is the name of the following compound applying IUPAC rules?
H
C
H
H
H
C
C
H
H
35.
cis-4-methylhex-2-ene
B.
cis-4-ethylpent-2-ene
C.
trans-4-methylhex-2-ene
D.
trans-4-ethylpent-2-ene
C
C
C
H
A.
H
C
H
H
H
H
H
H
Which steps are involved in the free-radical mechanism of the bromination of ethane in the presence
of ultraviolet radiation?
I.
C2 H 6 + Br i → C2 H 5 i + HBr
II.
C2 H 5 i + Br2 → C2 H 5 Br + Br i
III.
C2 H 5 i + Br i → C2 H 5 Br
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
2213-6107
Turn over
– 18 –
36.
37.
38.
M13/4/CHEMI/HPM/ENG/TZ1/XX
Which substance can be polymerized to produce the polymer below?
A.
But-1-ene
B.
But-2-ene
C.
Propene
D.
2-methylpropene
CH3 H
H
H
CH3 H
H
H
C
C
C
C
C
C
C
C
H
H
CH3 H
H
H
CH3 H
Which factors affect the rate of nucleophilic substitution in halogenoalkanes?
I.
The nature of the attacking nucleophile
II.
The identity of the halogen
III.
The structure of the halogenoalkane
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
Which molecule exhibits optical isomerism?
A.
3-chloropentane
B.
2-chlorobutane
C.
1,3-dichloropropane
D.
2-chloro-2-methylpropane
2213-6107
– 19 –
39.
40.
M13/4/CHEMI/HPM/ENG/TZ1/XX
What is a use of the organic product formed when an alcohol and a carboxylic acid react together?
A.
Pesticide
B.
Lubricant
C.
Flavourings in food
D.
Fertilizer
Which would be the best method to decrease the random uncertainty of a measurement in an
acid–base titration?
A.
Ensure your eye is at the same height as the meniscus when reading the burette.
B.
Use a different indicator for the titration.
C.
Use a different burette.
D.
Repeat the titration.
2213-6107
M13/4/CHEMI/HPM/ENG/TZ1/XX/M
MARKSCHEME
May 2013
CHEMISTRY
Higher Level
Paper 1
2 pages
–2–
M13/4/CHEMI/HPM/ENG/TZ1/XX/M
1.
C
16.
A
31.
A
46.
–
2.
D
17.
A
32.
A
47.
–
3.
D
18.
B
33.
D
48.
–
4.
B
19.
D
34.
C
49.
–
5.
C
20.
A
35.
D
50.
–
6.
A
21.
B
36.
C
51.
–
7.
B
22.
B
37.
D
52.
–
8.
C
23.
A
38.
B
53.
–
9.
A
24.
D
39.
C
54.
–
10.
C
25.
C
40.
D
55.
–
11.
A
26.
C
41.
–
56.
–
12.
D
27.
B
42.
–
57.
–
13.
B
28.
D
43.
–
58.
–
14.
A
29.
A
44.
–
59.
–
15.
B
30.
C
45.
–
60.
–
M13/4/CHEMI/HPM/ENG/TZ2/XX
22136113
CHEMISTRY
HIGHER LEVEL
PAPER 1
Thursday 16 May 2013 (afternoon)
1 hour
INSTRUCTIONS TO CANDIDATES
• Do not open this examination paper until instructed to do so.
• Answer all the questions.
• For each question, choose the answer you consider to be the best and indicate your choice on
the answer sheet provided.
• The periodic table is provided for reference on page 2 of this examination paper.
• The maximum mark for this examination paper is [40 marks].
2213-6113
17 pages
© International Baccalaureate Organization 2013
2213-6113
23
V
50.94
87
Fr
(223)
88
Ra
(226)
‡
†
89 ‡
Ac
(227)
90
Th
232.04
58
Ce
140.12
91
Pa
231.04
59
Pr
140.91
73
Ta
180.95
38
Sr
87.62
37
Rb
85.47
22
Ti
47.90
56
57 †
72
55
Ba
La
Cs
Hf
132.91 137.34 138.91 178.49
20
Ca
40.08
19
K
39.10
41
Nb
92.91
39
Y
88.91
12
Mg
24.31
11
Na
22.99
92
U
238.03
60
Nd
144.24
74
W
183.85
42
Mo
95.94
24
Cr
52.00
Relative atomic mass
Element
Atomic number
40
Zr
91.22
21
Sc
44.96
4
Be
9.01
2
3
Li
6.94
1
H
1.01
1
30
Zn
65.37
93
Np
(237)
94
Pu
(242)
95
Am
(243)
96
Cm
(247)
97
Bk
(247)
98
Cf
(251)
61
66
62
63
64
65
Pm
Dy
Sm
Tb
Eu
Gd
146.92 150.35 151.96 157.25 158.92 162.50
75
80
76
77
78
79
Re
Os
Pt
Au
Hg
Ir
186.21 190.21 192.22 195.09 196.97 200.59
48
44
45
46
47
Cd
Ru
Rh
Pd
Ag
101.07 102.91 106.42 107.87 112.40
29
Cu
63.55
43
Tc
98.91
28
Ni
58.71
26
Fe
55.85
25
Mn
54.94
27
Co
58.93
The Periodic Table
50
Sn
118.69
32
Ge
72.59
14
Si
28.09
6
C
12.01
4
99
Es
(254)
100
Fm
(257)
67
68
Ho
Er
164.93 167.26
81
82
Tl
Pb
204.37 207.19
49
In
114.82
31
Ga
69.72
13
Al
26.98
5
B
10.81
3
101
Md
(258)
69
Tm
168.93
83
Bi
208.98
51
Sb
121.75
33
As
74.92
15
P
30.97
7
N
14.01
5
35
Br
79.90
17
Cl
35.45
9
F
19.00
7
85
At
(210)
102
No
(259)
103
Lr
(260)
70
71
Lu
Yb
173.04 174.97
84
Po
(210)
52
53
Te
I
127.60 126.90
34
Se
78.96
16
S
32.06
8
O
16.00
6
86
Rn
(222)
54
Xe
131.30
36
Kr
83.80
18
Ar
39.95
10
Ne
20.18
2
He
4.00
0
–2–
M13/4/CHEMI/HPM/ENG/TZ2/XX
–3–
1.
2.
M13/4/CHEMI/HPM/ENG/TZ2/XX
How many atoms are present in 0.10 mol of PtCl2 (NH3)2?
A.
6.0 ×1022
B.
3.0 ×1023
C.
6.6 ×1023
D.
6.6 ×1024
What mass of carbon dioxide, CO2 (g), in g, is produced when 5.0 g of calcium carbonate, CaCO3 (s),
reacts completely with hydrochloric acid, HCl (aq)?
CaCO3 (s) + 2HCl (aq) → CaCl2 (aq) + H 2 O (l) + CO 2 (g)
3.
A.
0.050
B.
2.2
C.
4.4
D.
5.0
The volume occupied by one mole of an ideal gas at 273 K and 1.01×105 Pa is 22.4 dm3 mol–1.
What volume of hydrogen, in dm3, is produced when excess magnesium ribbon reacts with 100 cm3
of 2.00 mol dm–3 hydrochloric acid?
Mg (s) + 2HCl (aq) → MgCl2 (aq) + H 2 (g)
A.
0.100
B.
2.24
C.
4.48
D.
22.4
2213-6113
Turn over
–4–
4.
5.
6.
M13/4/CHEMI/HPM/ENG/TZ2/XX
Which is the correct order of the stages of operation in the mass spectrometer?
A.
vaporization, ionization, acceleration, deflection, detection
B.
vaporization, ionization, detection, deflection, acceleration
C.
ionization, vaporization, acceleration, deflection, detection
D.
ionization, deflection, acceleration, detection, vaporization
Which species has the electron configuration of 1s2 2s2 2p6 3s2 3p6 3d8?
A.
Ni
B.
Ni2+
C.
Fe
D.
Cu2+
Element X is in group 5 and period 4 of the periodic table. Which statement is correct?
A.
X has 5 occupied energy levels.
B.
X can form ions with 3– charge.
C.
X is a transition element.
D.
X has 4 valence electrons.
2213-6113
–5–
7.
8.
9.
M13/4/CHEMI/HPM/ENG/TZ2/XX
Which statements are correct for the alkali metals Li to Cs?
I.
Melting point increases
II.
First ionization energy decreases
III.
Ionic radius increases
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
Which statements about [Ag(NH3)2]+ are correct?
I.
NH3 forms a dative covalent (co-ordinate) bond with Ag+.
II.
The formation of the bond between NH3 and Ag+ is an example of a Lewis acid–base
reaction.
III.
Ag+ is the ligand in this complex ion.
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
Which is the best description of a metallic bond?
A.
Electrostatic attraction between oppositely charged ions
B.
Electrostatic attraction between a pair of electrons and positively charged nuclei
C.
Electrostatic attraction between a lattice of positive ions and delocalized electrons
D.
Electrostatic attraction for a bonding pair of electrons which have been supplied by one of
the atoms
2213-6113
Turn over
–6–
10.
11.
M13/4/CHEMI/HPM/ENG/TZ2/XX
Which statements about the structure and bonding of silicon dioxide are correct?
Structure
Bonding
A.
Silicon dioxide forms a giant covalent
network.
Each oxygen atom is covalently bonded
to two silicon atoms.
B.
Silicon dioxide molecules are V-shaped
or bent.
Each silicon atom is covalently bonded to
two oxygen atoms.
C.
Silicon dioxide molecules are linear.
A double covalent bond exists between
silicon and oxygen atoms.
D.
Silicon dioxide forms a giant covalent
network.
Each oxygen atom is covalently bonded
to four silicon atoms.
Which series shows increasing boiling points?
A.
CH3CH2CH3 < CH3CH2OH < CH3CHO
B.
CH3CHO < CH3CH2CH3 < CH3CH2OH
C.
CH3CH2OH < CH3CHO < CH3CH2CH3
D.
CH3CH2CH3 < CH3CHO < CH3CH2OH
2213-6113
M13/4/CHEMI/HPM/ENG/TZ2/XX
–7–
12.
How many sigma (σ) and pi (π) bonds are there in the following molecule?
H
H
H
H
C
C
C
H
13.
14.
σ bonds
π bonds
A.
9
2
B.
9
4
C.
11
2
D.
11
4
O
C
O
H
Which species have delocalized π electrons?
I.
CH3COCH3
II.
NO2–
III.
CO32–
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
The specific heat capacity of aluminium is 0.900 J g–1 K–1. What is the heat energy change, in J,
when 10.0 g of aluminium is heated and its temperature increases from 15.0 °C to 35.0 °C ?
A.
+180
B.
+315
C.
+1800
D.
+2637
2213-6113
Turn over
–8–
15.
M13/4/CHEMI/HPM/ENG/TZ2/XX
Enthalpy changes of reaction are provided for the following reactions.
2C (s) + 2H 2 (g) → C2 H 4 (g)
2C (s) + 3H 2 (g) → C 2 H 6 (g)
∆H Ö = +52 kJ mol−1
∆H Ö = −85 kJ mol−1
What is the enthalpy change, in kJ mol−1, for the reaction between ethene and hydrogen?
C2 H 4 (g) + H 2 (g) → C 2 H 6 (g)
16.
17.
A.
–137
B.
–33
C.
+33
D.
+137
Which reaction has an enthalpy change equal to the standard enthalpy change of combustion?
A.
C3 H8 (g) + 5O 2 (g) → 3CO 2 (g) + 4H 2 O (g)
B.
C3 H8 (g) + 5O 2 (g) → 3CO 2 (g) + 4H 2 O (l)
C.
2C4 H10 (g) + 13O 2 (g) → 8CO 2 (g) + 10H 2 O (l)
D.
C5 H12 (g) + 8O 2 (g) → 5CO 2 (g) + 6H 2 O (g)
Which reactions/processes have a positive entropy change, ∆S Ö ?
I.
NaCl (s) → NaCl (aq)
II.
Na 2 CO3 (s) + 2HCl (aq) → CO 2 (g) + 2NaCl (aq) + H 2 O (l)
III.
AgNO3 (aq) + NaCl (aq) → AgCl (s) + NaNO3 (aq)
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
2213-6113
–9–
18.
19.
M13/4/CHEMI/HPM/ENG/TZ2/XX
Which compound has the most positive lattice enthalpy of dissociation?
A.
NaCl
B.
NaBr
C.
MgCl2
D.
MgBr2
Which statements explain the increase in the rate of a reaction when the temperature is increased?
I.
More particles have energy greater than the activation energy.
II.
The frequency of collisions increases.
III.
The activation energy decreases.
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
2213-6113
Turn over
– 10 –
20.
M13/4/CHEMI/HPM/ENG/TZ2/XX
Experimental data shows that a reaction in which Y is a reactant is first order with respect to Y. Which graph shows this first-order relationship?
A.
B.
[Y]
[Y]
1
0.5
1
0.5
Time
C.
D.
[Y]
[Y]
1
0.5
1
0.5
Time
21.
Time
Time
Which statement about a reaction best describes the relationship between the temperature, T,
and the rate constant, k ?
A.
As T increases, k decreases linearly.
B.
As T increases, k decreases non-linearly.
C.
As T increases, k increases linearly.
D.
As T increases, k increases non-linearly.
2213-6113
– 11 –
22.
M13/4/CHEMI/HPM/ENG/TZ2/XX
Carbon monoxide and nitrogen dioxide react to form carbon dioxide and nitrogen monoxide
according to the following equation.
CO (g) + NO 2 (g) → CO 2 (g) + NO (g)
The reaction occurs in a series of steps. The equation for the rate-determining step is given below.
2NO 2 (g) → NO3 (g) + NO (g)
What is the rate expression for this reaction?
23.
A.
rate = k [CO (g)] [NO 2 (g)]
B.
rate = k [NO 2 (g)]2
C.
rate = k [NO3 (g)] [NO (g)]
D.
rate = k [CO 2 (g)] [NO (g)]
Hydrogen and iodine react in a closed vessel to form hydrogen iodide.
H 2 (g) + I 2 (g) 2HI (g)
At 350 °C
At 445 °C
K c = 60
K c = 47
Which statement describes and explains the conditions that favour the formation of hydrogen iodide?
A.
Increased temperature as the forward reaction is exothermic, and increased pressure as there are
two gaseous reactants and only one gaseous product
B.
Increased temperature as the forward reaction is endothermic, and pressure has no effect as
there are equal amounts, in mol, of gaseous reactants and products
C.
Decreased temperature as the forward reaction is exothermic, and decreased pressure as there
are two moles of gaseous product but only one mole of each gaseous reactant
D.
Decreased temperature as the forward reaction is exothermic, and pressure has no effect as there
are equal amounts, in mol, of gaseous reactants and products
2213-6113
Turn over
– 12 –
24.
25.
26.
27.
M13/4/CHEMI/HPM/ENG/TZ2/XX
Which change would increase the vapour pressure of a liquid in equilibrium with its vapour in a
sealed container?
A.
Increasing the temperature while keeping the surface area of the liquid constant
B.
Increasing the surface area of the liquid while maintaining a constant temperature
C.
Adding more liquid at constant temperature
D.
Adding more of the vapour at constant temperature
Which compound has the highest enthalpy of vaporization?
A.
CO2
B.
NH3
C.
H2S
D.
H2O
Which of the following is an example of a Lewis acid–base reaction, but not a Brønsted–Lowry
acid–base reaction?
A.
2CrO 4 2− (aq) + 2H + (aq) → Cr2 O7 2− (aq) + H 2 O (l)
B.
Co(H 2 O)6 2+ (aq) + 4HCl (aq) → CoCl4 2− (aq) + 4H + (aq) + 6H 2 O (l)
C.
NH 3 (aq) + H + (aq) → NH 4 + (aq)
D.
CH 3COO − (aq) + H 2 O (l) → CH 3COOH (aq) + OH − (aq)
Which list contains only strong bases?
A.
ammonia, sodium hydroxide, ethylamine
B.
potassium hydroxide, ammonia, sodium hydroxide
C.
lithium hydroxide, potassium hydroxide, barium hydroxide
D.
ammonia, ethylamine, barium hydroxide
2213-6113
– 13 –
28.
29.
M13/4/CHEMI/HPM/ENG/TZ2/XX
The pKb value of ammonia is 4.75 at 298 K. What is the pKa value of the ammonium ion?
A.
10−14
4.75
B.
14.00
4.75
C.
14.00 − 4.75
D.
10−14
10− 4.75
The Ka values of four weak acids W, X, Y and Z are listed below.
W
K a = 1.35 ×10−3
X
K a = 4.47 ×10−2
Y
K a = 9.33 × 10−6
Z
K a = 1.47 ×10−5
What is the correct order of increasing strength as acids?
30.
A.
X<W<Z<Y
B.
W<Z<X<Y
C.
Y<X<Z<W
D.
Y<Z<W<X
Which is the oxidizing agent in the following reaction?
5SO 2 (g) + 2IO3− (aq) + 4H 2 O (l) → 5SO 4 2− (aq) + I 2 (aq) + 8H + (aq)
A.
SO2
B.
IO3–
C.
H2O
D.
SO42–
2213-6113
Turn over
– 14 –
31.
M13/4/CHEMI/HPM/ENG/TZ2/XX
The overall reaction in the voltaic cell below is:
Ni (s) + Pb 2+ (aq) → Ni 2+ (aq) + Pb (s)
voltmeter
V
salt bridge
nickel
solution containing Ni2+ (aq)
lead
solution containing Pb2+ (aq)
Which statement is correct for the nickel half-cell?
32.
A.
Nickel is the positive electrode (cathode) and is reduced.
B.
Nickel is the negative electrode (anode) and is reduced.
C.
Nickel is the positive electrode (cathode) and is oxidized.
D.
Nickel is the negative electrode (anode) and is oxidized.
Which statement is correct for electroplating an object with gold?
A.
The object must be the negative electrode (cathode).
B.
The negative electrode (cathode) must be gold.
C.
The object must be the positive electrode (anode).
D.
The gold electrode must be pure.
2213-6113
– 15 –
33.
34.
35.
M13/4/CHEMI/HPM/ENG/TZ2/XX
What are possible products of the incomplete combustion of propan-2-ol?
A.
carbon monoxide, hydrogen and carbon
B.
carbon dioxide, carbon and hydrogen
C.
carbon, carbon monoxide and water
D.
carbon dioxide and water only
Which equation represents a propagation step in the mechanism for the reaction between ethane,
C2H6 , and chlorine, Cl2 , in the presence of sunlight/UV?
A.
C2 H 6 + Cli → C2 H 5 i + HCl
B.
C2 H 6 + Cli → C2 H 5 Cl + Hi
C.
Cl2 → 2Cli
D.
C2 H 5 i + Cli → C2 H 5Cl
What is the name of CH3CH2CH2CN applying IUPAC rules?
A.
Butanamine
B.
Butanamide
C.
Propanenitrile
D.
Butanenitrile
2213-6113
Turn over
– 16 –
36.
M13/4/CHEMI/HPM/ENG/TZ2/XX
1-bromobutane, CH3CH2CH2CH2Br, can be converted to 1-aminopentane, CH3CH2CH2CH2CH2NH2,
in a two-step process.
I → CH CH CH CH CN
CH 3CH 2 CH 2 CH 2 Br 
3
2
2
2
II
CH 3CH 2 CH 2 CH 2 CN → CH 3CH 2 CH 2 CH 2 CH 2 NH 2
What are the reagents I and II?
I
37.
38.
II
A.
ammonia
hydrogen with nickel
B.
ammonia
hydrochloric acid
C.
potassium cyanide
ammonia
D.
potassium cyanide
hydrogen with nickel
Which halogenoalkane reacts the fastest with hydroxide ions in a nucleophilic substitution reaction?
A.
1-chlorobutane
B.
2-chloro-2-methylpropane
C.
1-iodobutane
D.
2-iodo-2-methylpropane
Ethylamine, CH3CH2NH2 , reacts with propanoic acid, CH3CH2COOH. Initially a salt is formed
which, when heated at 200 °C , can form an organic product. What is the structural formula of the
organic product?
A.
CH3CH2NHCOCH2CH3
B.
CH3CH2NHCOOCH2CH3
C.
CH3CH2COONHCH2CH3
D.
CH3CH2COOCH2CH3
2213-6113
– 17 –
39.
M13/4/CHEMI/HPM/ENG/TZ2/XX
Which structure is a geometric isomer of cis-1,2-dichlorocyclobutane?
A.
B.
H
H
Cl
H
H
Cl
H
H
H
D.
Cl
Cl
H
Cl
H
H
40.
Cl
H
H
H
Cl
H
H
H
H
H
H
C.
H
Cl
H
H
H
H
Using an accurate pH meter, the pH of lemonade was found to be 2.30. Some students deduced the
pH of the lemonade after titration with a 0.10 mol dm–3 sodium hydroxide solution. Their
determined values of pH were 2.4, 2.5, 2.4 and 2.4. What is the best description of the precision and
accuracy of these measurements?
Precision
Accuracy
A.
precise
inaccurate
B.
not precise
inaccurate
C.
precise
accurate
D.
not precise
accurate
2213-6113
M13/4/CHEMI/HPM/ENG/TZ2/XX/M
MARKSCHEME
May 2013
CHEMISTRY
Higher Level
Paper 1
2 pages
–2–
M13/4/CHEMI/HPM/ENG/TZ2/XX/M
1.
C
16.
B
31.
D
46.
–
2.
B
17.
A
32.
A
47.
–
3.
B
18.
C
33.
C
48.
–
4.
A
19.
A
34.
A
49.
–
5.
B
20.
C
35.
D
50.
–
6.
B
21.
D
36.
D
51.
–
7.
C
22.
B
37.
D
52.
–
8.
A
23.
D
38.
A
53.
–
9.
C
24.
A
39.
A
54.
–
10.
A
25.
D
40.
B
55.
–
11.
D
26.
B
41.
–
56.
–
12.
C
27.
C
42.
–
57.
–
13.
C
28.
C
43.
–
58.
–
14.
A
29.
D
44.
–
59.
–
15.
A
30.
B
45.
–
60.
–
M13/4/CHEMI/HP2/ENG/TZ1/XX
22136108
CHEMISTRY
HIGHER LEVEL
PAPER 2
Candidate session number
0
0
Thursday 16 May 2013 (afternoon)
Examination code
2
2 hours 15 minutes
2
1
3
–
6
1
0
8
INSTRUCTIONS TO CANDIDATES
•
•
•
•
•
•
•
•
Write your session number in the boxes above.
Do not open this examination paper until instructed to do so.
Section A: answer all questions.
Section B:answer two questions.
Write your answers in the boxes provided.
A calculator is required for this paper.
A clean copy of the Chemistry Data Booklet is required for this paper.
The maximum mark for this examination paper is [90 marks].
32 pages
© International Baccalaureate Organization 2013
0132
–2–
M13/4/CHEMI/HP2/ENG/TZ1/XX
SECTION A
Answer all questions. Write your answers in the boxes provided.
1.
A student decided to determine the molecular mass of a solid monoprotic acid, HA, by titrating a
solution of a known mass of the acid.
The following recordings were made.
Mass of bottle / g ± 0.001 g
Mass of bottle + acid HA / g ± 0.001 g
(a)
1.737
2.412
Calculate the mass of the acid and determine its absolute and percentage uncertainty.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
This known mass of acid, HA, was then dissolved in distilled water to form a 100.0 cm3
solution in a volumetric flask. A 25.0 cm3 sample of this solution reacted with 12.1 cm3 of
a 0.100 mol dm–3 NaOH solution. Calculate the molar mass of the acid.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
0232
–3–
M13/4/CHEMI/HP2/ENG/TZ1/XX
(Question 1 continued)
(c)
The percentage composition of HA is 70.56 % carbon, 23.50 % oxygen and 5.94 %
hydrogen. Determine its empirical formula.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (d)
[2]
Determine the molecular formula of HA.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (e)
A solution of HA is a weak acid. Distinguish between a weak acid and a strong acid.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
0332
–4–
M13/4/CHEMI/HP2/ENG/TZ1/XX
(Question 1 continued)
To investigate the effect of temperature on the effectiveness of a buffer solution, the student
placed 20.0 cm3 of the buffer solution in a water bath at 24 °C . He added small portions of
hydrochloric acid, stirring after each addition, until a total of 10 cm3 was added, and measured
the pH continuously during the addition. The procedure was repeated at different temperatures
and the results are shown in the following graph.
5.0
4.5
4.0
Key:
3.5
pH of solution
(f)
3.0
24 °C
35 °C
2.5
40 °C
50 °C
2.0
70 °C
1.5
1.0
0.5
0.0
0
5
10
Volume of HCl added / cm3
(This question continues on the following page)
0432
–5–
M13/4/CHEMI/HP2/ENG/TZ1/XX
(Question 1 continued)
(i)
State what is meant by a buffer solution.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
With reference to the graph on page 4, describe the effect of increasing temperature
on the effectiveness of the buffer solution.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
0532
–6–
Please do not write on this page.
Answers written on this page
will not be marked.
0632
M13/4/CHEMI/HP2/ENG/TZ1/XX
–7–
2.
M13/4/CHEMI/HP2/ENG/TZ1/XX
Table 8 of the Data Booklet shows the atomic and ionic radii of the elements.
(a)
[3]
Describe and explain the trend in atomic radius across period 3.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
A student formulates the following hypothesis: “If phosphorus were to form a positive
ion, P3+, its ionic radius would probably be between 110 × 10 –12 m and 212 × 10 –12 m.” [2]
Evaluate this hypothesis.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
0732
–8–
3.
M13/4/CHEMI/HP2/ENG/TZ1/XX
To determine the activation energy of a reaction, the rate of reaction was measured at different
temperatures. The rate constant, k , was determined and ln k was plotted against the inverse of the
temperature in Kelvin, T –1. The following graph was obtained.
T –1 / 10–2 K–1
0.00
0.0
1.0
2.0
3.0
4.0
5.0
6.0
– 0.50
–1.00
–1.50
–2.00
ln k
–2.50
–3.00
–3.50
– 4.00
– 4.50
–5.00
(a)
Define the term activation energy, Ea .
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
0832
–9–
M13/4/CHEMI/HP2/ENG/TZ1/XX
(Question 3 continued)
(b)
Use the graph on page 8 to determine the value of the activation energy, Ea , in kJ mol–1.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (c)
On the graph on page 8, sketch the line you would expect if a catalyst is added to
the reactants.
[1]
Turn over
0932
– 10 –
4.
M13/4/CHEMI/HP2/ENG/TZ1/XX
Ethanedioic acid (oxalic acid), (COOH)2 , reacts with acidified potassium permanganate solution,
KMnO4 , according to the following equation.
5(COOH) 2 (aq) + 2MnO 4 – (aq) + 6H + (aq) → 10CO 2 (g) + 2Mn 2+ (aq) + 8H 2O (l)
The reaction is a redox reaction.
(a)
Define oxidation in terms of electron transfer.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
Calculate the change in oxidation numbers of carbon and manganese.
[2]
Carbon:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Manganese:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (c)
[1]
Identify the oxidizing and reducing agents.
Oxidizing agent:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reducing agent:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
1032
– 11 –
M13/4/CHEMI/HP2/ENG/TZ1/XX
(Question 4 continued)
(d)
[1]
Deduce the half-equation involving ethanedioic acid.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (e)
(i)
The standard electrode potential for the half-equation involving ethanedioic acid is
E Ö = – 0.49 V. Using Table 14 of the Data Booklet, calculate the standard electrode
potential for the equation on page 10.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(ii)
[1]
Explain the sign of the calculated standard electrode potential.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(f)
Predict the sign of ëG Ö for this reaction.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
1132
– 12 –
5.
M13/4/CHEMI/HP2/ENG/TZ1/XX
The following diagram shows the three-dimensional structure of a molecule.
H
C
C
H
C
H
H
H
H
H
C
O
H
H
H
(a)
Apply IUPAC rules to state the name of this molecule.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
Deduce the structural formula of two isomers of the molecule above with the same
functional group.
[2]
(This question continues on the following page)
1232
– 13 –
M13/4/CHEMI/HP2/ENG/TZ1/XX
(Question 5 continued)
(c)
Some organic nitrogen compounds have economic importance.
(i)
[1]
Apply IUPAC rules to state the name of CH3CH2CH2NH2 .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Describe, using an equation, how CH3CH2CH2NH2 can be prepared from a nitrile.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) Some polymers can be produced by the reaction of amines and carboxylic acids.
Identify what type of reaction this is.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv) State one important feature monomers must have to be able to produce such
polymers.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (v)
[1]
Outline the economic importance of this type of polymer.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
1332
– 14 –
M13/4/CHEMI/HP2/ENG/TZ1/XX
SECTION B
Answer two questions. Write your answers in the boxes provided.
6.
The element boron has two naturally occurring isotopes, 10B and 11B.
(a)
(i)
Define the term isotopes of an element.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Calculate the percentage abundance of each isotope, given that the relative atomic
mass of B is 10.81.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
1432
– 15 –
M13/4/CHEMI/HP2/ENG/TZ1/XX
(Question 6 continued)
(b)
The percentage abundance of the isotopes of boron can be determined with a mass spectrometer. The diagram shows the operation of a mass spectrometer.
Q
R
S
B (g)
to vacuum
pump
(i)
(ii)
State the names of stages R and S.
[1]
R:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
S:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Identify the formula of the main ion formed in stage Q.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [1]
(iii) Identify the species that is used as the scale for the mass of the isotopes.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
1532
– 16 –
M13/4/CHEMI/HP2/ENG/TZ1/XX
(Question 6 continued)
(c)
Phosphorus forms two chlorides, PCl3 and PCl5.
Apply the Aufbau principle to state the full electron configuration for an atom
of phosphorus.
(i)
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
[2]
Deduce the Lewis structures for PCl3 and PCl5.
PCl3
PCl5
[4]
(iii) Predict the shapes and the bond angles in the two molecules.
PCl3
Shape
Bond angles
PCl5
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
1632
– 17 –
M13/4/CHEMI/HP2/ENG/TZ1/XX
(Question 6 continued)
[1]
(iv) Identify the type of hybridization present in PCl3.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (v)
[3]
Compare the melting points of PCl3 and PCl5 and explain the difference.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [1]
(vi) Describe, using an equation, the reaction of PCl5 with water.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
1732
– 18 –
M13/4/CHEMI/HP2/ENG/TZ1/XX
(Question 6 continued)
(d)
(i)
Define an acid according to the Lewis theory.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
State and explain the acid–base character of PCl3 according to the Lewis theory.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (e)
Explain the delocalization of π electrons using the O3 molecule as an example,
including two facts that support the delocalization.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1832
[4]
– 19 –
7.
(a)
M13/4/CHEMI/HP2/ENG/TZ1/XX
Bromine is a member of group 7, the halogens.
(i)
[3]
Explain the trend in reactivity of the halogens.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Deduce, using equations where appropriate, if bromine reacts with sodium chloride
solution and with sodium iodide solution.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
Iron is a transition metal.
(i)
[3]
Describe the bonding in metals and explain their malleability.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
1932
– 20 –
M13/4/CHEMI/HP2/ENG/TZ1/XX
(Question 7 continued)
(ii)
List three characteristic properties of transition elements.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) Identify the type of bonding between iron and cyanide in [Fe(CN)6]3–.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv) Deduce the oxidation number of iron in [Fe(CN)6]3–.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (v)
Draw the abbreviated orbital diagram for an iron atom using the arrow-in-box
notation to represent electrons.
[1]
(This question continues on the following page)
2032
– 21 –
M13/4/CHEMI/HP2/ENG/TZ1/XX
(Question 7 continued)
(vi) Draw the abbreviated orbital diagram for the iron ion in [Fe(CN)6]3– using the
arrow-in-box notation to represent electrons.
(c)
[1]
Freshly prepared iron(II) bromide can be electrolysed both in the liquid state and in aqueous
solution.
(i)
Describe, using a diagram, the essential components of an electrolytic cell.
[3]
(This question continues on the following page)
Turn over
2132
– 22 –
M13/4/CHEMI/HP2/ENG/TZ1/XX
(Question 7 continued)
(ii)
Describe the two ways in which current is conducted in an electrolytic cell.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) Predict and explain the products of electrolysis of a dilute iron(II) bromide solution.
[4]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
2232
– 23 –
M13/4/CHEMI/HP2/ENG/TZ1/XX
(Question 7 continued)
(iv) Identify another product that is formed if the solution of iron(II) bromide is
concentrated.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (v)
[1]
Explain why this other product is formed.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
2332
– 24 –
8.
M13/4/CHEMI/HP2/ENG/TZ1/XX
To determine the enthalpy change of combustion of methanol, CH3OH, 0.230 g of methanol was
combusted in a spirit burner. The heat released increased the temperature of 50.0 cm3 of water from
24.5 °C to 45.8 °C .
(a)
(i)
Calculate the enthalpy change of combustion of methanol.
[4]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Using the theoretical value in Table 12 of the Data Booklet, discuss the experimental
result, including one improvement that could be made.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
2432
– 25 –
M13/4/CHEMI/HP2/ENG/TZ1/XX
(Question 8 continued)
(b)
Methanol can be produced according to the following equation.
CO (g) + 2H 2 (g) → CH 3OH (l)
(i)
Calculate the standard enthalpy change of this reaction, using the values of enthalpy
of combustion in Table 12 of the Data Booklet.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Calculate the standard entropy change for this reaction, ëS Ö , using Table 11 of the
Data Booklet and given:
S Ö (CO) = 198 J K–1 mol–1 and S Ö (H2) = 131 J K–1 mol–1.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) Calculate, stating units, the standard free energy change for this reaction, ëG Ö,
at 298 K.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
2532
– 26 –
M13/4/CHEMI/HP2/ENG/TZ1/XX
(Question 8 continued)
(iv) Predict, with a reason, the effect of an increase in temperature on the spontaneity of
this reaction.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (c)
The manufacture of gaseous methanol from CO and H2 involves an equilibrium reaction.
CO (g) + 2H 2 (g) CH 3OH (g)
(i)
∆H Ö < 0
Outline the characteristics of a chemical equilibrium.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Deduce the equilibrium constant expression, Kc , for this reaction.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
2632
– 27 –
M13/4/CHEMI/HP2/ENG/TZ1/XX
(Question 8 continued)
(iii) 1.00 mol of CH3OH is placed in a closed container of volume 1.00 dm3 until
equilibrium is reached with CO and H2 . At equilibrium 0.492 mol of CH3OH
are present. Calculate Kc .
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (d)
State and explain the effect of the following changes on the equilibrium position of the reaction
in part (c).
(i)
[2]
Increase in temperature.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
[2]
Increase in pressure.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
2732
– 28 –
9.
M13/4/CHEMI/HP2/ENG/TZ1/XX
But-2-ene belongs to the homologous series of the alkenes.
(a)
(i)
Outline three features of a homologous series.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Describe a test to distinguish but-2-ene from butane, including what is observed in
each case.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) 2-bromobutane can be produced from but-2-ene. State the equation of this reaction
using structural formulas.
[1]
(This question continues on the following page)
2832
– 29 –
M13/4/CHEMI/HP2/ENG/TZ1/XX
(Question 9 continued)
(iv) State what is meant by the term stereoisomers.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (v)
[2]
Explain the existence of geometrical isomerism in but-2-ene.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
A bromoalkane, C4H9Br, reacts with a warm aqueous sodium hydroxide solution, NaOH.
(i)
[1]
State the equation for the reaction of C4H9Br with NaOH.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Suggest what would happen to the pH of the solution as the reaction proceeds.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
2932
– 30 –
M13/4/CHEMI/HP2/ENG/TZ1/XX
(Question 9 continued)
(c)
The time taken to produce a certain amount of product using different initial concentrations
of C4H9Br and NaOH is measured. The results are shown in the following table.
Reaction [C4H9Br] / 10–2 mol dm–3 [NaOH] / 10–3 mol dm–3
A
1.0
2.0
B
2.0
2.0
C
2.0
4.0
(i)
t/s
46
23
23
Deduce the order of reaction with respect to C4H9Br and NaOH, using the
data above.
[3]
C4H9Br:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . NaOH:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
[1]
Deduce the rate expression.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) Based on the rate expression obtained in (c) (ii) state the units of the rate
constant, k.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
3032
– 31 –
M13/4/CHEMI/HP2/ENG/TZ1/XX
(Question 9 continued)
[2]
(iv) Deduce whether C4H9Br is a primary or tertiary halogenoalkane.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (v)
Determine the structural formula of C4H9Br.
[1]
(This question continues on the following page)
Turn over
3132
– 32 –
M13/4/CHEMI/HP2/ENG/TZ1/XX
(Question 9 continued)
(d)
(i)
Explain the mechanism for the reaction in (c), of C4H9Br with NaOH, using curly
arrows to represent the movement of electron pairs.
(ii)
Halogenalkanes can react with NaOH via SN1 and SN2 type mechanisms. Explain why C4H9Br reacts via the mechanism described in (d) (i).
[1]
[4]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) Identify the rate-determining step of this mechanism.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3232
[1]
M13/4/CHEMI/HP2/ENG/TZ1/XX/M
MARKSCHEME
May 2013
CHEMISTRY
Higher Level
Paper 2
17 pages
–2–
M13/4/CHEMI/HP2/ENG/TZ1/XX/M
This markscheme is confidential and for the exclusive use of
examiners in this examination session.
It is the property of the International Baccalaureate and must not
be reproduced or distributed to any other person without the
authorization of the IB Assessment Centre.
–3–
M13/4/CHEMI/HP2/ENG/TZ1/XX/M
Subject Details: Chemistry HL Paper 2 Markscheme
Mark Allocation
Candidates are required to answer ALL questions in Section A [40 marks] and TWO questions in
Section B [2 x 25 marks]. Maximum total = [90 marks].
1.
A markscheme often has more marking points than the total allows. This is intentional.
2.
Each marking point has a separate line and the end is shown by means of a semicolon (;).
3.
An alternative answer or wording is indicated in the markscheme by a slash (/). Either wording can
be accepted.
4.
Words in brackets ( ) in the markscheme are not necessary to gain the mark.
5.
Words that are underlined are essential for the mark.
6.
The order of marking points does not have to be as in the markscheme, unless stated otherwise.
7.
If the candidate’s answer has the same “meaning” or can be clearly interpreted as being of
equivalent significance, detail and validity as that in the markscheme then award the mark.
Where this point is considered to be particularly relevant in a question it is emphasized by
OWTTE (or words to that effect).
8.
Remember that many candidates are writing in a second language. Effective communication is more
important than grammatical accuracy.
9.
Occasionally, a part of a question may require an answer that is required for subsequent
marking points. If an error is made in the first marking point then it should be penalized. However,
if the incorrect answer is used correctly in subsequent marking points then follow through marks
should be awarded. When marking, indicate this by adding ECF (error carried forward) on the
script.
10.
Do not penalize candidates for errors in units or significant figures, unless it is specifically referred
to in the markscheme.
11.
If a question specifically asks for the name of a substance, do not award a mark for a correct
formula unless directed otherwise in the markscheme. Similarly if the formula is specifically asked
for, unless directed otherwise in the markscheme, do not award a mark for a correct name.
12.
If a question asks for an equation for a reaction, a balanced symbol equation is usually expected; do
not award a mark for a word equation or an unbalanced equation unless directed otherwise in the
markscheme.
13.
Ignore missing or incorrect state symbols in an equation unless directed otherwise in the
markscheme.
–4–
M13/4/CHEMI/HP2/ENG/TZ1/XX/M
SECTION A
1.
(a)
0.675 (g) ± 0.002 (g);
Percentage uncertainty: 0.3 %;
[2]
Accept answers correct to one, two or three significant figures for percentage uncertainty.
(b)
In 25.0 cm3: nHA = 1.21×10−3 (mol) ;
In 100 cm3: nHA = 4.84 ×10−3 (mol) ;
0.675 

M=
= 139 (g mol –1 ) ;
−3 
 4.84 × 10 
Award [3] for correct final answer.
Accept suitable alternative methods.
(c)
(d)
(e)
(f)
 70.56 
 23.50 
nC: 
=  5.88 and nO: 
=  1.47 and nH:
 12.01 
 16

C4H4O;
Award [2] for correct final answer.
Accept answers using integer values of molar mass.
(a)
(b)
 5.94

 1.01

=  5.88;


 139
M
=
=2;

 Mass of C 4 H 4 O  68.08
C8 H 8 O 2 ;
Award [2] for correct final answer.
weak acids partially dissociated/ionized and strong acids completely dissociated/
ionized (in solution/water) / OWTTE;
(i)
[2]
[2]
[1]
solution which resists change in pH / changes pH slightly / keeps pH constant /
OWTTE;
when small amounts of acid or base are added;
[2]
less effective at higher temperatures / more effective between 24 °C and 40 °C
than > 40 °C ;
pH changes more if the same volume of acid is added at high(er) temperature /
OWTTE;
[2]
decreases (from left to right/across period 3);
same number of shells/energy levels / shielding remains the same;
number of protons/nuclear charge increases so attraction of nucleus on outer electrons
increases / OWTTE;
[3]
hypothesis is wrong since ionic radius should be smaller than atomic
radius/ 110 ×10−12 m ;
greater attraction of the nucleus on outer electrons / effective charge of nucleus
greater / repulsive forces between electrons smaller;
[2]
(ii)
2.
[3]
–5–
3.
(a)
(b)
4.
M13/4/CHEMI/HP2/ENG/TZ1/XX/M
minimum energy needed to react/start a reaction / energy difference between
reactants and transition state;
[1]
gradient of the line: –63;
Accept –60 to –65.
Ea (= − R × gradient) = 0.52 (kJ mol−1 ) ;
Accept 0.50 to 0.54.
[2]
(c)
gradient of the line less steep (less negative);
Accept any position as long as gradient less steep.
[1]
(a)
loss of electrons;
[1]
(b)
Carbon:
III to IV / +3 to +4 / (+)1;
Manganese:
VII to II / +7 to +2 / –5;
Penalize incorrect notation such as 3+ once only in all the paper.
[2]
(c)
Oxidizing agent: MnO4– and Reducing agent: (COOH)2;
Accept correct names instead of formulas.
Do not accept Mn and C.
[1]
(d)
(COOH)2  2CO 2 + 2H + + 2e – ;
Accept either → or  .
Allow equation times 5.
Allow e instead of e–.
[1]
(e)
(i)
(ii)
(f)
MnO 4 − (aq) + 8H + (aq) + 5e −  Mn 2+ (aq) + 4H 2 O (l) E Ö = 1.51V ;
ëE Ö (= 1.51 + 0.49) = 2.00 V ;
First mark may be implied in the calculation.
Allow e instead of e–.
Accept either → or  .
[2]
positive sign, spontaneous reaction;
Allow ECF from (e) (i).
[1]
negative/< 0;
Do not allow ECF. This mark is independent of the answer in (e)(ii).
[1]
–6–
5.
M13/4/CHEMI/HP2/ENG/TZ1/XX/M
(a)
butan-2-ol/2-butanol;
(b)
CH3CH2CH2CH2OH;
(CH3)2CHCH2OH;
[2 max]
(CH3)3COH;
Accept condensed or full structural formulas.
Penalise missing H atoms or incorrect bonds (such as C–HO, C–H2C) once only in
the whole paper.
(c)
(i)
1-aminopropane/propylamine/1-propanamine;
[1]
(ii)
CH 3CH 2CN + 2H 2 → CH 3CH 2CH 2 NH 2 ;
Accept condensed or full structural formulas.
[1]
(iii) condensation (polymerization) / polycondensation;
[1]
(iv) two reactive/functional groups;
[1]
(v)
[1]
production of nylon/clothes/carpets/ropes/Kevlar;
Accept other uses of nylon.
[1]
–7–
M13/4/CHEMI/HP2/ENG/TZ1/XX/M
SECTION B
6.
(a)
(i)
(ii)
atoms of the same element/with the same number of protons/with same atomic
number but different number of neutrons/mass number/mass;
10 x + 11(1 − x) = 10.81, x = 0.19 ;
Accept similar method.
10
(b)
(c)
[1]
B: 19% and 11B: 81%;
[2]
(i)
R: acceleration and S: deflection;
[1]
(ii)
B+;
[1]
(iii)
12
C/carbon-12;
[1]
(i)
1s22s22p63s23p3;
[1]
(ii)
PCl3
Cl
P
PCl5
Cl
;
;
Cl
[2]
Penalize missing lone pairs on chlorine only once.
Accept any combination of lines, dots or crosses to represent electron pairs.
(iii)
PCl3
Shape
trigonal/triangular pyramidal;
Bond angles any angle between 99 and 108 ;
PCl5
trigonal/triangular bipyramidal;
90 and 120 ; ignore 180
[4]
Shape and bond angle must be consistent with the number of electron domains
given in the diagram in (ii).
(iv) sp3 (hybridization);
(v)
(vi)
PCl5 has higher melting point than PCl3;
PCl5 has stronger intermolecular/London/dispersion/van der Waals’ forces;
(because of) more electrons/greater mass;
Accept the opposite argument for PCl3.
Award [1 max] for answers suggesting PCl3 has higher melting point because
it is polar and PCl5 is not.
PCl5 (s) + 4H 2O (l) → H 3PO 4 (aq) + 5HCl (aq) ;
Ignore state symbols.
[1]
[3]
[1]
–8–
(d)
(e)
M13/4/CHEMI/HP2/ENG/TZ1/XX/M
(i)
electron pair acceptor;
[1]
(ii)
Lewis base;
has non-bonding/lone pair of electrons;
No ECF from (i).
[2]
overlap of p orbitals / p electrons of double/π bond and non-bonding/lone pair on
oxygen interact / OWTTE;
π electrons not localized / different resonance structures possible /
;
both bonds/O–O and O=O have equal length / OWTTE;
both bonds/O–O and O=O have equal bond energy / OWTTE;
[4]
–9–
7.
(a)
(i)
(ii)
(b)
(i)
M13/4/CHEMI/HP2/ENG/TZ1/XX/M
reactivity decreases down group;
as atomic radius increases / more electron shells;
attraction of nucleus on electrons decreases / electron affinity decreases;
Accept opposite argument for “up the group”.
[3]
no reaction with NaCl;
Br2 (aq) + 2NaI (aq) → 2NaBr (aq) + I 2 (aq) ;
Accept ionic equation.
Ignore state symbols.
[2]
(electrostatic attraction between a) lattice of positive ions/cations and
delocalized/sea of electrons;
Accept suitable diagram.
atoms/ions/layers (of positive ions) can slide over each other / OWTTE;
without change in the bonding forces / OWTTE;
(ii)
[3]
variable oxidation numbers/valency
form complex (ions)
form coloured compounds/ions
catalytic (behaviour)
Award [2] for any three, [1] for any two.
[2]
(iii) dative (covalent)/coordinate;
[1]
(iv) III / +3;
Penalize incorrect format such as 3+ only if not penalized in 4 (b).
[1]
(v)
[Ar]
;
[1]
(4s)
(3d)
Penalise missing [Ar] only once in (v) and (vi).
Do not accept full orbital diagram; penalise only once in (v) and (vi).
Accept full or half-arrows in (v) and (vi).
Ignore absence of labels 4s and 3d.
(vi)
[Ar]
(3d)
Accept empty 4s box in (vi).
No ECF from (iv).
;
[1]
– 10 –
(c)
(i)
M13/4/CHEMI/HP2/ENG/TZ1/XX/M
– +
positive electrode
negative electrode
electrolyte
clear diagram containing all elements (power supply, connecting wires,
electrodes, container and electrolyte);
Accept power supply if shown as conventional long/short lines (as in diagram
above) or clearly labelled DC power supply.
labelled positive electrode/anode and negative electrode/cathode;
Accept positive and negative by correct symbols near power supply.
labelled electrolyte/FeBr2 (l)/FeBr2(aq);
State must be included for FeBr2.
(ii)
Electrolyte: positive ions/cations move to negative electrode/cathode and
negative ions/anions to positive electrode/anode;
Conductors: electrons flow from negative pole of battery to positive pole of
battery / OWTTE;
Look at diagram in (i) for possible clarification of electron flow.
[3]
[2]
Award [1 max] for “electrons in wire/external circuit and ions in solution”.
(iii) Negative electrode/cathode:
H2;
E Ö (H2) is less negative than E Ö (Fe) / Fe is more reactive than H2 / H2 is lower
in reactivity series / H+ more easily reduced than Fe2+ / OWTTE;
Positive electrode/anode:
O2;
E Ö (O2) is less positive than E Ö (Br2) / in a dilute Br– solution OH–/H2O is
preferably discharged / OWTTE;
Award [3 max] if electrodes reversed or omitted.
(iv) Br2;
Accept Fe.
(v)
2Br –  Br2 + 2e – shifts to the right;
Accept similar reason for Fe.
[4]
[1]
[1]
– 11 –
8.
(a)
(i)
M13/4/CHEMI/HP2/ENG/TZ1/XX/M
(q = mcΔT =) 0.0500 × 4.18 × 21.3 = 4.45 (kJ);
Do not accept m = 0.05023 kg.
(n methanol =)
0.230
= 7.18 × 10–3 (mol) ;
32.05
4.45
;
7.18 × 10 –3
ΔH = –6.20 ×102 kJ mol–1;
Accept integer values of molar mass.
Final answer must have negative sign and correct units.
Award [4] for correct final answer with correct units.
ΔH =
(ii)
(b)
(i)
less heat is liberated than theoretically/–726 kJ mol–1;
probably due to heat loss/incomplete combustion;
determine heat capacity of calorimeter and take heat absorbed by calorimeter
into account / any suitable insulation method / measure temperature with time
and extrapolation of graph to compensate heat loss / OWTTE;
If the value calculated in (a) (i) is more exothermic than theoretically, allow
ECF for M1 and for improvement if consistent.
CH 3 OH + 32 O 2 → CO 2 + 2H 2 O
CO + 12 O 2 → CO 2
[4]
[3]
ëH Ö c = −726 (kJ mol –1 )
ëH Ö c = −283 (kJ mol –1 )
H 2 + 12 O 2 → H 2 O
ëH Ö c = −286 (kJ mol –1 )
Award [1 max] for three correct values.
Mark can be implicit in calculations.
(ëH Ö R =) 2( −286) + ( −283) − (−726) ;
–129 (kJ mol–1);
Award [3] for correct final answer.
Award [2 max] for +129 (kJ mol–1).
[3]
(ii)
(ëS Ö = 240 − 198 − 2 ×131 =) − 220(J K −1 mol−1 ) ;
[1]
(iii)
(−129 − 298(−0.220) =) − 63.4 kJ mol−1 ;
Award [1] for correct numerical answer and [1] for correct unit if the
conversion has been made from J to kJ for ëS Ö .
[2]
(iv) not spontaneous at high temperature;
T ëS Ö < ΔH Ö and ëG Ö positive;
[2]
– 12 –
(c)
(i)
(ii)
(iii)
M13/4/CHEMI/HP2/ENG/TZ1/XX/M
rate of forward reaction equals rate of backward reaction;
concentrations of reactants and products do not change / constant macroscopic
properties;
[CH 3OH]
;
[CO][H 2 ]2
Do not award mark if incorrect brackets are used or brackets omitted.
Kc =
(i)
(ii)
[1]
n(CO) = 0.508 (mol);
n(H 2 ) = 2 × 0.508 (mol);


0.492
= 0.938 ;
Kc  =
2 
 0.508 × (2 × 0.508) 
Accept answer in range between 0.930 and 0.940.
Award [3] for correct final answer.
Award [2] for Kc = 1.066 if (c)(ii) is correct.
(d)
[2]
[3]
shifts to left/reactants;
to endothermic side / (forward) reaction is exothermic;
[2]
shifts to the right/products;
to the side with fewer gas molecules/moles of gas;
[2]
– 13 –
9.
(a)
(i)
M13/4/CHEMI/HP2/ENG/TZ1/XX/M
same functional group / same general formula;
difference between successive members is CH2;
similar chemical properties;
Do not accept “same” chemical properties.
gradually changing physical properties;
(ii)
[3 max]
adding bromine (water);
but-2-ene: brown/orange to colourless / decolourizes bromine water and
butane: does not change colour;
[2]
OR
adding acidified potassium permanganate solution/KMnO4(aq);
but-2-ene: purple to colourless/brown and
butane: does not change colour;
OR
adding Baeyer’s reagent;
but-2-ene: purple/pink to brown and
butane: does not change colour;
Do not accept “clear” or “transparent” for “colourless”.
(iii)
H
H
H
H
H
C
C
C
C
H
H
H
+ HBr
H
H
H
H
H
C
C
C
C
H
Br
H
H
Accept condensed structural formula.
Penalise missing H atoms or incorrect bonds (such as C–HO, C–H2C) once
only in the whole paper.
(iv) compounds with the same structural formula but different arrangement of
atoms (in space);
(v)
H
[1]
[1]
(but-2-ene exists as) cis-but-2-ene and trans-but-2-ene /
;
cis
restricted rotation of C=C/double bond;
trans
[2]
– 14 –
(b)
(c)
M13/4/CHEMI/HP2/ENG/TZ1/XX/M
(i)
C4 H 9 Br + OH – → C4 H 9OH + Br – ;
Accept NaOH in the equation.
[1]
(ii)
decreases;
[1]
(i)
C4H9Br:
[C4H9Br] doubles and time halves/rate doubles/rate proportional to [C4H9Br];
Do not accept rate increases when [C4H9Br] increases.
NaOH:
[NaOH] doubles and time/rate does not change/rate independent of [NaOH];
(ii)
C4H9Br: first order and NaOH: zero order;
[3]
rate = k [C4 H 9 Br] ;
Accept ECF.
[1]
(iii) s–1;
Accept ECF.
(iv) rate depends on [C4H9Br] only / rate does not depend on [OH–] / SN1 reaction /
first order reaction / if it was primary, reaction would be SN2;
tertiary;
Accept ECF.
(v)
(CH3)3CBr;
Allow both condensed and full structural formula.
Accept ECF.
[1]
[2]
[1]
– 15 –
(d)
M13/4/CHEMI/HP2/ENG/TZ1/XX/M
(i)
curly arrow showing Br– leaving;
representation of tertiary carbocation;
curly arrow going from lone pair/negative charge on O in –OH to C+;
Do not allow arrow originating on H in –OH.
formation of (CH3)3COH and Br–;
Accept Br– anywhere on product side in the reaction scheme.
[4]
If primary halogenoalkane has been answered in (c)(iv) apply ECF for the
mechanism.
curly arrow going from lone pair/negative charge on O in –OH to C;
Do not allow curly arrow originating on H in –OH.
curly arrow showing Br– leaving;
Accept curly arrow either going from bond between C and Br to Br in
bromobutane or in the transition state.
representation of transition state showing negative charge, square brackets and
partial bond;
Do not penalize if HO and Br are not at 180 ° to each other.
Do not award M3 if OH—C bond is represented.
formation of organic product C4H9OH and Br–;
Accept Br– anywhere on product side in the reaction scheme.
(ii)
greater stability of tertiary carbocation;
steric hindrance for SN2 mechanism;
positive inductive effect (of alkyl groups);
Do not allow ECF.
(iii) the first step / Br– leaving / formation of carbocation;
Do not allow ECF.
[1 max]
[1]
M13/4/CHEMI/HP2/ENG/TZ2/XX
22136114
CHEMISTRY
HIGHER LEVEL
PAPER 2
Candidate session number
0
0
Thursday 16 May 2013 (afternoon)
Examination code
2
2 hours 15 minutes
2
1
3
–
6
1
1
4
INSTRUCTIONS TO CANDIDATES
•
•
•
•
•
•
•
•
Write your session number in the boxes above.
Do not open this examination paper until instructed to do so.
Section A: answer all questions.
Section B:answer two questions.
Write your answers in the boxes provided.
A calculator is required for this paper.
A clean copy of the Chemistry Data Booklet is required for this paper.
The maximum mark for this examination paper is [90 marks].
36 pages
© International Baccalaureate Organization 2013
0136
–2–
M13/4/CHEMI/HP2/ENG/TZ2/XX
SECTION A
Answer all questions. Write your answers in the boxes provided.
1.
Iron tablets are often prescribed to patients. The iron in the tablets is commonly present as iron(II) sulfate, FeSO4 .
(a)
[1]
State the function of iron in the human body.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Two students carried out an experiment to determine the percentage by mass of iron in a brand
of tablets marketed in Cyprus.
Experimental Procedure:
• The students took five iron tablets and found that the total mass was 1.65 g.
• The five tablets were ground and dissolved in 100 cm3 dilute sulfuric acid, H2SO4 (aq). The solution and washings were transferred to a 250 cm3 volumetric flask and made up to
the mark with deionized (distilled) water.
• 25.0 cm3 of this Fe2+ (aq) solution was transferred using a pipette into a conical flask. Some dilute sulfuric acid was added.
• A titration was then carried out using a 5.00 × 10–3 mol dm–3 standard solution of
potassium permanganate, KMnO4 (aq). The end-point of the titration was indicated by a
slight pink colour.
The following results were recorded.
Initial burette reading /
cm3 ± 0.05
Final burette reading /
cm3 ± 0.05
Rough titre
First accurate
titre
Second accurate
titre
1.05
1.20
0.00
20.05
18.00
16.80
(This question continues on the following page)
0236
–3–
M13/4/CHEMI/HP2/ENG/TZ2/XX
(Question 1 continued)
(b)
When the Fe2+(aq) solution was made up in the 250 cm3 volumetric flask, deionized
(distilled) water was added until the bottom of its meniscus corresponded to the graduation
mark on the flask. It was noticed that one of the two students measured the volume of the
solution from the top of the meniscus instead of from the bottom. State the name of this
type of error.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(c)
State what is meant by the term precision.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (d)
When the students recorded the burette readings, following the titration with KMnO4 (aq),
the top of the meniscus was used and not the bottom. Suggest why the students read the
top of the meniscus and not the bottom.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
0336
–4–
M13/4/CHEMI/HP2/ENG/TZ2/XX
(Question 1 continued)
(e)
This experiment involves the following redox reaction.
5Fe 2+ (aq) + MnO 4 − (aq) + 8H + (aq) → 5Fe3+ (aq) + Mn 2+ (aq) + 4H 2 O (l)
(i)
Define the term reduction in terms of electrons.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Deduce the oxidation number of manganese in the MnO4– (aq) ion.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
0436
–5–
M13/4/CHEMI/HP2/ENG/TZ2/XX
(Question 1 continued)
(f)
(i)
Determine the amount, in mol, of MnO4– (aq), used in each accurate titre.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Calculate the amount, in mol, of Fe2+ (aq) ions in 250 cm3 of the solution.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) Determine the total mass of iron, in g, in the 250 cm3 solution.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [1]
(iv) Determine the percentage by mass of iron in the tablets.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
0536
–6–
M13/4/CHEMI/HP2/ENG/TZ2/XX
(Question 1 continued)
(g)
During the rough titration, the students found that a brown precipitate, X, formed.
(i)
When the students discussed the nature of the precipitate with their teacher,
they were told that X is the same compound as that used as a catalyst in the
decomposition of hydrogen peroxide, H2O2 (aq), to prepare oxygen, O2 (g). Suggest the chemical formula and name of X.
[2]
Chemical formula:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Name:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
State the balanced chemical equation for the decomposition of hydrogen peroxide.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) Suggest how the formation of the brown precipitate might be prevented.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
0636
–7–
M13/4/CHEMI/HP2/ENG/TZ2/XX
(Question 1 continued)
(h)
(i)
Following the experiment, the students proposed the following hypothesis:
“Since sulfuric acid is a strong acid, two other strong acids such as nitric acid,
HNO3 (aq) or hydrochloric acid, HCl (aq), could also be used in this experiment”.
Suggest one problem with this hypothesis.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
The students also explored the role of sulfuric acid in everyday processes and found
that sulfuric acid present in acid rain can damage buildings made of limestone. Predict the balanced chemical equation for the reaction between limestone and
sulfuric acid, including state symbols.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Turn over
0736
–8–
2.
Consider the following graph of ln k against
M13/4/CHEMI/HP2/ENG/TZ2/XX
1
.
T
–5.50
–6.00
ln k
–6.50
–7.00
–7.50
3.15
3.20
3.25
3.30
3.35
3.40
1
/ 10−3 K −1
T
(a)
A catalyst provides an alternative pathway for a reaction, lowering the activation
energy, Ea . Define the term activation energy, Ea .
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
State how the rate constant, k , varies with temperature, T.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
0836
–9–
M13/4/CHEMI/HP2/ENG/TZ2/XX
(Question 2 continued)
(c)
Determine the activation energy, Ea , correct to three significant figures and state its units.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
0936
– 10 –
3.
M13/4/CHEMI/HP2/ENG/TZ2/XX
Carboplatin used in the treatment of lung cancer has the following three-dimensional structure.
O
H
H
N
H
H
N
H
(a)
O
C
Pt
H
H
C
H
C
C
O
H
C
C
O
H
H
H
Identify the name of the functional group circled in the structure of carboplatin.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
State the type of bonding between platinum and nitrogen in carboplatin.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
1036
– 11 –
M13/4/CHEMI/HP2/ENG/TZ2/XX
(Question 3 continued)
(c)
Elemental platinum has electrons occupying s, p, d and f atomic orbitals.
(i)
Draw the shape of an s orbital and a px orbital. Label the x, y and z axes on
each diagram.
s orbital
(ii)
[2]
px orbital
[1]
State the maximum number of orbitals in the n = 4 energy level.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (d)
A number of ruthenium-based anti-cancer drugs have also been developed. State the full
electron configuration of the ruthenium(II) ion, Ru2+.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
1136
– 12 –
M13/4/CHEMI/HP2/ENG/TZ2/XX
(Question 3 continued)
(e)
Iron is in the same group in the periodic table as ruthenium.
Construct the orbital diagram (using the arrow-in-box notation) for iron, showing the
electrons in the n = 3 and n = 4 energy levels only and label each sub-level on the
diagram.
......
......
......
1236
......
[1]
– 13 –
4.
(a)
M13/4/CHEMI/HP2/ENG/TZ2/XX
Hydrogen gas reacts with iodine gas to form hydrogen iodide gas. A 2.00 dm3 flask was
filled with 1.50 × 10–2 mol of hydrogen and 1.50 × 10–2 mol of iodine at a temperature, T. The equilibrium constant, Kc , has a value of 53.0 at this temperature.
(i)
Deduce the equilibrium constant expression, Kc , for the formation of HI (g).
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Determine the equilibrium concentrations, in mol dm–3, of hydrogen, iodine and
hydrogen iodide.
[4]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
Identify the intermolecular forces present in hydrogen iodide in the liquid state, HI (l).
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
1336
– 14 –
M13/4/CHEMI/HP2/ENG/TZ2/XX
(Question 4 continued)
(c)
Consider the compounds (CH3)2NH and CH4 .
(i)
State and explain which compound can form hydrogen bonds with water.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Draw a diagram showing the resulting hydrogen bonds between water and the
compound chosen in (i).
(iii) Apply IUPAC rules to state the name of (CH3)2NH.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1436
[1]
[1]
– 15 –
M13/4/CHEMI/HP2/ENG/TZ2/XX
SECTION B
Answer two questions. Write your answers in the boxes provided.
5.
Phosphoryl chloride, POCl3 , is a dehydrating agent.
(a)
POCl3 (g) decomposes according to the following equation.
2POCl3 (g) → 2PCl3 (g) + O 2 (g)
(i)
[1]
Predict and explain the sign of the entropy change, ∆S, for this reaction.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Calculate the standard entropy change for the reaction, ∆S Ö , in J K–1 mol–1, using
the data below.
Substance
S Ö / J K −1 mol −1
POCl3 (g)
325.0
PCl3 (g)
311.7
O2 (g)
205.0
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) Define the term standard enthalpy change of formation, ∆H f Ö.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
1536
– 16 –
M13/4/CHEMI/HP2/ENG/TZ2/XX
(Question 5 continued)
(iv) Calculate the standard enthalpy change for the reaction, ∆H Ö, in kJ mol–1, using the
data below.
Substance
∆H f Ö / kJ mol −1
POCl3 (g)
–542.2
PCl3 (g)
–288.1
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (v)
Determine the standard free energy change for the reaction, ∆G Ö, in kJ mol–1, at 298 K.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (vi) Deduce the temperature, in K, at which the reaction becomes spontaneous.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
1636
– 17 –
M13/4/CHEMI/HP2/ENG/TZ2/XX
(Question 5 continued)
(b)
(i)
Deduce the Lewis (electron dot) structure of POCl3 (with P as the central element)
and PCl3 and predict the shape of each molecule, using the valence shell electron
pair repulsion theory (VSEPR).
[4]
POCl3
PCl3
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lewis
(electron dot)
structure
Shape
(ii)
State and explain the Cl–P–Cl bond angle in PCl3.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [1]
(iii) State the balanced chemical equation for the reaction of PCl3(l) with water.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
1736
– 18 –
M13/4/CHEMI/HP2/ENG/TZ2/XX
(Question 5 continued)
(c)
POCl3 can be prepared by the reaction of phosphorus pentachloride, PCl5 , with
tetraphosphorus decaoxide, P4O10 .
(i)
Deduce the Lewis (electron dot) structure of PCl5 .
[1]
(ii)
Predict the shape of this molecule, using the valence shell electron pair repulsion
theory (VSEPR).
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) Identify all the different bond angles in PCl5 .
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
1836
– 19 –
M13/4/CHEMI/HP2/ENG/TZ2/XX
(Question 5 continued)
(iv) PCl3Br2 has the same molecular shape as PCl5 . Draw the three isomers of PCl3Br2
and deduce whether each isomer is polar or non-polar.
[3]
Isomer 1
Isomer 2
Isomer 3
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Structure
Molecular
polarity
(d)
PCl3 and Cl– can act as ligands in transition metal complexes such as Ni(PCl3)4 and
[Cr(H2O)3Cl3].
(i)
Define the term ligand.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
[3]
Explain why the complex [Cr(H2O)3Cl3] is coloured.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
1936
– 20 –
6.
M13/4/CHEMI/HP2/ENG/TZ2/XX
Acid–base chemistry can play a major role in chemical and biological processes.
(a)
Ammonia, NH3 , can be used to clean ovens. The concentration of hydroxide ions,
OH– (aq), in a solution of ammonia is 3.98 × 10–3 mol dm–3. Calculate its pH, correct to
one decimal place, at 298 K.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
White vinegar, which contains ethanoic acid, CH3COOH, can be used as a cleaning agent
to dissolve mineral deposits from coffee machines.
(i)
Define an acid according to the Brønsted–Lowry theory and the Lewis theory.
[2]
Brønsted–Lowry theory:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lewis theory:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Ethanoic acid is an example of a weak acid. Distinguish between a strong acid and
a weak acid in terms of the extent of dissociation.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
2036
– 21 –
M13/4/CHEMI/HP2/ENG/TZ2/XX
(Question 6 continued)
(c)
Buffer solutions play a pivotal role in solution chemistry.
(i)
State whether the following mixtures, in the appropriate molar ratios, can be
classified as buffer solutions. Show your answer by stating yes or no in the
table below.
Mixture
[1]
Buffer
HCOOH and HCOO–K+
HCl and excess NH3
(ii)
A buffer solution contains lactic acid, CH3CH(OH)COOH (aq), with a
concentration of 1.55 × 10–1 mol dm–3 and sodium lactate, NaCH3CH(OH)COO (aq),
with a concentration of 1.05 × 10–1 mol dm–3. Determine the pH of this buffer solution,
correct to two decimal places.
(Ka for lactic acid = 1.40 × 10–4 at 298 K.)
[4]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
2136
– 22 –
M13/4/CHEMI/HP2/ENG/TZ2/XX
(Question 6 continued)
(d)
Acid–base indicators are often organic dyes.
(i)
Describe qualitatively the action of an acid–base indicator.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Using Table 16 of the Data Booklet, identify the most appropriate indicator for the
titration of ethanoic acid with sodium hydroxide. Explain your choice.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) 150 cm3 of 5.00 × 10–1 mol dm–3 HCl (aq) is mixed with 300 cm3 of 2.03 × 10–1 mol dm–3
NaOH (aq). Determine the pH of the solution, correct to two decimal places.
[4]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
2236
– 23 –
M13/4/CHEMI/HP2/ENG/TZ2/XX
(Question 6 continued)
(e)
(i)
State and explain whether the following solutions will be acidic, basic or neutral.
[4]
FeCl3 :
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CH3CH2NH3NO3 :
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
The Ka value for HF is 6.80 × 10–4 at 298 K. Using this information and any
additional information from Tables 2 and 15 of the Data Booklet, deduce whether
a solution of NH4F would be acidic, basic or neutral.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
2336
– 24 –
7.
(a)
M13/4/CHEMI/HP2/ENG/TZ2/XX
Define oxidation in terms of oxidation number.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
(i)
Deduce the balanced chemical equation for the redox reaction of copper, Cu (s),
with nitrate ions, NO3– (aq), in acid, to produce copper(II) ions, Cu2+ (aq), and
nitrogen(IV) oxide, NO2 (g).
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Deduce the oxidizing and reducing agents in this reaction.
[1]
Oxidizing agent:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reducing agent:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
2436
– 25 –
M13/4/CHEMI/HP2/ENG/TZ2/XX
(Question 7 continued)
(c)
A voltaic cell was set up, using the standard hydrogen electrode as a reference electrode
and a standard Cu2+ (aq)/Cu (s) electrode.
(i)
[3]
Describe the standard hydrogen electrode including a fully labelled diagram.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Define the term standard electrode potential, E Ö .
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) Deduce a balanced chemical equation, including state symbols, for the overall
reaction which will occur spontaneously when the two half-cells are connected.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
2536
– 26 –
M13/4/CHEMI/HP2/ENG/TZ2/XX
(Question 7 continued)
(d)
Another voltaic cell was set up, using a Sn2+ (aq)/Sn (s) half-cell and a Cu2+ (aq)/Cu (s)
half-cell under standard conditions.
(i)
(ii)
Draw a fully labelled diagram of the voltaic cell, showing the positive electrode
(cathode), the negative electrode (anode) and the direction of electron movement
through the external circuit.
[3]
Using Table 14 of the Data Booklet, calculate the cell potential, E Ö cell , in V,
when the two half-cells are connected.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
2636
– 27 –
M13/4/CHEMI/HP2/ENG/TZ2/XX
(Question 7 continued)
(e)
Water in a beaker at a pressure of 1.01 × 105 Pa and a temperature of 298 K will not
spontaneously decompose. However, decomposition of water can be induced by means
of electrolysis.
(i)
Deduce the sign of the standard free energy change, ∆G Ö , for any non-spontaneous
reaction.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
State why dilute sulfuric acid needs to be added in order for the current to flow in
the electrolytic cell.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) State why copper electrodes cannot be used in the electrolysis of water. Suggest
instead suitable metallic electrodes for this electrolysis process.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
2736
– 28 –
M13/4/CHEMI/HP2/ENG/TZ2/XX
(Question 7 continued)
(iv) Deduce the half-equations for the reactions occurring at the positive electrode
(anode) and the negative electrode (cathode).
[2]
Positive electrode (anode):
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Negative electrode (cathode):
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (v)
Deduce the overall cell reaction, including state symbols.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
2836
– 29 –
M13/4/CHEMI/HP2/ENG/TZ2/XX
(Question 7 continued)
(vi) Draw a fully labelled diagram of the electrolytic cell, showing the positive
electrode (anode) and the negative electrode (cathode).
[2]
(vii) Comment on what is observed at both electrodes.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (f)
Two electrolytic cells are connected in series (the same current passes through
each cell). One cell for the electrolysis of water produces 100 cm3 of oxygen, measured
at 273 K and 1.01 × 105 Pa . The second cell contains molten lead(II) bromide, PbBr2 . Determine the mass, in g, of lead produced.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
2936
– 30 –
8.
M13/4/CHEMI/HP2/ENG/TZ2/XX
Geometrical isomerism and optical isomerism are two sub-groups of stereoisomerism in
organic chemistry.
(a)
Describe what is meant by the term stereoisomers.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
Geometrical isomers have different physical properties and many drugs, such as doxepin
(which has antidepressant properties), have geometrical isomers.
H
H
C
C
C
H
C
C
C
C
C
C
H
C
C
N
H
H
C
C
C
H
H
C
H
H
H
H
1
H
H
C
C
O
C
H
H
H
C
2
H
H
H
H
Example of a geometrical isomer of doxepin
For each of the carbon atoms labelled 1 and 2 in doxepin, deduce the type of
hybridization involved (sp, sp2 or sp3).
1:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [1]
(This question continues on the following page)
3036
– 31 –
M13/4/CHEMI/HP2/ENG/TZ2/XX
(Question 8 continued)
(c)
Clomifene, a fertility drug, whose three-dimensional structure is represented below,
also has geometrical isomers. H
H
Cl
C
H
C
H
H
C
H
C
H
C
H
C
H
H
C
C
H
C
N
H
H
O
C
H
H
C
H
H
H
C
C
H
H
H
C
C
H
C
C
H
C
C
C
C
C
C
C
H
C
H
C
H
H
H
Identify the name of one functional group present in clomifene.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
3136
– 32 –
M13/4/CHEMI/HP2/ENG/TZ2/XX
(Question 8 continued)
(d)
Compound P has the following three-dimensional structure. P also has geometrical
isomers.
H
H
H
H
H
C
C
C
C
H
H
H
P
(i)
Draw any two other isomers of P.
[2]
(ii)
Apply IUPAC rules to state the names of all the straight-chain isomers of
compounds of molecular formula C4H8 (including P).
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
3236
– 33 –
M13/4/CHEMI/HP2/ENG/TZ2/XX
(Question 8 continued)
(iii) State the structural formula of the organic products, Q, R, S and T, formed in the
following reactions.
CH3CH=CHCHP3
+
HBr (g)

→
[4]
Q
Q:
P3
CH3CH=CHCH
R:
(1) concentrated
H2SO4 (aq)

→
(2) H2O(l)
P3 +
CH3CH=CHCH
Br2 (aq)
R

→
S
S:
Q
+
OH − (aq)

→
T
T:
(This question continues on the following page)
Turn over
3336
– 34 –
M13/4/CHEMI/HP2/ENG/TZ2/XX
(Question 8 continued)
(iv) Suggest one suitable mechanism for the reaction of Q with aqueous sodium
hydroxide to form T, using curly arrows to represent the movement of
electron pairs.
[4]
State the structural formula of the organic product formed, U, when R is heated
under reflux with acidified potassium dichromate(VI).
[1]
(v)
(vi) Apply IUPAC rules to state the name of this product, U.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
3436
– 35 –
M13/4/CHEMI/HP2/ENG/TZ2/XX
(Question 8 continued)
(e)
Menthol can be used in cough medicines. The compound contains C, H and O only.
(i)
When a 6.234 × 10−2 g of the compound was combusted, 1.755 × 10−1 g of carbon
dioxide and 7.187 × 10−2 g of water were produced. Determine the molecular
formula of the compound showing your working, given that its molar mass is
M = 156.30 g mol−1 .
[4]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Menthol occurs naturally and has several isomers. State the structural feature of
menthol which is responsible for it having enantiomers.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
3536
– 36 –
M13/4/CHEMI/HP2/ENG/TZ2/XX
(Question 8 continued)
(iii) State the instrument used to distinguish between each of the two enantiomers,
and how they could be distinguished using this instrument.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv) Compare the physical and chemical properties of enantiomers.
Physical properties:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chemical properties:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3636
[2]
M13/4/CHEMI/HP2/ENG/TZ2/XX/M
MARKSCHEME
May 2013
CHEMISTRY
Higher Level
Paper 2
24 pages
–2–
M13/4/CHEMI/HP2/ENG/TZ2/XX/M
This markscheme is confidential and for the exclusive use of
examiners in this examination session.
It is the property of the International Baccalaureate and must not
be reproduced or distributed to any other person without the
authorization of the IB Assessment Centre.
–3–
M13/4/CHEMI/HP2/ENG/TZ2/XX/M
Subject Details: Chemistry HL Paper 2 Markscheme
Mark Allocation
Candidates are required to answer ALL questions in Section A [40 marks] and TWO questions in
Section B [2 x 25 marks]. Maximum total = [90 marks].
1.
A markscheme often has more marking points than the total allows. This is intentional.
2.
Each marking point has a separate line and the end is shown by means of a semicolon (;).
3.
An alternative answer or wording is indicated in the markscheme by a slash (/). Either wording can
be accepted.
4.
Words in brackets ( ) in the markscheme are not necessary to gain the mark.
5.
Words that are underlined are essential for the mark.
6.
The order of marking points does not have to be as in the markscheme, unless stated otherwise.
7.
If the candidate’s answer has the same “meaning” or can be clearly interpreted as being of
equivalent significance, detail and validity as that in the markscheme then award the mark.
Where this point is considered to be particularly relevant in a question it is emphasized by
OWTTE (or words to that effect).
8.
Remember that many candidates are writing in a second language. Effective communication is more
important than grammatical accuracy.
9.
Occasionally, a part of a question may require an answer that is required for subsequent
marking points. If an error is made in the first marking point then it should be penalized. However,
if the incorrect answer is used correctly in subsequent marking points then follow through marks
should be awarded. When marking, indicate this by adding ECF (error carried forward) on the
script.
10.
Do not penalize candidates for errors in units or significant figures, unless it is specifically referred
to in the markscheme.
11.
If a question specifically asks for the name of a substance, do not award a mark for a correct
formula unless directed otherwise in the markscheme. Similarly if the formula is specifically asked
for, unless directed otherwise in the markscheme, do not award a mark for a correct name.
12.
If a question asks for an equation for a reaction, a balanced symbol equation is usually expected, do
not award a mark for a word equation or an unbalanced equation unless directed otherwise in the
markscheme.
13.
Ignore missing or incorrect state symbols in an equation unless directed otherwise in the
markscheme.
–4–
M13/4/CHEMI/HP2/ENG/TZ2/XX/M
SECTION A
1.
(a)
for hemoglobin / myoglobin / transport of oxygen / enzyme / catalase / catalyst;
Allow heme instead of hemoglobin.
[1]
(b)
systematic (error);
Do not accept parallax.
[1]
(c)
closeness of agreement of a set of measurements to each other / OWTTE;
Allow reproducibility/consistency of measurement / measurements with small
random errors/total amount of random errors/standard deviation / a more precise
value contains more significant figures / OWTTE.
[1]
(d)
potassium permanganate has a very dark/deep (purple) colour so cannot read
bottom of meniscus / OWTTE;
[1]
(i)
gain (of electrons);
[1]
(ii)
VII / +7;
Do not accept 7 or 7+.
[1]
(i)
volume = 16.80 (cm3 ) / 18.00 − 1.20 (cm3 ) ;
(e)
(f)
 16.80 × 5.00 × 10−3 
−5
amount  =
 = 8.40 ×10 (mol) ;
1000


Award [2] for correct final answer.
(ii)
(8.40 × 10−5 × 5 × 10) = 4.20 × 10−3 (mol per 250 cm3 ) ;
(iii) (55.85 × 4.20 × 10−3 ) = 0.235 (g);
Do not penalize if 56 g mol–1 is used for atomic mass of iron.
(iv)
(g)
(i)
(ii)
 0.235 ×100 
= 14.2 % ;

 1.65

No ECF if answer >100 %.
Chemical formula: MnO 2 ;
Name: manganese(IV) oxide;
Allow manganese dioxide.
No ECF if formula is incorrect.
2H 2 O 2 (aq) → 2H 2 O (l) + O 2 (g) / H 2 O 2 (aq) → H 2 O (l) + 12 O 2 (g) ;
Ignore state symbols.
(iii) add more (sulphuric) acid/H2SO4 / ensure enough (sulphuric) acid/H2SO4 is
present / OWTTE;
Award [0] if reference made to HCl or HNO3.
[2]
[1]
[1]
[1]
[2]
[1]
[1]
–5–
(h)
(i)
(ii)
2.
(a)
M13/4/CHEMI/HP2/ENG/TZ2/XX/M
NO3– and Cl– anions may also react with KMnO4 / HNO3 is an oxidizing
agent / (HCl will not work as) Cl– reacts with MnO4– (to form Cl2) / HCl
oxidized / OWTTE;
For HCl, allow correctly balanced chemical equation:
2MnO4 − + 10Cl − + 16 H + → 2Mn 2+ + 5Cl2 + 8H 2O
Accept NO3– and Cl– may react with KMnO4/Fe2+.
CaCO3 (s) + H 2SO 4 (aq) → CaSO 4 (s) + H 2 O (l) + CO 2 (g)
correct chemical equation;
correct state symbols;
Allow CaSO4(aq) instead of CaSO4(s).
M2 can only be scored if M1 is correct.
Award [1max] if H2CO3(aq) is given instead of H2O(l) + CO2(g).
minimum energy needed (by reactants/colliding particles) to react/start/initiate
a reaction / for a successful collision;
Allow energy difference between reactants and transition state.
(b)
k increases with T;
Do not accept k proportional to T or statement of Arrhenius equation from Data
booklet.
(c)
slope/gradient/m =
[1]
[2]
[1]
[1]
− Ea
/ −6.20 ×103 ;
R
Allow range of m from −5.96 × 10 3 to −6.44 × 10 3.
− Ea
even if gradient is out of range.
Award M1 for m =
R
Ea = (6.20 × 103 × 8.31) = 51.5 kJ mol−1 / 5.15 × 104 J mol−1
Ea value correct;
units correct;
Award [3] for correct final answer.
Allow range of Ea from 49.5 to 53.5 kJ mol–1/ 4.95 × 10 4 to 5.35 × 10 4 J mol–1.
Answer must be given correct to three significant figures.
M3 can be scored independently.
[3]
–6–
3.
M13/4/CHEMI/HP2/ENG/TZ2/XX/M
(a)
ester;
Do not accept just carbonyl.
Allow carboxylato (ligand)/carboxylate (ligand) but not carboxyl/carboxy.
[1]
(b)
dative (covalent) / coordinate;
Do not allow just covalent or co-dative.
[1]
(c)
(i)
y
x
z
symmetrical s orbital representation;
Do not penalize if axes are not labelled for s orbital.
x, y, z can be located in any direction.
y
x
z
dumbbell-shaped px orbital representation with electron density located
[2]
along x-axis;
x-axis must be labelled for px orbital.
Do not accept if py and pz are also drawn as question asks for orbital not sub-level.
(ii)
(d)
16;
[1]
1s 2 2s 2 2p6 3s 2 3p6 4s 2 3d10 4p 6 4d 6 ;
Order of 4s and 3d levels can be interchanged.
Do not accept other notation such as subscripts.
(e)
[1]
;
3s
3p
4s
3d
Allow full arrows instead of half-arrows in orbital diagram.
Sub-levels must be labelled for mark.
[1]
–7–
4.
(a)
(i)
(ii)
M13/4/CHEMI/HP2/ENG/TZ2/XX/M
[HI]2
[HI]
/
1
1 ;
[H 2 ][I 2 ] [H 2 ] 2 [I 2 ] 2
Do not award mark if brackets are omitted or incorrect.
( K c =)
+I2
H2
(7.50 ×10−3 − x) (7.50 ×10−3 − x)
(1.50 ×10−2 − x) (1.50 × 10−2 − x)
[H 2 ]initial − x
[I 2 ]initial − x
[1]
→ 2HI
2x /
2x /
2 x;
Accept [H 2 ]initial = [I 2 ]initial = 7.50 × 10 −3 (mol dm −3 ) for M1.
(2 x) 2
53 =
/
(7.50 ×10−3 − x) 2
Accept 53 =
53 =
(2 x)
;
(7.50 × 10−3 − x)
(2x )2
/
(1.50 × 10 −2 − x )2
53 =
(2x )
.
−2
(1.50 × 10 − x )
[H 2 ] = 1.62 ×10−3 (mol dm −3 ) and [I 2 ] = 1.62 × 10−3 (mol dm −3 ) ;
[HI] = 1.18 ×10−2 ;
Award [4] for correct final answer for values given in M3 and M4.
Award [2 max] for [H 2 ] = [I 2 ] = 7.50 × 10 −3 (mol dm −3 ) and
[HI] = 5.46 × 10 −2 mol dm −3 .
OR
if K c =
[HI]
1
1
[H 2 ] 2 [I 2 ] 2
1
H2
2
(7.50 ×10−3 − x)
(1.50 ×10−2 − x)
[H 2 ]initial − x
is given in (i).
1
+ I2
2
(7.50 ×10−3 − x)
(1.50 × 10−2 − x)
[I 2 ]initial − x
→ HI
2x /
2x /
2 x;
Accept [H 2 ]initial = [I 2 ]initial = 7.50 × 10 −3 (mol dm −3 ) for M1.
(2 x)
;
(7.50 × 10−3 − x)
(2x )
Accept 53 =
.
(1.50 × 10 −2 − x )
53 =
[H 2 ] = 2.73 ×10−4 mol dm −3 and [I 2 ] = 2.73 ×10−4 mol dm −3 ;
[HI] = 1.45 ×10−2 mol dm −3 ;
Award [4] for correct final answer for values given in M3 and M4.
Award [2 max] for [H 2 ] = [I 2 ] = 7.50 × 10 −3 (mol dm −3 ) and
[HI] = 5.46 × 10 −2 mol dm −3 .
[4]
–8–
M13/4/CHEMI/HP2/ENG/TZ2/XX/M
(b)
van der Waals’/London/dispersion and dipole-dipole;
Allow abbreviations for van der Waals’ as vdW or for London/dispersion as FDL.
(c)
(i)
(ii)
[1]
(CH 3 ) 2 NH ;
(intermolecular) attraction between hydrogen (atom) in O–H/N–H (polar)
bond and (lone pair on) electronegative N/O / hydrogen between two very
electronegative elements (nitrogen and oxygen) / OWTTE;
Accept hydrogen bonded to nitrogen which is electronegative/has
lone pair.
Do not allow ECF if M1 is incorrect.
[2]
representative drawing showing hydrogen bond between (CH3)2NH and
H2O;
CH3
CH3
[1]
H
N
H
O
H
O
H
N
H
CH3
H
CH3
Do not penalize if lone pair as part of hydrogen bond is not shown.
Allow any representation of hydrogen bond (for example, dashed lines, dots
etc.) which differs from full stick representation of the other covalent bonds
in amine and water molecules.
Allow full line if labelled as hydrogen bond.
Lone pairs on oxygen not necessary.
Award mark if two hydrogen bonds drawn between the molecules from the
lone pair and the H on the N.
(iii) N-methylmethanamine / methylmethanamine / dimethylamine;
Do not accept N–N dimethylamine.
[1]
–9–
M13/4/CHEMI/HP2/ENG/TZ2/XX/M
SECTION B
5.
(a)
(i)
(ii)
2 mol (g) going to 3 mol (g)/increase in number of particles, therefore
entropy increases/ΔS positive / OWTTE;
Accept if numbers of moles of gas are given below the equation.
[1]
( ΔS
[1]
Ö
= [(2)(311.7) + (205.0)] − (2)(325.0) = ) (+)178.4 (J K −1 mol−1 ) ;
(iii) heat/enthalpy change/required/absorbed when 1 mol of a compound is
formed from its elements in their standard states/at 100 kPa/105 Pa/1 bar;
Allow 1.01 × 10 5 Pa / 101kPa / 1atm .
Allow under standard conditions or standard temperature and pressure.
Temperatures not required in definition, allow if quoted (for example,
298 K/ 25 °C – most common) but pressure value must be correct if stated.
(iv)
( ΔH
(v)

 178.4  
Ö
Ö
Ö
−1
 ΔG = ΔH − T ΔS = (508.2) − (298)  1000  =  (+ ) 455.0 (kJ mol ) ;

 

Ö
= [(2)(−288.1)] − [(2)(−542.2)]) = ) (+) 508.2 (kJ mol −1 ) ;


 ΔH Ö
508.2 
(vi) T > 
=
=  2849 (K) /2576 (°C) ;
Ö
178.4
Δ
S





 

1000

 

Allow temperatures in the range 2848–2855 K.
Accept T = 2849(K) .
No ECF for temperatures T in the range 0–100 K.
[1]
[1]
[1]
[1]
(b)
(i)
– 10 –
M13/4/CHEMI/HP2/ENG/TZ2/XX/M
POCl3
PCl3
P
Cl
Cl
;
Cl
Lewis
(electron dot)
Structure
Accept legitimate alternatives
for POCl3 as shown below*.
Allow any combination of dots/crosses or lines to represent
electron pairs.
Penalise missing lone pair on P in PCl3 but penalize missing
lone pairs once only on terminal O or Cl atoms.
trigonal/triangular
pyramidal;
tetrahedral;
Do not allow tetrahedral.
Do not allow just pyramidal.
Shape
Do not allow ECF from Lewis structures with incorrect
number of negative charge centres.
Only allow shapes based on legitimate structures below.
[4]
*Legitimate alternatives for POCl3:
(ii)
(iii)
allow any bond angle in the range 100 to less than 109 (experimental
value is100 );
due to four negative charge centres/four electron pairs/four electron domains
(one of which is a lone pair)/tetrahedral arrangement of electron
pairs/domains;
extra repulsion due to lone pair electrons / lone pairs occupy more space
(than bonding pairs) so Cl–P–Cl bond angle decreases from 109.5 /
OWTTE;
PCl3 (l) + 3H 2 O (l) → H 3PO3 (aq) + 3HCl (aq) ;
Ignore state symbols.
Do not accept P(OH)3 for H3PO3.
[3]
[1]
– 11 –
(c)
(i)
M13/4/CHEMI/HP2/ENG/TZ2/XX/M
Cl
Cl
Cl
P
;
Cl
Cl
[1]
Allow any combination of dots/crosses or lines to represent electron pairs.
Do not penalise missing lone pairs on Cl if already penalised in (b)(i).
(ii)
trigonal/triangular bipyramidal;
Do not allow ECF from Lewis structures with incorrect number of
negative charge centres.
(iii) 120 and 90 /180 ;
Ignore other bond angles such as 240  and 360  .
Apply list principle if some correct and incorrect angles given.
(iv)
Structure
(d)
(i)
(ii)
[1]
Isomer 1
Isomer 2
Isomer 3
both Br’s in
axial positions,
all Cl’s in
equatorial
positions
both Br’s in
equatorial
positions, two Cl’s
in axial positions,
one Cl in
equatorial position
one Br in
equatorial
position, one Br in
axial position, one
Cl in axial position
and two Cl’s in
equatorial
positions
Molecular
non-polar
polar
polarity
Award [1] for correct structure and molecular polarity.
Award [1 max] for correct representations of all three isomers.
Lone pairs not required.
[1]
polar
species with lone/non-bonding pair (of electrons);
which bonds to metal ion (in complex) / which forms dative
(covalent)/coordinate bond to metal ion (in complex);
unpaired electrons in d orbitals / d sub-level partially occupied;
d orbitals split (into two sets of different energies);
frequencies of (visible) light absorbed by electrons moving from lower to
higher d levels;
colour due to remaining frequencies / complementary colour transmitted;
Allow wavelength as well as frequency.
Do not accept colour emitted.
[3]
[2]
[3max]
– 12 –
6.
(a)
[H 3O + ] =
M13/4/CHEMI/HP2/ENG/TZ2/XX/M
Kw
(1.00 × 10−14 )
=
= 2.51× 10−12 (mol dm −3 ) ;
[OH − ] (3.98 × 10−3 )
pH ( = − log[H 3O + ] = − log(2.51×10−12 ) ) = 11.6 ;
[2]
OR
pOH = ( − log (5.98 × 10−3 ) = ) 2.4 ;
pH = (14.00 − 2.40) = 11.6 ;
Award [2] for correct final answer.
Allow correct use of H+ instead of H3O+ throughout.
(b)
(i)
(ii)
(c)
Brønsted-Lowry theory:
proton/H+ donor;
Lewis theory:
electron pair acceptor;
[2]
Strong acid: acid/electrolyte (assumed to be almost) completely/100%
dissociated/ionized (in solution/water) / OWTTE and Weak acid:
acid/electrolyte partially dissociated/ionized (in solution/water) / OWTTE;
[1]
(i)
Mixture
Buffer
HCOOH and KHCOO
Yes
HCl and excess NH3
Yes;
[1]
Award [1] for both “yes”.
Award [0] for any “no”.
(ii)
Ka =
K [HX]
[H 3O + ][X − ]
/ [H 3O + ] = a − ;
[X ]
[HX]
1.40 ×10−4 × 1.55 × 10−1
;
1.05 × 10−1
[H3O + ] = 2.07 ×10−4 (mol dm −3 ) ;
[H 3O + ] =
pH ( = − log (2.07 ×10−4 ) ) = 3.68 ;
OR
pK a = 3.854 ;
[X − ]
[HX]
pH = pK a + log
/ pH = pK a − log
;
[HX]
[X − ]
pH = 3.854 − 0.169 ;
pH = 3.68 ;
Award [4] for correct final answer.
Allow correct use of H+ instead of H3O+ throughout.
Allow acid for HX, conjugate base/salt for X – throughout.
[4]
– 13 –
(d)
(i)
HIn (aq)  H + (aq) + In − (aq) /
Colour A
Colour B
M13/4/CHEMI/HP2/ENG/TZ2/XX/M
HIn (aq) + H 2 O (l)  In − (aq) + H 3O + (aq) ;
Colour A
Colour B
Allow statement such as solution of weak acid with different colours for
conjugate base/In–(aq) and undissociated acid/HIn(aq) / OWTTE.
Equilibrium sign required.
Ignore state symbols.
Allow corresponding argument for an indicator as a weak base.
for example, BOH (aq)  B + (aq) + OH − (aq) etc.
in acid/presence of H+ equilibrium lies to left (so colour A);
in alkali/base/presence of OH– equilibrium lies to right (so colour B);
colour changes/end point when [HIn (aq)] ≈ [In − (aq)] ;
(ii)
(iii)
phenolphthalein/phenol red;
indicator changes colour in range of pH at equivalence point which is
above 7 / OWTTE;
M2 can be scored independently even if indicator is incorrect.
Accept it is a titration of weak acid with a strong base for M2.
[3 max]
[2]
 (150 × 5.00 × 10−1 ) 
−2
n(HCl)  =
 = 7.50 × 10 (mol) and
(1000)


−1
 (300 × 2.03 × 10 ) 
−2
n(NaOH)  =
 = 6.09 ×10 (mol) ;
(1000)


n(HCl) remaining (= (7.50 − 6.09) ×10−2 ) = 1.41× 10−2 (mol) ;
[HCl] = (1.41×10−2 )(1000) / (450) = 3.13 ×10−2 (mol dm −3 ) ;
pH = 1.50 ;
Award [4] for correct final answer.
Award [3max] for pH = −log (1.41 × 10 −2 ) = 1.85 .
[4]
– 14 –
(e)
(i)
M13/4/CHEMI/HP2/ENG/TZ2/XX/M
FeCl3:
acidic;
Fe3+ ion attracts electrons in OH bonds of water ligands releasing H + ions
(due to high charge density) / OWTTE;
Accept suitable equations such as [Fe(H2O)6]3+  [Fe(H2O)5(OH)]2+ + H+
/ [Fe(H2O)6]3+ + H2O  [Fe(H2O)5(OH)]2+ + H3O+ for M2.
Accept equations indicating the formation of [Fe(H2O)4(OH)2]+,
[Fe(H2O)3(OH)3], [Fe(H2O)2(OH)4]–.
Do not penalize → .
M2 can only be awarded if M1 correct.
CH3CH2NH3NO3 :
acidic;
CH 3CH 2 NH 3+ is conjugate acid of weak base, CH 3CH 2 NH 2 so acidic and
NO3– is conjugate base of strong acid, HNO3 , so pH-neutral / salt of a weak
base and a strong acid / OWTTE;
M4 can only be awarded if M3 correct.
Do not allow the salt produces a strong acid and weak base in solution.
(ii)
acidic;
K a (NH 4 + ) > K b (F− ) / pK a (NH 4 + ) < pK b (F− ) ;
M2 can only be awarded if M1 correct but award [1max] for neutral as salt
of weak acid and weak base.
[4]
[2]
– 15 –
7.
(a)
increase (in oxidation number);
(b)
(i)
M13/4/CHEMI/HP2/ENG/TZ2/XX/M
[1]
Cu (s) + 2NO3− (aq) + 4H + (aq) → Cu 2+ (aq) + 2NO 2 (g) + 2H 2O (l) /
Cu (s) + 2 HNO3 (aq) + 2H + (aq) → Cu 2+ + 2NO 2 (g) + 2H 2O (l) ;
correct reactants and products;
fully balanced chemical equation;
Ignore state symbols.
M1 can be scored if there are unbalanced electrons in equation.
M2 can only be scored if M1 is correct.
M2 can be scored if there are balanced electrons on both sides of equation.
(ii)
(c)
(i)
Oxidizing agent: NO3–/nitrate/HNO3/nitric acid and Reducing agent: Cu/
copper;
[2]
[1]
Diagram showing gas, solution and solid electrode;
For example,
H2 (g) at 100 kPa, 298 K
1 mol dm–3
H+ (aq)
Pt
1 mol dm −3 H + (aq) and Pt;
Allow 1 mol L–1 or 1 M.
Allow 1 mol dm–3 HCl (aq) or other source of 1mol dm −3 H + (aq) ions.
100 kPa/105 Pa/1 bar ( H 2 (g) pressure) and 298 K / 25 °C ;
Ignore state symbols throughout.
Allow 1.01 × 105 Pa/1 atm.
(ii)
potential of reduction half-reaction under standard conditions measured
relative to standard hydrogen electrode/SHE / potential under standard
conditions relative to standard hydrogen electrode/SHE;
Instead of standard conditions allow either solute concentration of
1 mol dm–3 or 100 kPa/105 Pa/1 bar (pressure) for gases (allow 1 atm).
Allow voltage/EMF instead of potential.
[3]
[1]
– 16 –
M13/4/CHEMI/HP2/ENG/TZ2/XX/M
(iii) Cu 2+ (aq) + H 2 (g) → Cu (s) + 2H + (aq)
reactants and products;
fully balanced chemical equation, including state symbols;
M2 cannot be scored if M1 is incorrect.
(d)
(i)
[2]
Voltaic cell showing:
V
Salt bridge
Sn
Cu
Cu2+ (aq)
Sn2+ (aq)
Labelled positive electrode (cathode): Cu 2+ /Cu and negative electrode
(anode): Sn 2+ /Sn ;
Do not penalize if state symbols are not included (since given in question).
voltmeter and salt bridge;
Voltmeter can be labelled or drawn as a circle with a V.
Allow ammeter/A.
Salt bridge can be labelled, represented with drawing connecting the two
half-cells, labelled as potassium nitrate or using its chemical formula
(for example, KNO3) etc.
(e)
correct direction of electron movement from Sn to Cu in external circuit;
[3]
(ii)
(+) 0.48 (V);
[1]
(i)
positive;
[1]
(ii)
provides ions (to carry current) / water poor conductor (of electricity);
Do not accept electrons instead of ions.
[1]
(iii) copper reacts so (nonreactive metal such as) Pt used;
Accept Ag, Au or any named metal less reactive than copper as electrode.
Do not accept Cu reacts with water or graphite as electrode.
[1]
(iv) Positive electrode (anode):
2H 2 O (l) → O 2 (g) + 4H + (aq) + 4e− / 4OH − (aq) → O 2 (g) + 2H 2 O (l) + 4e − ;
Negative electrode (cathode):
H + (aq) + e − → 12 H 2 (g) / 4H + (aq) + 4e− → 2H 2 (g) / 2H + (aq) + 2e − → H 2 /
2H 2 O (l) + 2e − → H 2 (g) + 2OH − (aq) / H 2 O (l) + e− → 12 H 2 (g) + OH − ;
Award [1 max] if M1 and M2 reversed.
[2]
– 17 –
M13/4/CHEMI/HP2/ENG/TZ2/XX/M
Ignore state symbols.
Allow e instead of e–.
Do not penalize use of equilibrium sign instead of → .
Accept a multiple of the equations.
(v)
2H 2 O (l) → 2H 2 (g) + O 2 (g) / H 2 O (l) → H 2 (g) + 12 O 2 (g) ;
State symbols required as asked for in question.
Do not penalize use of equilibrium sign instead of → .
Do not accept any multiple of 2H + (aq) + 2OH − (aq) → 2H 2 (g) + O2 (g) .
(vi)
+
+
–
–
electrolytic cell showing solid electrodes immersed in solution;
positive electrode (anode) connected to positive terminal of battery and
negative electrode (cathode) to negative terminal;
Allow graphite or metal given in e(iii) as electrodes.
(vii) bubbles /gas produced;
Do not accept hydrogen is formed at cathode and oxygen formed at anode.
(f)
[1]
[2]
[1]
 
100

−3
n(O 2 )  = 
  = 4.46 × 10 (mol) ;
  22.4 × 1000  
m ( = (4.46 × 10−3 × 2 × 207.19) ) = 1.85(g) ;
OR
 PV 
−3
n(O 2 )  =
 = 4.45 × 10 (mol) ;
 RT 
m ( = 4.45 ×10−3 × 2 × 207.19 ) = 1.84 (g) ;
[2]
– 18 –
8.
(a)
M13/4/CHEMI/HP2/ENG/TZ2/XX/M
compounds with same structural formula but different arrangements of atoms in
space;
Award [1] if correct description of geometric and optical isomers given.
[1]
(b)
1: sp2 and 2: sp3 ;
[1]
(c)
amine;
benzene ring;
Allow phenyl (group).
Do not allow just benzene.
alkene / chloroalkene;
chloro;
ether / phenyl ether;
Ethers not required as per guide but allow if given.
(d)
(i)
H
[1 max]
H
C
C
H3C
;
CH3
;
H
CH3
C
C
;
H
CH3
;
H
H
H
C
C
H
CH3
C
H
;
[2 max]
– 19 –
(ii)
M13/4/CHEMI/HP2/ENG/TZ2/XX/M
trans-but-2-ene and cis-but-2-ene;
Allow trans 2-butene and cis 2-butene.
Do not accept just 2-butene or 2-butene.
but-1-ene;
Allow 1-butene.
(iii) Q: CH3CHBrCH 2 CH3 ;
R: CH 3CH (OH)CH 2 CH3 ;
S: CH 3CHBrCHBrCH 3 ;
T: CH3CH (OH)CH 2 CH 3 ;
Condensed or full structural formulas may be given.
[2]
[4]
– 20 –
M13/4/CHEMI/HP2/ENG/TZ2/XX/M
(iv) Since secondary bromoalkane could be either SN1 and SN2 so allow SN1 or
SN2 for M1 –M4.
SN1:
curly arrow showing Br leaving;
Do not allow arrow originating from C to C–Br bond.
representation of secondary carbocation;
curly arrow going from lone pair/negative charge on O in HO − to C+ ;
Do not allow arrow originating on H in OH–.
formation of CH 3CH(OH)CH 2 CH 3 and Br − ;
Allow formation of NaBr instead of Br–.
OR
SN2:
curly arrow going from lone pair/negative charge on O in HO − to C;
Do not allow curly arrow originating on H in OH–.
curly arrow showing Br leaving;
Accept curly arrow either going from bond between C and Br to Br in
2-bromobutane or in the transition state.
Do not allow arrow originating from C to C–Br bond.
– 21 –
M13/4/CHEMI/HP2/ENG/TZ2/XX/M
representation of transition state showing negative charge, square brackets
and partial bonds;
Do not penalize if HO and Br are not at 180  to each other.
Do not award M3 if OH—C bond is represented.
formation of CH 3CH(OH)CH 2 CH 3 and Br − ;
Allow formation of NaBr instead of Br–.
[4]
H3CCOCH 2CH 3 ;
Condensed or full structural formula may be given.
[1]
(vi) butan-2-one;
Allow 2-butanone or butanone.
Accept butan-2-one if (v) is incorrect but also apply ECF.
[1]
(v)
(e)
(i)
mC : (1.755 × 10−1 × 12.01) / (44.01) = 4.790 × 10−2 g and
mH : (7.187 × 10 −2 × 2 × 1.01) / (18.02) = 8.056 × 10−3 g ;
mO : (6.234 × 10−2 − 8.056 × 10−3 − 4.790 ×10−2 ) = 6.384 ×10−3 g ;
(nC = 3.988 ×10−3 and nH = 2 × 3.988 ×10−3 and nO = 3.988 ×10−3 hence
empirical formula =) C10 H 20 O ;
( M (C
10
H 20 O) = 156.30 (g mol −1 ), therefore molecular formula = ) C10 H 20 O ;
OR
 1.755 ×10−1 
 7.187 × 10−1 
−3
−3
nCO 2 = 
 = 3.988 × 10 and nH2O = 
 = 3.988 ×10 ;
 44.01 
 18.02 
mO : (6.234 × 10−2 − 8.056 × 10−3 − 4.790 ×10−2 ) = 6.384 ×10−3 g ;
(nC = 3.988 ×10−3 and nH = 2 × 3.988 ×10−3 and nO = 3.988 ×10−3 hence
empirical formula =) C10 H 20 O ;
( M (C
10
H 20 O) = 156.30 (g mol−1 ), therefore molecular formula = ) C10 H 20 O ;
[4]
Allow alternative working to be used.
Award [3 max] for C10H20O if no working shown.
(ii)
chiral (carbon/centre/atom) / (tetrahedral) carbon surrounded by four
different groups;
Accept chiral compound or chiral molecule.
(iii) polarimeter and (enantiomers) rotate plane of polarized light in (equal and)
opposite directions;
[1]
[1]
– 22 –
M13/4/CHEMI/HP2/ENG/TZ2/XX/M
(iv) Physical properties:
identical except for rotation of plane polarized light;
Accept “identical” as different optical properties assessed in (iii).
Do not accept similar.
Chemical properties:
identical unless they interact with other optically active/chiral
compounds/reagents/solvents / identical with achiral compounds/reagents
/solvents / OWTTE;
Allow different physiological effects/taste.
[2]
N13/4/CHEMI/HPM/ENG/TZ0/XX
88136101
CHEMISTRY
Higher level
Paper 1
Monday 18 November 2013 (afternoon)
1 hour
INSTRUCTIONS TO CANDIDATES
• Do not open this examination paper until instructed to do so.
• Answer all the questions.
• For each question, choose the answer you consider to be the best and indicate your choice on
the answer sheet provided.
• The periodic table is provided for reference on page 2 of this examination paper.
• The maximum mark for this examination paper is [40 marks].
8813-6101
17 pages
© International Baccalaureate Organization 2013
8813-6101
23
V
50.94
87
Fr
(223)
88
Ra
(226)
‡
†
89 ‡
Ac
(227)
90
Th
232.04
58
Ce
140.12
91
Pa
231.04
59
Pr
140.91
73
Ta
180.95
38
Sr
87.62
37
Rb
85.47
22
Ti
47.90
56
57 †
72
55
Ba
La
Cs
Hf
132.91 137.34 138.91 178.49
20
Ca
40.08
19
K
39.10
41
Nb
92.91
39
Y
88.91
12
Mg
24.31
11
Na
22.99
92
U
238.03
60
Nd
144.24
74
W
183.85
42
Mo
95.94
24
Cr
52.00
Relative atomic mass
Element
Atomic number
40
Zr
91.22
21
Sc
44.96
4
Be
9.01
2
3
Li
6.94
1
H
1.01
1
30
Zn
65.37
93
Np
(237)
94
Pu
(242)
95
Am
(243)
96
Cm
(247)
97
Bk
(247)
98
Cf
(251)
61
66
62
63
64
65
Pm
Dy
Sm
Tb
Eu
Gd
146.92 150.35 151.96 157.25 158.92 162.50
75
80
76
77
78
79
Re
Os
Pt
Au
Hg
Ir
186.21 190.21 192.22 195.09 196.97 200.59
48
44
45
46
47
Cd
Ru
Rh
Pd
Ag
101.07 102.91 106.42 107.87 112.40
29
Cu
63.55
43
Tc
98.91
28
Ni
58.71
26
Fe
55.85
25
Mn
54.94
27
Co
58.93
The Periodic Table
50
Sn
118.69
32
Ge
72.59
14
Si
28.09
6
C
12.01
4
99
Es
(254)
100
Fm
(257)
67
68
Ho
Er
164.93 167.26
81
82
Tl
Pb
204.37 207.19
49
In
114.82
31
Ga
69.72
13
Al
26.98
5
B
10.81
3
101
Md
(258)
69
Tm
168.93
83
Bi
208.98
51
Sb
121.75
33
As
74.92
15
P
30.97
7
N
14.01
5
35
Br
79.90
17
Cl
35.45
9
F
19.00
7
85
At
(210)
102
No
(259)
103
Lr
(260)
70
71
Lu
Yb
173.04 174.97
84
Po
(210)
52
53
Te
I
127.60 126.90
34
Se
78.96
16
S
32.06
8
O
16.00
6
86
Rn
(222)
54
Xe
131.30
36
Kr
83.80
18
Ar
39.95
10
Ne
20.18
2
He
4.00
0
–2–
N13/4/CHEMI/HPM/ENG/TZ0/XX
–3–
1.
2.
N13/4/CHEMI/HPM/ENG/TZ0/XX
What is the total number of oxygen atoms in 0.200 mol of glucose, C6H12O6 ?
A.
1.20
B.
6.00
C.
1.20×1023
D.
7.22×1023
What are the coefficients of H2SO4 (aq) and H3PO4 (aq) when the following equation is balanced
using the smallest possible whole numbers?
___ Ca 3 (PO 4 ) 2 (s) + ___ H 2SO 4 (aq) → ___ CaSO 4 (s) + ___ H 3PO 4 (aq)
3.
Coefficient of
H2SO4 (aq)
Coefficient of
H3PO4 (aq)
A.
1
2
B.
2
3
C.
3
1
D.
3
2
7.102 g of Na 2SO 4 ( M = 142.04 g mol−1 ) is dissolved in water to prepare 0.5000 dm3 of solution. What is the concentration of Na2SO4 in mol dm–3?
A.
2.500×10–2
B.
1.000×10–1
C.
1.000×10
D.
1.000×102
8813-6101
Turn over
–4–
4.
5.
6.
N13/4/CHEMI/HPM/ENG/TZ0/XX
What are the numbers of neutrons and electrons in the iodine ion, 125I+?
Neutrons
Electrons
A.
53
53
B.
72
52
C.
72
53
D.
125
52
What is the abbreviated electron configuration of the telluride ion, Te2–?
A.
[Kr]5s25d105p6
B.
[Kr]5s24d105p2
C.
[Kr]5s24d105p4
D.
[Kr]5s24d105p6
Which series is arranged in order of increasing radius?
A.
F < Cl− < Cl
B.
Rb < K < Na
C.
Al3+ < Mg 2+ < Na +
D.
I − < Br − < Cl−
8813-6101
–5–
7.
8.
9.
N13/4/CHEMI/HPM/ENG/TZ0/XX
Which oxides form acidic solutions when added to water?
A.
P4O10(s) and SO3(g)
B.
Na2O (s) and MgO (s)
C.
Al2O3(s) and SiO2(s)
D.
MgO (s) and Al2O3(s)
Which compound is likely to be colourless?
A.
[Zn(H2O)6]Cl2
B.
[NH4]2[Fe(H2O)6][SO4]2
C.
K3[Co(CN)6]
D.
[Ni(NH3)6][BF4]2
What is the formula of calcium nitride?
A.
Ca3N2
B.
Ca2N3
C.
Ca(NO2)2
D.
Ca(NO3)2
8813-6101
Turn over
–6–
10.
11.
12.
N13/4/CHEMI/HPM/ENG/TZ0/XX
Which compounds have an ionic lattice structure in the solid state?
I.
Silicon dioxide
II.
Sodium fluoride
III.
Ammonium nitrate
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
Which intermolecular forces exist between the following molecules?
H2Se
CO
H2
A.
van der Waals’ and dipole-dipole
van der Waals’ and
dipole-dipole
van der Waals’ only
B.
van der Waals’, dipole-dipole
and hydrogen bonding
van der Waals’ only
van der Waals’ and
hydrogen bonding
C.
van der Waals’, dipole-dipole
and hydrogen bonding
van der Waals’ and
dipole-dipole
van der Waals’ only
D.
van der Waals’ and dipole-dipole
van der Waals’ and
dipole-dipole
van der Waals’ and
hydrogen bonding
Which species have dative covalent bonding?
I.
[Fe (H2O)6]Cl3
II.
NH4+
III.
H2O
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
8813-6101
–7–
13.
14.
N13/4/CHEMI/HPM/ENG/TZ0/XX
How many sigma (σ) and pi (π) bonds are there in CH3CH2CCCH2COOH?
A.
13σ and 5π
B.
15σ and 2π
C.
15σ and 3π
D.
15σ only
What is the hybridization of atoms X, Y and Z in epinephrine?
Y
O
H
H
O
C
H
O
H
H
C
H
Z
H
N
C
H
H
H
X
X
Y
Z
A.
sp2
sp3
sp3
B.
sp2
sp
sp3
C.
sp3
sp2
sp2
D.
sp3
sp3
sp3
8813-6101
Turn over
–8–
15.
16.
N13/4/CHEMI/HPM/ENG/TZ0/XX
Which processes are exothermic?
I.
CH 3CH 2 CH 3 (g) + 5O 2 (g) → 3CO 2 (g) + 4H 2 O (g)
II.
Cl2 (g) → 2Cl (g)
III.
CH 3CH 2 COOH (aq) + NaOH (aq) → CH 3CH 2 COONa (aq) + H 2 O (l)
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
Consider the following two equations.
2Ca (s) + O 2 (g) → 2CaO (s)
∆H Ö = + x kJ
Ca (s) + 0.5O 2 (g) + CO 2 (g) → CaCO3 (s)
∆H Ö = + y kJ
What is ∆H Ö, in kJ, for the following reaction?
CaO (s) + CO 2 (g) → CaCO3 (s)
A.
y – 0.5x
B.
y–x
C.
0.5 – y
D.
x–y
8813-6101
–9–
17.
18.
19.
N13/4/CHEMI/HPM/ENG/TZ0/XX
Which ionic compound has the most endothermic lattice enthalpy?
A.
Sodium chloride
B.
Sodium oxide
C.
Magnesium chloride
D.
Magnesium oxide
Which processes are predicted to have a positive entropy change, ∆S ?
I.
I 2 (g) → I 2 (s)
II.
4NH 3 (g) + 5O 2 (g) → 4NO (g) + 6H 2 O (g)
III.
CH 3OH (l) → CH 3OH (g)
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
Which combination of ∆H and ∆S signs will always result in a spontaneous reaction at all
temperatures?
∆H
∆S
A.
+
+
B.
+
–
C.
–
–
D.
–
+
8813-6101
Turn over
– 10 –
20.
N13/4/CHEMI/HPM/ENG/TZ0/XX
The diagram below shows the energy changes for a reaction with and without a catalyst.
Which symbols represent the activation energy, Ea , and the enthalpy change, ∆H , for the reaction
with a catalyst?
Energy
y
x
Reactants
z
Products
Extent of reaction
Ea (with a catalyst)
∆H
A.
x
z
B.
y
z
C.
z
x
D.
y–x
z
8813-6101
– 11 –
21.
N13/4/CHEMI/HPM/ENG/TZ0/XX
The following experimental rate data were obtained for a reaction carried out at temperature T.
A (g) + B(g) → C (g) + D (g)
Initial [A (g)] / mol dm–3
Initial [B (g)] / mol dm–3
Initial rate / mol dm–3 s–1
3.00×10–1
2.00×10–1
1.89×10–2
3.00×10–1
4.00×10–1
1.89×10–2
6.00×10–1
4.00×10–1
7.56×10–2
What are the orders with respect to A (g) and B (g)?
22.
Order with respect to A (g)
Order with respect to B (g)
A.
zero
second
B.
first
zero
C.
second
zero
D.
second
first
Consider the following proposed two-step reaction mechanism at temperature T.
k
Step 1:
1
2NO 2 (g) 
→ NO (g) + NO3 (g)
Step 2:
2
NO3 (g) + CO (g) 
→ NO 2 (g) + CO 2 (g)
k
Slow
Fast
Which statements are correct?
I.
The overall reaction is NO 2 (g) + CO (g) → NO (g) + CO 2 (g) .
II.
Step 1 is the rate-determining step of the reaction.
III.
The rate expression for Step 1 is rate = k1[NO 2 ]2.
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
8813-6101
Turn over
– 12 –
23.
Which of the following will shift the position of equilibrium to the right in the Haber process?
N 2 (g) + 3H 2 (g) 2NH 3 (g)
24.
25.
N13/4/CHEMI/HPM/ENG/TZ0/XX
I.
Decreasing the concentration of NH3(g)
II.
Decreasing the temperature
III.
Increasing the pressure
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
∆H Ö = −92.6 kJ
Which compound has the highest molar enthalpy of vaporization?
A.
Ethane
B.
Ethanoic acid
C.
Propane
D.
Propanoic acid
What are the conjugate acid–base pairs in the following reaction?
HCO3− (aq) + H 2 O (l) OH − (aq) + H 2 CO3 (aq)
Brønsted–Lowry
acid
Brønsted–Lowry
base
Conjugate acid
Conjugate base
A.
HCO3– (aq)
H2O (l)
H2CO3 (aq)
OH– (aq)
B.
H2CO3 (aq)
OH– (aq)
HCO3– (aq)
H2O (l)
C.
H2O (l)
HCO3– (aq)
H2CO3 (aq)
OH– (aq)
D.
H2O (l)
HCO3– (aq)
OH– (aq)
H2CO3 (aq)
8813-6101
– 13 –
26.
27.
28.
N13/4/CHEMI/HPM/ENG/TZ0/XX
Which group of three compounds contains only weak acids and bases?
A.
Ba (OH)2
CH3NH2
CH3COOH
B.
CH3CH2CH2COOH
CH3CH2NH2
HCOOH
C.
NH3
HNO3
CH3CH2COOH
D.
NH3
NaOH
H2CO3
What is the relationship between pKa , pKb and pKw for a conjugate acid–base pair?
A.
pK a = pK w + pK b
B.
pK a = pK w − pK b
C.
pK a × pK b = pK w
D.
pK a
= pK w
pK b
The table below shows data for the Ka and pKb values for some acids and bases at 298 K.
Acid
Ka
Base
pKb
HClO
2.9×10–8
NH3
4.75
C6H5CH2COOH
4.9×10–5
C6H5NH2
9.13
Which two formulas represent the weakest acid and the weakest base in the table?
A.
HClO and C6H5NH2
B.
C6H5CH2COOH and NH3
C.
C6H5CH2COOH and C6H5NH2
D.
HClO and NH3
8813-6101
Turn over
– 14 –
29.
30.
31.
N13/4/CHEMI/HPM/ENG/TZ0/XX
Which pair of compounds could be used to make a buffer solution (assuming appropriate
molar ratios)?
A.
KCl and HCl
B.
NaCl and HCl
C.
KHSO4 and H2SO4
D.
CH3COONa and CH3COOH
Which salts form acidic solutions when dissolved in water?
I.
NH4Cl
II.
Cr (NO3)3
III.
CH3COONa
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
What is the name of MnO2?
A.
Manganese(II) oxide
B.
Magnesium(II) oxide
C.
Manganese(IV) oxide
D.
Magnesium(IV) oxide
8813-6101
– 15 –
32.
N13/4/CHEMI/HPM/ENG/TZ0/XX
Consider the following reaction.
2Cr (OH)3 (s) + 6ClO − (aq) → 2CrO 4 2− (aq) + 3Cl2 (g) + 2OH − (aq) + 2H 2 O (l)
Which statement is correct?
33.
A.
Cr (OH)3 is the oxidizing agent and the oxidation number of chromium changes from +3 to +6.
B.
Cr (OH)3 is the reducing agent and undergoes reduction.
C.
ClO– is the oxidizing agent and the oxidation number of chlorine changes from +1 to 0.
D.
ClO– is the reducing agent and the oxidation number of chlorine changes from –1 to 0.
Consider the following two standard electrode potentials at 298 K.
Sn 2+ (aq) + 2e − Sn (s)
E Ö = −0.14 V
Fe3+ (aq) + e − Fe 2+ (aq)
E Ö = +0.77 V
What is the equation and cell potential for the spontaneous reaction that occurs?
34.
A.
2Fe 2+ (aq) + Sn 2+ (aq) → 2Fe3+ (aq) + Sn (s)
E Ö = −0.91V
B.
2Fe3+ (aq) + Sn (s) → 2Fe 2+ (aq) + Sn 2+ (aq)
E Ö = +0.91V
C.
2Fe 2+ (aq) + Sn 2+ (aq) → 2Fe3+ (aq) + Sn (s)
E Ö = +0.91V
D.
2Fe3+ (aq) + Sn (s) → 2Fe 2+ (aq) + Sn 2+ (aq)
E Ö = +1.68 V
What happens during the electrolysis of concentrated aqueous potassium chloride?
I.
Reduction takes place at the negative electrode (cathode).
II.
Hydrogen gas is evolved at the negative electrode (cathode).
III.
The pH of the electrolyte increases.
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
8813-6101
Turn over
– 16 –
35.
36.
37.
38.
N13/4/CHEMI/HPM/ENG/TZ0/XX
What is the name of (CH3)3CCOCH3 , applying IUPAC rules?
A.
2,2-dimethylbutan-3-one
B.
3,3-dimethylbutan-2-one
C.
2,2-dimethylbutanal
D.
3,3-dimethylbutanal
Which functional groups are present in C6H5CONHC6H5?
A.
Benzene ring (phenyl), amine
B.
Benzene ring (phenyl), ketone, amine
C.
Benzene ring (phenyl), amide
D.
Alkene, amide
What is the product of the reaction when CH3CH2CH2CH2CH2CN is reduced by hydrogen, using a
nickel catalyst under the appropriate conditions?
A.
CH3CH2CH2CH2CH2NH2
B.
CH3CH2CH2CH2CH2CH2NH2
C.
CH3CH2CH2CH2CH2CH3
D.
CH3CH2CH2CH2CH2CH2CH3
What is the major organic product formed from the reaction of (CH3)3CBr with a concentrated,
ethanolic solution of KOH?
A.
(CH3)3COH
B.
(CH3)2CCH2
C.
(CH3)2CO
D.
(CH3)2CHO
8813-6101
– 17 –
39.
40.
N13/4/CHEMI/HPM/ENG/TZ0/XX
What is the organic product of the reaction between butan-1-ol and ethanoic acid on heating using
concentrated sulfuric acid?
A.
Butyl methanoate
B.
Butyl ethanoate
C.
Ethyl butanoate
D.
Ethyl propanoate
A student measured the mass and volume of a piece of silver and recorded the following values.
Mass of empty weighing bottle
1.0800 g
Mass of weighing bottle with piece of silver
11.5700 g
Volume of silver
1.00 cm3
Which value, in g cm–3, for the density of silver should the student report in her laboratory notebook?
A.
10.49
B.
10.4900
C.
10.5
D.
10.500
8813-6101
N13/4/CHEMI/HPM/ENG/TZ0/XX/M
MARKSCHEME
November 2013
CHEMISTRY
Higher Level
Paper 1
2 pages
–2–
N13/4/CHEMI/HPM/ENG/TZ0/XX/M
1.
D
16.
A
31.
C
46.
–
2.
D
17.
D
32.
C
47.
–
3.
B
18.
C
33.
B
48.
–
4.
B
19.
D
34.
D
49.
–
5.
D
20.
A
35.
B
50.
–
6.
C
21.
C
36.
C
51.
–
7.
A
22.
D
37.
B
52.
–
8.
A
23.
D
38.
B
53.
–
9.
A
24.
D
39.
B
54.
–
10.
C
25.
C
40.
C
55.
–
11.
A
26.
B
41.
–
56.
–
12.
A
27.
B
42.
–
57.
–
13.
C
28.
A
43.
–
58.
–
14.
A
29.
D
44.
–
59.
–
15.
B
30.
A
45.
–
60.
–
N13/4/CHEMI/HP2/ENG/TZ0/XX
88136102
CHEMISTRY
HIGHER level
Paper 2
Candidate session number
0
0
Examination code
Monday 18 November 2013 (afternoon)
8
2 hours 15 minutes
8
1
3
–
6
1
0
2
INSTRUCTIONS TO CANDIDATES
•
•
•
•
•
•
•
•
Write your session number in the boxes above.
Do not open this examination paper until instructed to do so.
Section A: answer all questions.
Section B:answer two questions.
Write your answers in the boxes provided.
A calculator is required for this paper.
A clean copy of the Chemistry Data Booklet is required for this paper.
The maximum mark for this examination paper is [90 marks].
31 pages
© International Baccalaureate Organization 2013
32EP01
–2–
N13/4/CHEMI/HP2/ENG/TZ0/XX
Section a
Answer all questions. Write your answers in the boxes provided.
1.
Reaction kinetics can be investigated using the iodine clock reaction. The equations for two
reactions that occur are given below.
Reaction A:
H 2 O 2 (aq) + 2I − (aq) + 2H + (aq) → I 2 (aq) + 2H 2 O (l)
Reaction B:
I 2 (aq) + 2S2 O32− (aq) → 2I − (aq) + S4 O6 2− (aq)
Reaction B is much faster than reaction A, so the iodine, I2, formed in reaction A immediately
reacts with thiosulfate ions, S2O32–, in reaction B, before it can react with starch to form the
familiar blue-black, starch-iodine complex.
In one experiment the reaction mixture contained:
5.0 ± 0.1 cm3 of 2.00 mol dm–3 hydrogen peroxide (H2O2)
5.0 ± 0.1 cm3 of 1 % aqueous starch
20.0 ± 0.1 cm3 of 1.00 mol dm–3 sulfuric acid (H2SO4)
20.0 ± 0.1 cm3 of 0.0100 mol dm–3 sodium thiosulfate (Na2S2O3)
50.0 ± 0.1 cm3 of water with 0.0200 ± 0.0001 g of potassium iodide (KI) dissolved in it.
After 45 seconds this mixture suddenly changed from colourless to blue-black.
(a)
The concentration of iodide ions, I–, is assumed to be constant. Outline why this is a
valid assumption.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
For this mixture the concentration of hydrogen peroxide, H2O2, can also be assumed to
be constant. Explain why this is a valid assumption.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
32EP02
–3–
N13/4/CHEMI/HP2/ENG/TZ0/XX
(Question 1 continued)
(c)
[2]
Explain why the solution suddenly changes colour.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (d)
(i)
Calculate the total uncertainty, in cm3, of the volume of the reaction mixture.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Calculate the percentage uncertainty of the concentration of potassium iodide
solution added to the overall reaction mixture.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) Determine the percentage uncertainty in the concentration of potassium iodide in
the final reaction solution.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
32EP03
–4–
N13/4/CHEMI/HP2/ENG/TZ0/XX
(Question 1 continued)
(e)
The colour change occurs when 1.00 × 10–4 mol of iodine has been formed. Use the
total volume of the solution and the time taken, to calculate the rate of the reaction,
including appropriate units.
[4]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (f)
The activation energy can be determined using the Arrhenius equation, which is given in
Table 1 of the Data Booklet. The experiment was carried out at five different temperatures. An incomplete graph to determine the activation energy of the reaction, based on
these results, is shown below. 2.8 × 10–3
0
2.9 × 10–3 3.0 × 10–3
3.1 × 10–3
3.2 × 10–3 3.3 × 10–3
3.4 × 10–3 3.5 × 10–3
–1
–2
–3
–4
–5
(This question continues on the following page)
32EP04
–5–
N13/4/CHEMI/HP2/ENG/TZ0/XX
(Question 1 continued)
(i)
[2]
State the labels for each axis.
x-axis:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . y-axis:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Use the graph to determine the activation energy of the reaction, in kJ mol–1,
correct to three significant figures.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (g)
In another experiment, 0.100 g of a black powder was also added while all other
concentrations and volumes remained unchanged. The time taken for the solution to
change colour was now 20 seconds. Outline why you think the colour change occurred
more rapidly and how you could confirm your hypothesis.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
32EP05
–6–
2.
N13/4/CHEMI/HP2/ENG/TZ0/XX
Consider the two-stage reaction pathway below.
ClCH2
CH2Cl
I
II
X
HOOC
COOH
(a)
Deduce the structural formula of compound X.
[1]
(b)
State the reagents and conditions required for stage II of the pathway.
[2]
Reagents:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conditions:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
32EP06
–7–
N13/4/CHEMI/HP2/ENG/TZ0/XX
(Question 2 continued)
(c)
The final product can react with ethane-1,2-diol, HOCH2–CH2OH, to produce a polymer. (i)
[1]
State the type of polymerization involved.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Draw the structure of a section of the polymer produced containing two molecules
of each monomer.
[1]
Turn over
32EP07
–8–
3.
N13/4/CHEMI/HP2/ENG/TZ0/XX
Calcium nitrate contains both covalent and ionic bonds.
(a)
(i)
State the formula of both ions present and the nature of the force between
these ions.
[2]
Ions:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nature of force:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
State which atoms are covalently bonded.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
Bonding in the nitrate ion involves electron delocalization. Explain the meaning of
electron delocalization and how it affects the ion.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
32EP08
–9–
N13/4/CHEMI/HP2/ENG/TZ0/XX
(Question 3 continued)
(c)
Nitrogen also forms oxides, which are atmospheric pollutants.
(i)
[1]
Outline the source of these oxides.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
State one product formed from their reaction with water.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) State one environmental problem caused by these atmospheric pollutants.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
32EP09
– 10 –
4.
N13/4/CHEMI/HP2/ENG/TZ0/XX
EUK-134, the structure of which is shown below, is a complex ion of manganese(III) that is
used in expensive sun-protection products because of its powerful antioxidant properties.
N
N
Mn
O
Cl
H3CO
OCH3
(a)
O
State the electron configuration of the manganese ion in EUK-134.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
State the name given to species that bond to a central metal ion, and identify the type
of bond present.
[2]
Name given:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Type of bond:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (c)
Transition metals have certain characteristic properties. State two properties that are
involved in EUK-134 rapidly decreasing the concentration of oxidizing agents.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
32EP10
– 11 –
N13/4/CHEMI/HP2/ENG/TZ0/XX
(Question 4 continued)
(d)
Substances like EUK-134 are often coloured. Explain why compounds of transition
metals absorb visible radiation.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
32EP11
– 12 –
N13/4/CHEMI/HP2/ENG/TZ0/XX
Section b
Answer two questions. Write your answers in the boxes provided.
5.
In December 2010, researchers in Sweden announced the synthesis of N,N–dinitronitramide,
N(NO2)3. They speculated that this compound, more commonly called trinitramide, may have
significant potential as an environmentally friendly rocket fuel oxidant.
(a)
Methanol reacts with trinitramide to form nitrogen, carbon dioxide and water. Deduce
the coefficients required to balance the equation for this reaction.
[1]
___ N(NO 2 )3 (g) + ___ CH 3OH (l) → ___ N 2 (g) + ___ CO 2 (g) + ___ H 2 O (l)
(b)
Suggest one reason why trinitramide might be more environmentally friendly than other
rocket fuel oxidants such as ammonium perchlorate (NH4ClO4).
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
32EP12
– 13 –
N13/4/CHEMI/HP2/ENG/TZ0/XX
(Question 5 continued)
(c)
Calculate the enthalpy change, in kJ mol–1, when one mole of trinitramide
decomposes to its elements, using bond enthalpy data from Table 10 of the Data Booklet. Assume that all the N–O bonds in this molecule have a bond enthalpy of 305 kJ mol–1.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (d)
The entropy change, ∆S , for the decomposition of trinitramide has been estimated as
+700 J K −1 mol−1. Comment on the sign of ∆S .
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
32EP13
– 14 –
N13/4/CHEMI/HP2/ENG/TZ0/XX
(Question 5 continued)
(e)
Using +700 J K −1 mol−1 as the value for the entropy change, along with your answer to
part (c), calculate ∆G, in kJ mol–1, for this reaction at 300 K. (If you did not obtain an
answer for part (c), then use the value –1000 kJ mol–1, but this is not the correct value.)
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (f)
Explain how changing the temperature will affect whether or not the decomposition of
trinitramide is spontaneous.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (g)
Outline how the length of the N–N bond in trinitramide compares with the N–N bond in
nitrogen gas, N2.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
32EP14
– 15 –
N13/4/CHEMI/HP2/ENG/TZ0/XX
(Question 5 continued)
(h)
[3]
Deduce the N–N–N bond angle in trinitramide and explain your reasoning.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (i)
[2]
Predict, with an explanation, the polarity of the trinitramide molecule.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The normal boiling point of a liquid is the temperature at which its vapour pressure is
equal to standard atmospheric pressure (101.3 kPa). On the axes provided, sketch a
graph showing how the vapour pressure of water varies with temperature and state its
boiling point at 101.3 kPa.
Vapour pressure / kPa
(j)
[2]
101.3
Temperature / °C
(This question continues on the following page)
Turn over
32EP15
– 16 –
N13/4/CHEMI/HP2/ENG/TZ0/XX
(Question 5 continued)
(k)
Outline why the boiling point of water is lower in places well above sea level, where the
atmospheric pressure is considerably below 101.3 kPa.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (l)
Describe the equilibrium that exists between a liquid and its vapour and how, in terms
of kinetic theory, this is affected by an increase in temperature.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32EP16
[3]
– 17 –
6.
N13/4/CHEMI/HP2/ENG/TZ0/XX
In acidic solution, ions containing titanium can react according to the half-equation below.
TiO 2+ (aq) + 2H + (aq) + e −  Ti3+ (aq) + H 2 O (l)
(a)
E Ö = −0.06 V
Define the term standard electrode potential, E Ö .
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
(i)
State the initial and final oxidation numbers of titanium and hence deduce
whether it is oxidized or reduced in this change.
Initial oxidation
number
(ii)
Final oxidation
number
[2]
Oxidized / reduced
Considering the above equilibrium, predict, giving a reason, how adding more
acid would affect the strength of the TiO2+ ion as an oxidizing agent.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
32EP17
– 18 –
N13/4/CHEMI/HP2/ENG/TZ0/XX
(Question 6 continued)
(c)
In the two experiments below, predict whether a reaction would occur and deduce
an equation for any reaction that takes place. Refer to Table 14 of the Data Booklet
if necessary.
[3]
KI (aq) is added to a solution containing Ti3+(aq) ions:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Zn (s) is added to a solution containing TiO2+(aq) and H+(aq) ions:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
32EP18
– 19 –
N13/4/CHEMI/HP2/ENG/TZ0/XX
(Question 6 continued)
(d)
In the diagram below, A and B are inert electrodes and, in the aqueous solutions, all ions
have a concentration of 1 mol dm–3.
voltmeter
V
salt bridge
A
B
Fe3+ and Fe2+
(i)
TiO2+, H+ and Ti3+
Using Table 14 of the Data Booklet, state the balanced half-equation for the reaction
that occurs at electrode A and whether it involves oxidation or reduction.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
[1]
Calculate the cell potential in V.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) On the diagram above label with an arrow
• the direction of electron flow in the wire
• the direction in which the positive ions flow in the salt bridge.
[1]
(This question continues on the following page)
Turn over
32EP19
– 20 –
N13/4/CHEMI/HP2/ENG/TZ0/XX
(Question 6 continued)
(e)
Sodium, silicon and sulfur are elements in period 3 of the periodic table that all
form oxides.
(i)
Compare the properties of the three oxides by completing the table below.
Na2O
SiO2
[3]
SO2
Bonding type
Standard
state
Effect on pH
of water
(ii)
Sulfur dioxide is a significant contributor to acid deposition. Identify a major,
man-made source of this pollutant.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) As well as the oxide above, sodium forms a peroxide that contains the peroxide
ion, O22–. Draw the Lewis (electron dot) structure of the peroxide ion.
[2]
(This question continues on the following page)
32EP20
– 21 –
N13/4/CHEMI/HP2/ENG/TZ0/XX
(Question 6 continued)
(f)
Although carbon and silicon both belong to group 4 of the periodic table, carbon dioxide
and silicon dioxide are different in many ways.
(i)
Describe the differences in the hybridization of these group 4 elements and the
precise nature of the bonds that they form with the oxygen atoms.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Xenon, although a noble gas, forms an oxide, XeO2 , that has a structure related
to that of SiO2. Compare the geometry around the silicon atoms in SiO2
with the geometry around the xenon atoms in XeO2, using the valence shell
electron pair repulsion (VSEPR) theory.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (g)
Silicon also forms a tetrachloride, SiCl4. State the equation for the reaction of SiCl4
with water.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
32EP21
– 22 –
7.
N13/4/CHEMI/HP2/ENG/TZ0/XX
Antimony, Sb, forms a fluoride, SbF5.
(a)
State the element that you would expect to have chemical properties most similar to
those of antimony.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The equilibrium that occurs when antimony(V) fluoride is dissolved in liquid hydrogen
fluoride can be represented by the equation below.
SbF5 (s) + 2HF(l)  SbF6 − (sol) + H 2 F+ (sol)
(b)
(i)
Describe the relationship between SbF5 and SbF6– in terms of the Lewis theory
of acids.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Explain the behaviour of HF in terms of the Brønsted–Lowry theory of acids.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
32EP22
– 23 –
N13/4/CHEMI/HP2/ENG/TZ0/XX
(Question 7 continued)
(c)
Outline how the following factors account for the fact that HCl is a strong acid and HF
is a weak acid.
(i)
[1]
The strength of the hydrogen–halogen bond.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
The interaction between an undissociated hydrogen halide molecule and a water
molecule.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (d)
Some students were provided with a 0.100 mol dm–3 solution of a monobasic acid, HQ,
and given the problem of determining whether HQ was a weak acid or a strong acid.
(i)
Neelu and Charles decided to solve the problem by determining the volume of
0.100 mol dm–3 sodium hydroxide solution needed to neutralize 25.0 cm3 of the acid.
Outline whether this was a good choice.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
32EP23
– 24 –
N13/4/CHEMI/HP2/ENG/TZ0/XX
(Question 7 continued)
(ii)
Identify one indicator that could be used when titrating aqueous sodium hydroxide
with both a strong acid and a weak acid, and outline the reason for your choice.
[2]
Indicator:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reason:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) Neelu and Charles decided to compare the volume of sodium hydroxide
solution needed with those required by known 0.100 mol dm–3 strong and weak
acids. Unfortunately they chose sulfuric acid as the strong acid. Outline why this
was an unsuitable choice.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv) Francisco and Shamiso decided to measure the pH of the initial solution, HQ, and
they found that its pH was 3.7. Deduce, giving a reason, the strength (weak or
strong) of the acid HQ.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
32EP24
– 25 –
N13/4/CHEMI/HP2/ENG/TZ0/XX
(Question 7 continued)
(e)
The second problem set for the students was to determine the acid dissociation constant,
Ka, of the acid HQ and its pKa.
(i)
Explain how the pKa could be determined from a graph of pH against the volume
of 0.100 mol dm–3 sodium hydroxide added.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Francisco and Shamiso found that the pH of the initial 0.100 mol dm–3 solution
was 3.7. However, this reading was inaccurate because they forgot to wash the
pH probe. Calculate the pKa of HQ using the reading they obtained.
[4]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
32EP25
– 26 –
N13/4/CHEMI/HP2/ENG/TZ0/XX
(Question 7 continued)
(f)
Manu and Lisa decided to convert the acid into a buffer solution by partly
neutralizing it. They mixed 10.0 cm3 of 0.100 mol dm–3 sodium hydroxide
solution with 40.0 cm3 of the 0.100 mol dm–3 solution of HQ. Determine the
pH of the resulting solution, showing your working, given that the Ka of HQ is
1.80 × 10–5 mol dm–3.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32EP26
[5]
– 27 –
8.
N13/4/CHEMI/HP2/ENG/TZ0/XX
2-methylbutan-2-ol, (CH3)2C(OH)CH2CH3, is a liquid with a smell of camphor that was
formerly used as a sedative. One way of producing it starts with 2-methylbut-2-ene.
(a)
State the other substances required to convert 2-methylbut-2-ene to 2-methylbutan-2-ol.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
Explain whether you would expect 2-methylbutan-2-ol to react with acidified
potassium dichromate(VI).
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (c)
As well as 2-methylbutan-2-ol, the reaction also produces a small quantity of an
optically active isomer, X.
(i)
State what is meant by optical activity.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
[1]
State what optical activity indicates about the structure of the molecule.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
32EP27
– 28 –
N13/4/CHEMI/HP2/ENG/TZ0/XX
(Question 8 continued)
(iii) Optical activity can be detected using a polarimeter. Explain how this works.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv) Deduce the structural formula of X.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (d)
Explain why 2-methylbut-2-ene is less soluble in water than 2-methylbutan-2-ol.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
32EP28
– 29 –
N13/4/CHEMI/HP2/ENG/TZ0/XX
(Question 8 continued)
(e)
2-methylbutan-2-ol can also be produced by the hydrolysis of 2-chloro-2-methylbutane,
(CH3)2CClC2H5 , with aqueous sodium hydroxide.
(i)
Explain the mechanism of this reaction using curly arrows to represent the
movement of electron pairs.
[4]
(ii)
State the rate expression for this reaction and the units of the rate constant.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
32EP29
– 30 –
N13/4/CHEMI/HP2/ENG/TZ0/XX
(Question 8 continued)
(iii) Suggest why, for some other halogenoalkanes, this hydrolysis is much more
effective in alkaline rather than in neutral conditions.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (f)
2-chloro-2-methylbutane contains some molecules with a molar mass of approximately
106 g mol–1 and some with a molar mass of approximately 108 g mol–1.
(i)
Outline why there are molecules with different molar masses.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Suggest, with a reason, whether the molecules with different molar masses will
undergo hydrolysis at different rates.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
32EP30
– 31 –
N13/4/CHEMI/HP2/ENG/TZ0/XX
(Question 8 continued)
(g)
2-chloro-2-methylbutane can also be converted into compound Z by a two-stage reaction
via compound Y:
CH3
H2C
C
Cl
CH3
Y
CH3
H2C
C
CH2
NH2
CH3
CH3
CH3
Z
2-chloro-2-methylbutane
(i)
Draw the structure of Y.
[1]
(ii)
State the reagent and any catalyst required for both the formation of Y and the
conversion of Y into Z.
[3]
Formation of Y:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conversion of Y into Z:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32EP31
Please do not write on this page.
Answers written on this page
will not be marked.
32EP32
N13/4/CHEMI/HP2/ENG/TZ0/XX/M
MARKSCHEME
November 2013
CHEMISTRY
Higher Level
Paper 2
16 pages
–2–
N13/4/CHEMI/HP2/ENG/TZ0/XX/M
This markscheme is the property of the International
Baccalaureate and must not be reproduced or distributed to any
other person without the authorization of the IB Assessment
Centre.
–3–
N13/4/CHEMI/HP2/ENG/TZ0/XX/M
Subject Details: Chemistry HL Paper 2 Markscheme
Mark Allocation
Candidates are required to answer ALL questions in Section A [40 marks] and TWO questions in
Section B [2 x 25 marks]. Maximum total = [90 marks].
1.
A markscheme often has more marking points than the total allows. This is intentional.
2.
Each marking point has a separate line and the end is shown by means of a semicolon (;).
3.
An alternative answer or wording is indicated in the markscheme by a slash (/). Either wording can
be accepted.
4.
Words in brackets ( ) in the markscheme are not necessary to gain the mark.
5.
Words that are underlined are essential for the mark.
6.
The order of marking points does not have to be as in the markscheme, unless stated otherwise.
7.
If the candidate’s answer has the same “meaning” or can be clearly interpreted as being of
equivalent significance, detail and validity as that in the markscheme then award the mark.
Where this point is considered to be particularly relevant in a question it is emphasized by
OWTTE (or words to that effect).
8.
Remember that many candidates are writing in a second language. Effective communication is more
important than grammatical accuracy.
9.
Occasionally, a part of a question may require an answer that is required for subsequent
marking points. If an error is made in the first marking point then it should be penalized. However,
if the incorrect answer is used correctly in subsequent marking points then follow through marks
should be awarded. When marking, indicate this by adding ECF (error carried forward) on the
script.
10.
Do not penalize candidates for errors in units or significant figures, unless it is specifically referred
to in the markscheme.
11.
If a question specifically asks for the name of a substance, do not award a mark for a correct
formula unless directed otherwise in the markscheme. Similarly if the formula is specifically asked
for, unless directed otherwise in the markscheme, do not award a mark for a correct name.
12.
If a question asks for an equation for a reaction, a balanced symbol equation is usually expected; do
not award a mark for a word equation or an unbalanced equation unless directed otherwise in the
markscheme.
13.
Ignore missing or incorrect state symbols in an equation unless directed otherwise in the
markscheme.
–4–
N13/4/CHEMI/HP2/ENG/TZ0/XX/M
SECTION A
1.
(a)
(b)
KI/I–/potassium iodide/iodide (ion) (rapidly) reformed (in second stage of
reaction);
amount (in mol) of H2O2/hydrogen peroxide >> amount (in mol) Na2S2O3/S2O32–
/sodium thiosulfate/ thiosulfate (ion);
Accept amount (in mol) of H2O2/hydrogen peroxide >> amount (in mol) KI/I–
/potassium iodide/iodide (ion).
Accept “H2O2/hydrogen peroxide is in (large) excess/high concentration”.
(at end of reaction) [H2O2] is only slightly decreased/virtually unchanged;
(c)
[2]
(i)
(5 0.1)  ()0.5 (cm 3 ) ;
[1]
(ii)
(±) 0.7(%) ;
Comprises both mass of KI   0.5% and volume of KI   0.2% .
[1]
(iii) 0.5 0.7  ()1.2% ;
Sum of (i) and (ii) (percentage uncertainty of total volume = absolute
uncertainty as 100 cm3).
(e)
[2]
all Na2S2O3/sodium thiosulfate/S2O32–/thiosulfate consumed/used up;
Accept “iodine no longer converted to iodide”.
(free) iodine is formed / iodine reacts with starch / forms iodine-starch complex;
(d)
[1]
[1]
total volume  0.100 (dm3 ) /100 (cm3 ) ;
1.00 104
)1.00 103 (mol dm 3 ) ;
(change in concentration 
0.100
3


1.00 10
  2.2 105 ;
 rate 
45


Award [3] for the correct final answer.
mol dm 3 s 1 ;
[4]
–5–
(f)
(i)
N13/4/CHEMI/HP2/ENG/TZ0/XX/M
1
1
/ /T–1;
Temperature T
Ignore units.
x-axis:
y-axis: ln rate/loge rate / ln rate constant/loge rate constant / ln k/logek;
(ii)
gradient 
[2]
 Ea
;
R
4.00
4.80
 8276 ;
 8333 / 
3
3
(3.3110  2.83 10 )
(3.4110  2.83 103 )
 8.31 8333 
 8.31 8276 
1
1
[3]
Ea  
  69.3(kJ mol ) /  
  68.8(kJ mol ) ;
 1000 
 1000 
Award [3] for correct final answer.
Accept values from 65.0 to 73.0 kJ mol–1.
Deduct [1] for final answer in J mol–1.
Deduct [1] for final answer not to 3 significant figures.
gradient 
(g)
3
acting as a catalyst / black powder reacts with thiosulfate ions / solid dissolves to
give blue-black solution;
Accept any other valid suggestion which will make colour change more rapid.
For catalyst: amount/mass of black powder remains constant / no new/different
products formed / activation energy decreased;
For other suggestions: any appropriate way to test the hypothesis;
Award [1] for valid hypothesis, [1] for appropriate method of testing the stated
hypothesis.
[2 max]
–6–
2.
N13/4/CHEMI/HP2/ENG/TZ0/XX/M
(a)
;
[1]
Accept left hand end written as CH2(OH)–.
(b)
(c)
Reagents: acidified/H+ dichromate ion/Cr2O72–/potassium dichromate/K2Cr2O7/
sodium dichromate/Na2Cr2O7;
Accept acidified/H+ permanganate ion/MnO4–/potassium permanganate/KMnO4.
Conditions: reflux;
Accept “heat” (as the intermediate aldehyde will not be volatile enough to vaporize
significantly) unless distillation mentioned.
[2]
(i)
[1]
condensation;
(ii)
;
[1]
Extended bonds and two molecules of both monomers must be included.
Monomers can occur in the opposite order to that shown (glycerol part
on left).
Accept repeating units starting and ending at any point in the chain.
–7–
3.
(a)
(i)
(ii)
(b)
(c)
4.
N13/4/CHEMI/HP2/ENG/TZ0/XX/M
Ca2+ and NO3–;
electrostatic (attraction);
Do not accept ionic.
nitrogen/N and oxygen/O;
Do not accept nitrate/NO3–.
Accept atoms in nitrate/NO3–.
pi/-electrons shared by more than two atoms/nuclei / a pi/-bond/overlapping
p-orbitals that extends over more than two atoms/nuclei;
all (N–O) bonds equal length/strength/bond-order / charge on all oxygen/O atoms
equal / increases stability/lowers PE (of the ion);
Accept a diagram that clearly shows one or both points.
[2]
[1]
[2]
(i)
produced by high temperature combustion;
Accept combustion/jet/car engines / car exhaust/emissions / lightning / action
of bacteria/microorganisms.
Do not accept combustion/burning, cars, planes, jets, factories, power
plants etc.
[1]
(ii)
nitric acid/HNO3 / nitrous acid/nitric(III) acid/HNO2;
Accept “form acidic solutions / acid rain”.
[1]
(iii) acid deposition/rain / respiratory problems / corrosion problems /
decomposition of ozone layer / photochemical smog / acidification/pollution
of lakes / damage to plants/ trees;
Accept “acid rain” in either part (ii) or part (iii) but not both.
Do not accept air pollution.
[1]
(a)
1s22s22p63s23p63d4 / [Ar]3d4;
[1]
(b)
ligand;
dative/coordinate (covalent);
Do not accept “covalent”.
[2]
(c)
(d)
variable oxidation state/number;
catalytic properties;
[2]
d sublevel/orbitals split (into two levels by ligands);
electrons absorb light/photons and move to the higher energy orbital;
frequency of light/photons absorbed in the visible region;
[3]
–8–
N13/4/CHEMI/HP2/ENG/TZ0/XX/M
SECTION B
5.
(a)
(b)
(c)
(1) N (NO 2 )3 (g)  2 CH 3OH (l)  2 N 2 (g)  2 CO 2 (g)  4 H 2O (l) ;
products from the reaction are non-toxic / normal components of the atmosphere /
nitrogen is a product rather than oxides of nitrogen;
Accept “no chlorine produced”.
Do not accept “non-polluting”.
[1]
[1]
bonds broken: (6  305)  (3 158)  1830  474  2304 (kJ mol1 ) ;
bonds made: (2  945)  (3  498)  1890  1494  3384 (kJ mol 1 ) ;
enthalpy change: 2304  3384  1080 (kJ mol1 ) ;
Award [3] for correct final answer.
Award [2 max] for  1080(kJ mol 1) .
[3]
Accept –234 kJ mol–1 which arise from students assuming that 305 kJ mol–1 refers
to the strength of a single N–O bond. Students may then take N=O from the data
book value (587 kJ mol–1).
bonds broken: (3  305)  (3  587)  (3  158)  915  1761  474  3150( kJ mol –1)
bonds made: (2  945)  (3  498)  1890  1494  3384( kJ mol 1)
enthalpy change: 3150  3384  234( kJ mol 1) .
Award [2 max] for correct calculation of the enthalpy change of reaction for the
equation in part (a), which gives –2160 (kJ mol–1).
Award [1] if the final answer is not –2160 but the candidate has correctly
calculated the bonds broken in trinitramide as 2304 (kJ mol–1).
(d)
(e)
(f)
(g)
increase in the number of moles of gas;
gases have a greater entropy/degree of randomness (than liquids or solids);
Award [1 max] for answers stating that positive value indicates an increase in
disorder/randomness.
G  H  T  S ;
700
;
 1080  300 
1000
1290 (kJ mol1 ) ;
Award [3] for correct final answer.
Award [2 max] for incorrect conversions of units.
If no answer to part (c), using H  1000 kJ mol 1 , gives 1020( kJ mol 1) .
[2]
[3]
no change in spontaneity / temp has no effect on spontaneity / spontaneous at all
temperatures;
G negative at all temperatures / exothermic/H negative and involves an
increase in entropy/S positive;
[2]
(N–N bond in) trinitramide is longer/nitrogen (gas) is shorter / 0.145 nm in
trinitramide versus 0.110 nm in nitrogen;
trinitramide has single (N–N) bond and nitrogen (gas) has triple bond;
[2]
–9–
(h)
N13/4/CHEMI/HP2/ENG/TZ0/XX/M
106  108 ;
Accept  109 .
Any two for [2 max].
4 (negative) charge centres/electron pairs/electron domains around central
nitrogen;
central nitrogen has a lone/non-bonding pair;
lone/non-bonding pairs repel more than bonding pairs;
molecule will be (trigonal/triangular) pyramidal;
(negative) charge centres/electron pairs/electron domains will be tetrahedrally
arranged/orientated/ have tetrahedral geometry;
Do not apply ECF.
(i)
polar;
net dipole moment present in molecule / unsymmetrical distribution of charge /
polar bonds do not cancel out / centre of negatively charged oxygen atoms does
not coincide with positively charged nitrogen atom;
Marks may also be awarded for a suitably presented diagram showing net dipole
moment.
Do not accept “unsymmetrical molecule”.
Apply ECF from part (h).
[3 max]
[2]
Vapour pressure / kPa
(j)
101.3
Temperature / C
(smooth) upward sloping curve;
Do not award mark for straight line.
boiling point  100 C ;
o
(k)
boiling point / 100 oC
atm P reduced/lower atm P so vp = atm pressure occurs at a lower temperature;
Mark can be gained by suitable lines on graph.
Do not award mark for “boiling point reduced”.
[2]
[1]
– 10 –
(l)
N13/4/CHEMI/HP2/ENG/TZ0/XX/M
rate at which molecules escape into vapour equal to rate at which they return to
liquid;
(at higher temperature) molecules have greater (kinetic) energy;
(at higher temperature) more/greater proportion of molecules have required escape
energy/speed/velocity / more/greater proportion of molecules are able to
evaporate/break free from surface;
greater pressure required for return rate to equal greater escape rate;
Award [1 max] for correct explanations in terms of applying Le Chatelier to an
endothermic change.
[3 max]
– 11 –
6.
(a)
(b)
N13/4/CHEMI/HP2/ENG/TZ0/XX/M
potential of the half-cell / reduction half-reaction under standard conditions
measured relative to standard hydrogen electrode/SHE;
Allow instead of standard conditions, solute concentration of 1 mol dm–3 or
1 bar/1 atm (pressure) for gases.
(i)
Initial oxidation
number
IV/+4
Final oxidation
number
and
III/+3;
[1]
Oxidized / reduced
reduced;
[2]
+ sign must be present. Do not award mark for incorrect notation 4, 4+, 3,
3+ etc.
Do not award M2 if inconsistent with M1.
(ii)
(c)
increases / makes it stronger;
(more H+ would) drive/shift equilibrium to the right/towards products
(accepting more electrons);
KI (aq) is added to a solution containing Ti3+(aq) ions:
no reaction;
Zn (s) is added to a solution containing TiO2+(aq) and H+(aq) ions:
Zn (s)  2TiO2 (aq)  4H  (aq)  Zn 2 (aq)  2Ti3 (aq)  2H 2 O (l)
correct reactants and products;
balanced equation;
Ignore state symbols.
(d)
[2]
(i)
(ii)
[3]
Fe3 (aq)  e   Fe 2 (aq) ;
Ignore state symbols.
Accept equilibrium arrow.
reduction;
Do not apply ECF.
[2]
(0.77  (0.06)) ()0.83(V) ;
[1]
Do not accept –0.83 V.
(iii) wire and salt bridge both have arrows from B to A;
Accept arrows above or below each provided it is obvious which they
refer to.
Apply ECF from part (i).
[1]
– 12 –
(e)
N13/4/CHEMI/HP2/ENG/TZ0/XX/M
(i)
Na2O
SiO2
SO2
Bonding type
ionic
and
(giant/network)
covalent
and
(molecular)
covalent
;
State
solid
and
solid
and
gas
;
decrease
Accept acidic.
;
Effect on
pH
increase
Accept
basic/
alkaline.
and
no effect
Accept small
decrease.
Accept neutral.
and
[3]
For any parts (properties) where mark not awarded, award [1] for every
three correct responses.
(ii)
(combustion of) coal / diesel;
Accept “burning of fossil fuels”, “industrial processes” or “combustion/car
engines”.
Do not accept “Contact process”.
[1]
(iii)
e-pairs correct;
charges in correct positions;
Accept lines, or pairs of dots or crosses, for electron pairs.
[2]
Accept
(f)
(i)
(ii)
(g)
C is sp hybridized and Si is sp3 hybridized;
C–O bond in CO2 has one σ-bond and one π-bond;
Si–O bond in SiO2 has one σ-bond only;
Award [1 max] for last two marking points for “C–O double bond and Si–O
single bond”.
silicon-oxygen bonds will have a tetrahedral distribution;
xenon-oxygen bonds will have a square planar distribution;
xenon dioxide has two non-bonding/lone pairs of electrons;
Award any of the above marks if clearly indicated in suitable diagrams.
SiCl4 (l)  3H 2O (l)  SiO (OH) 2 (s)  4HCl (aq) ;
Accept balanced equations (such as SiCl4 (l)  2H 2O(l)  SiO2 (s)  4HCl (aq) )
with SiO2 and Si(OH)4 as products.
Ignore state symbols.
[3]
[3]
[1]
– 13 –
7.
(a)
arsenic/As;
Accept bismuth/Bi.
(b)
(i)
(d)
SbF5 accepts an electron pair (from F–) / SbF6– donates an electron pair
(to H2F+);
SbF5 acts as a Lewis acid / SbF6– acts as a Lewis base;
[2]
[2]
(i)
H–F bond stronger than H–Cl bond / H–Cl bond weaker than H–F bond;
[1]
(ii)
H–F can hydrogen bond to water and H–Cl cannot;
[1]
(i)
not a good choice / poor choice;
requires same volume of base / the amount/volume to react/for
neutralization does not depend on the acid strength;
[2]
(ii)
phenolphthalein / phenol red;
pH at equivalence point 7 or above;
Accept pH range for colour change/end-point corresponds to rapid change
in pH.
(iii) sulfuric acid is diprotic/dibasic/liberates two protons/H+;
Accept “reacts with 2 moles of alkali/base”.
(iv) weak;
strong 0.100 mol dm–3 acid has a pH of 1/lower than that observed;
Accept “pH value of 3.7 means that it produces only 10–3.7/2.0×10−4 [H+]
in water”.
(e)
[1]
one HF donates a H+/proton and the other accepts a H+/proton;
HF acts as both a Brønsted–Lowry acid and a Brønsted–Lowry base;
Award [1 max] for correct description of HF acting as a Brønsted–Lowry
acid or base.
(ii)
(c)
N13/4/CHEMI/HP2/ENG/TZ0/XX/M
(i)
(ii)
when volume of alkali is half equivalence volume/volume required for
neutralization;
pKa is equal to the pH;
[2]
[1]
[2]
[2]
[H  ]  103.7  2.00 104 (mol dm 3 ) ;
[H  ][Q  ] (2.00 104 ) 2

;
[HQ]
0.100
 3.98 107 ;
pK a  6.4 ;
Award [4] for correct final answer.
Ka 
[4]
– 14 –
(f)
N13/4/CHEMI/HP2/ENG/TZ0/XX/M
amount NaQ  amount NaOH  0.001(mol) ;
excess HQ  0.004  0.001  0.003(mol) ;
1000
1000
[Q ]  0.001
 0.02(mol dm 3 ) and [HQ]  0.003 
 0.06 (mol dm 3 ) ;
50
50
[HQ]
0.06
[H  ]  K a
 1.8 105
 5.4 105 (mol dm 3 ) ;

[Q ]
0.02
pH  log (5.4 105 )  4.268 ;
Accept other methods of reaching the answer.
Award [3 max] if final answer given without working.
[5]
– 15 –
8.
N13/4/CHEMI/HP2/ENG/TZ0/XX/M
Penalise missing hydrogens once only in Q8.
(a)
water/H2O;
Accept steam.
(concentrated) sulfuric acid/H2SO4 (catalyst);
Accept phosphoric acid/H3PO4.
Award [2] for HBr and NaOH (two-stage process via the halogenoalkane).
(b)
(c)
[2]
not react;
tertiary alcohol (not easily oxidized);
[2]
(i)
rotates the plane (of polarization) of plane polarized light;
Accept answers in which one of the “plane”s is missing.
[1]
(ii)
two isomers that are enantiomers/chiral/non-superimposable mirror images;
Accept “contains an asymmetric/chiral carbon” or “contains a carbon
bonded to four different groups”.
[1]
(iii) polarizes light / polarized light source;
light passed through sample;
analyser / second polarizer detects whether plane of polarization rotated;
[3]
(iv)
;
[1]
Accept C3H7–CH(OH)–CH3, but not CH3–CH2–CH2–CH(OH)–CH3.
(d)
2-methylbutan-2-ol has hydroxyl/OH group;
Do not accept “hydroxide group”.
Allow 2-methylbutan-2-ol is an alcohol.
2-methylbutan-2-ol can form H-bonds (to water) / 2-methylbut-2-ene cannot form
H-bonds (to water);
(e)
[2]
(i)
curly arrow showing Cl– leaving;
representation of tertiary carbocation;
curly arrow going from lone pair/negative charge on O in HO– to C+;
Do not allow arrow originating on H in HO–.
formation of organic product CH3CH2C(CH3)2OH and Cl–/NaCl
(somewhere in mechanism);
Award [3 max] if a candidate gives a fully correct SN2 mechanism.
[4]
– 16 –
(ii)
N13/4/CHEMI/HP2/ENG/TZ0/XX/M
rate = k × [2-chloro-2-methylbutane]/[CH3CH2C(CH3)2Cl]/[halogenoalkane]
/[R–Cl];
s–1;
(iii) hydroxide ion/OH– is a better nucleophile than water / hydroxide ion/OH–
has negative charge;
undergo SN2 hydrolysis / RDS depends on attack of OH-/hydroxide ion
(nucleophile);
Accept other suggestions that are chemically valid.
(f)
(g)
[2]
[1 max]
(i)
chlorine can be 35Cl/Cl–35 or 37Cl/Cl–37;
Accept “chlorine can exist as two isotopes”.
Answer must refer to chlorine rather than isotopes in general.
[1]
(ii)
same rate as (isotopes have) same chemical properties;
Accept different rate if reference is made to molecules having different
speeds/collision rate.
[1]
(i)
[1]
Do not accept condensed formulas such as CH3CH2C(CH3)2CN.
Accept the cyanide group as –CN without showing the triple bond.
(ii)
Formation of Y:
cyanide ion/CN– / potassium cyanide/KCN;
Accept hydrogen cyanide/HCN.
Conversion of Y into Z:
hydrogen/H2;
nickel/Ni / platinum/Pt / palladium/Pd (catalyst);
[3]
M14/4/CHEMI/HPM/ENG/TZ1/XX
22146107
CHEMISTRY
Higher level
Paper 1
Monday 19 May 2014 (afternoon)
1 hour
INSTRUCTIONS TO CANDIDATES
• Do not open this examination paper until instructed to do so.
• Answer all the questions.
• For each question, choose the answer you consider to be the best and indicate your choice on
the answer sheet provided.
• The periodic table is provided for reference on page 2 of this examination paper.
• The maximum mark for this examination paper is [40 marks].
2214-6107
19 pages
© International Baccalaureate Organization 2014
2214-6107
23
V
50.94
87
Fr
(223)
88
Ra
(226)
‡
†
89 ‡
Ac
(227)
90
Th
232.04
58
Ce
140.12
91
Pa
231.04
59
Pr
140.91
73
Ta
180.95
38
Sr
87.62
37
Rb
85.47
22
Ti
47.90
56
57 †
72
55
Ba
La
Cs
Hf
132.91 137.34 138.91 178.49
20
Ca
40.08
19
K
39.10
41
Nb
92.91
39
Y
88.91
12
Mg
24.31
11
Na
22.99
92
U
238.03
60
Nd
144.24
74
W
183.85
42
Mo
95.94
24
Cr
52.00
Relative atomic mass
Element
Atomic number
40
Zr
91.22
21
Sc
44.96
4
Be
9.01
2
3
Li
6.94
1
H
1.01
1
30
Zn
65.37
93
Np
(237)
94
Pu
(242)
95
Am
(243)
96
Cm
(247)
97
Bk
(247)
98
Cf
(251)
61
66
62
63
64
65
Pm
Dy
Sm
Tb
Eu
Gd
146.92 150.35 151.96 157.25 158.92 162.50
75
80
76
77
78
79
Re
Os
Pt
Au
Hg
Ir
186.21 190.21 192.22 195.09 196.97 200.59
48
44
45
46
47
Cd
Ru
Rh
Pd
Ag
101.07 102.91 106.42 107.87 112.40
29
Cu
63.55
43
Tc
98.91
28
Ni
58.71
26
Fe
55.85
25
Mn
54.94
27
Co
58.93
The Periodic Table
50
Sn
118.69
32
Ge
72.59
14
Si
28.09
6
C
12.01
4
99
Es
(254)
100
Fm
(257)
67
68
Ho
Er
164.93 167.26
81
82
Tl
Pb
204.37 207.19
49
In
114.82
31
Ga
69.72
13
Al
26.98
5
B
10.81
3
101
Md
(258)
69
Tm
168.93
83
Bi
208.98
51
Sb
121.75
33
As
74.92
15
P
30.97
7
N
14.01
5
35
Br
79.90
17
Cl
35.45
9
F
19.00
7
85
At
(210)
102
No
(259)
103
Lr
(260)
70
71
Lu
Yb
173.04 174.97
84
Po
(210)
52
53
Te
I
127.60 126.90
34
Se
78.96
16
S
32.06
8
O
16.00
6
86
Rn
(222)
54
Xe
131.30
36
Kr
83.80
18
Ar
39.95
10
Ne
20.18
2
He
4.00
0
–2–
M14/4/CHEMI/HPM/ENG/TZ1/XX
–3–
1.
M14/4/CHEMI/HPM/ENG/TZ1/XX
The structural formula of a dioxin is shown below.
O
O
What is its empirical formula?
2.
3.
A.
C6O
B.
C6H4O
C.
C6H6O
D.
C12H8O2
Under which conditions does CH4 have the same number of molecules as 100 cm3 of O2 at 27 °C and
1.0 × 105 Pa?
Volume / cm3
Temperature / °C
Pressure / 105 Pa
A.
50
54
1.0
B.
50
327
1.0
C.
100
54
2.0
D.
100
327
2.0
100.0 cm3 of a 0.50 mol dm–3 solution of BaCl2 is added to 50.0 cm3 of a 0.10 mol dm–3 solution of
Na2SO4. A precipitate of BaSO4 is formed according to the equation below.
BaCl2 (aq) + Na 2SO 4 (aq) → BaSO 4 (s) + 2NaCl (aq)
What is the amount, in mol, of BaSO4 produced?
A.
0.0050
B.
0.010
C.
0.050
D.
0.10
2214-6107
Turn over
M14/4/CHEMI/HPM/ENG/TZ1/XX
–4–
4.
The diagram represents the emission spectrum of hydrogen. Groups of arrows are labelled W, X and Y.
n =7
n =6
n =5
n =4
n =3
Y
n =2
n =1
X
W
Which statement is correct?
5.
A.
The arrows represent the transition of electrons to different energy levels when heat is supplied.
B.
The arrows of W represent emission in the UV region.
C.
The smallest arrow of X represents a violet line in the emission spectrum.
D.
The arrows of Y represent emission of electromagnetic waves with higher energy than those
represented by X and W.
Which electron configurations do not follow the Hund's rule?
1s
2s
I.
↑ ↓
↑ ↓
↑
↑
II.
↑ ↓
↑ ↓
↑ ↓
↑
III.
↑ ↓
↑ ↓
↑
↓
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
2214-6107
2p
↑
↑
M14/4/CHEMI/HPM/ENG/TZ1/XX
–5–
6.
The horizontal axis of the bar chart represents the elements of period 3 from sodium to chlorine
(excluding silicon). What could the vertical axis represent?
P
S
Cl
Na
Mg
Al
Elements of period 3
7.
A.
Melting point of the element
B.
Electronegativity of the bonded atom
C.
Ionic radius of the most common ion
D.
First ionization energy in the gaseous state
Which statements about reactivity are correct?
I.
Potassium reacts more vigorously than sodium with chlorine.
II.
Lithium reacts more vigorously than potassium with water.
III.
Fluorine reacts more vigorously than bromine with a potassium iodide solution.
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
2214-6107
Turn over
M14/4/CHEMI/HPM/ENG/TZ1/XX
–6–
8.
9.
Which ion is colourless?
A.
[Sc (H2O)6]3+
B.
[Cr (H2O)6]3+
C.
[Fe (H2O)6]3+
D.
[Fe (CN)6]3–
The electronegativities of four elements are given in the table.
Element
W
X
Y
Z
Electronegativity
0.9
1.1
3.4
4.0
Which statement is correct?
10.
A.
W and X form an ionic compound.
B.
W and X form a covalent compound.
C.
Y and Z form an ionic compound.
D.
Y and Z form a covalent compound.
Which combination of length and strength of the carbon‒to‒carbon bonds in C2H2 and C2H4
is correct?
Bond length
Bond strength
A.
C2H2 > C2H4
C2H2 < C2H4
B.
C2H2 > C2H4
C2H2 > C2H4
C.
C2H2 < C2H4
C2H2 < C2H4
D.
C2H2 < C2H4
C2H2 > C2H4
2214-6107
–7–
11.
12.
M14/4/CHEMI/HPM/ENG/TZ1/XX
A solid has a melting point of 1582 °C and does not dissolve in water. It does not conduct electricity
in the molten state. What type of structure does the solid have?
A.
Ionic
B.
Metallic
C.
Giant molecular
D.
Simple molecular
The diagrams below show s and p orbitals in different positions. Which combinations can form
a σ-bond?
I.
II.
III.
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
2214-6107
Turn over
M14/4/CHEMI/HPM/ENG/TZ1/XX
–8–
13.
Which species contain delocalized electrons?
I.
S
O
14.
II.
2–
O
O
O
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
O
C
O
A.
III.
CH3
O
H
O
Which statement is correct for the reaction with this enthalpy level diagram?
H
Products
Reactants
Reaction progress
A.
Heat energy is released during the reaction and the reactants are more stable than the products.
B.
Heat energy is absorbed during the reaction and the reactants are more stable than the products.
C.
Heat energy is released during the reaction and the products are more stable than the reactants.
D.
Heat energy is absorbed during the reaction and the products are more stable than the reactants.
2214-6107
–9–
15.
M14/4/CHEMI/HPM/ENG/TZ1/XX
The enthalpy changes of three reactions are given below.
2HCOOH (l) + O 2 (g) → 2CO 2 (g) + 2H 2 O (l)
∆H =
a
C2 H 5OH (l) + 3O 2 (g) → 2CO 2 (g) + 3H 2 O (l)
∆H =
b
2HCOOC2 H 5 (l) + 7O 2 (g) → 6CO 2 (g) + 6H 2 O (l)
∆H =
c
What is the enthalpy change for the following reaction?
HCOOH (l) + C2 H 5OH (l) → HCOOC2 H 5 (l) + H 2 O (l)
16.
17.
A.
a+b+c
B.
a + 2b − c
C.
1
2
a + b + 12 c
D.
1
2
a + b − 12 c
What is the correct definition of lattice enthalpy?
A.
Enthalpy change when one mole of a solid ionic compound is separated into gaseous ions.
B.
Enthalpy change when one mole of a solid ionic compound is separated into its ions in their
standard state.
C.
Enthalpy change when one mole of a solid ionic compound is formed from gaseous elements.
D.
Enthalpy change when one mole of a compound is formed from the elements in their
standard states.
Which reaction has the greatest increase in entropy?
A.
2CH 3OH (l) + 3O 2 (g) → 2CO 2 (g) + 4H 2 O (l)
B.
N 2 (g) + 3H 2 (g) → 2NH 3 (g)
C.
2HCl (aq) + MgCO3 (s) → MgCl2 (aq) + H 2 O (l) + CO 2 (g)
D.
NH 3 (g) + HCl (g) → NH 4 Cl (s)
2214-6107
Turn over
– 10 –
18.
19.
M14/4/CHEMI/HPM/ENG/TZ1/XX
Which change must be negative when a reaction occurs spontaneously?
A.
∆H
B.
∆G
C.
∆S
D.
∆T
The diagram represents the Maxwell‒Boltzmann energy distribution curve of the reactants for a
chemical reaction with different activation energies, Ea1 and Ea2.
Fraction of
molecules
Ea2
Ea1
Energy
What is the reason why the rate of the reaction with activation energy Ea2 is greater?
A.
More frequent collisions between the particles occur.
B.
More energetic collisions between the particles occur.
C.
A catalyst has been added.
D.
The temperature is higher.
2214-6107
M14/4/CHEMI/HPM/ENG/TZ1/XX
– 11 –
20.
X and Y react according to the equation 2X + Y → Z . The reaction can be described by the
following mechanism:
slow
X + X → X2
fast
X2 + Y → Z
What is the order of the reaction with respect to X and Y?
X
21.
Y
A.
First
Zero
B.
First
First
C.
Second
Zero
D.
Second
First
The rate constant for a reaction is determined at different temperatures. Which diagram represents
the relationship between the rate constant, k , and temperature, T , in K ?
B.
A.
k
k
T
D.
C.
k
k
T
2214-6107
T
T
Turn over
– 12 –
22.
23.
M14/4/CHEMI/HPM/ENG/TZ1/XX
Which statement is correct for a reversible reaction when K c >> 1 ?
A.
The reaction almost goes to completion.
B.
The reaction hardly occurs.
C.
Equilibrium is reached in a very short time.
D.
At equilibrium, the rate of the forward reaction is much higher than the rate of the backward
reaction.
The diagram represents the vapour pressure of two liquids, A and B, as temperature changes. Y is a
point on the curve of liquid A.
A
Vapour
pressure
Y
B
Temperature
Which statement can be made using the graph?
A.
At the conditions of pressure and temperature at point Y, A is in the liquid phase and B in the
gaseous phase.
B.
At the conditions of pressure and temperature at point Y, both A and B are in the gaseous phase.
C.
At the same pressure, A has a higher boiling point than B.
D.
The intermolecular forces between the molecules of B are stronger than between the
molecules of A.
2214-6107
– 13 –
24.
25.
26.
27.
M14/4/CHEMI/HPM/ENG/TZ1/XX
In which reaction does H2O act as a Lewis base but not as a Brønsted–Lowry base.
A.
H 2 O + NH 4 + → H 3O + + NH 3
B.
H 2 O + CaO → Ca 2+ + 2OH −
C.
H 2 O + [Fe (H 2 O)6 ]3+ → Fe[(OH)(H 2 O)5 ]2+ + H 3O +
D.
6H 2 O + [Ni (NH 3 )6 ]2+ → 6NH 3 + [Ni (H 2 O)6 ]2+
A solution of 50 cm3 hydrochloric acid has a pH of 4. What is the final pH if 450 cm3 of water
is added?
A.
3
B.
4
C.
5
D.
6
The pKb of HS– is 7.08. What is its conjugate acid and what is the Ka value of the acid?
Conjugate acid
Ka
A.
H2S
10–6.92
B.
H2S
6.92
C.
S2–
10–6.92
D.
S2–
6.92
Which mixture of solutions can be used to prepare a buffer solution?
A.
50.0 cm3 0.100 mol dm–3 HCl and 100.0 cm3 0.100 mol dm–3 NH3
B.
50.0 cm3 0.100 mol dm–3 HCl and 50.0 cm3 0.100 mol dm–3 NH3
C.
50.0 cm3 0.100 mol dm–3 HCl and 100.0 cm3 0.100 mol dm–3 NH4Cl
D.
50.0 cm3 0.100 mol dm–3 HCl and 50.0 cm3 0.100 mol dm–3 NH4Cl
2214-6107
Turn over
M14/4/CHEMI/HPM/ENG/TZ1/XX
– 14 –
28.
A weak acid is titrated with a strong base. Which statement is true for the titration curve?
C
B
pH
A
Volume of base
29.
A.
A is the equivalence point.
B.
The pH at A equals the pKa of the acid.
C.
The pH at B equals 7.
D.
C is in the buffer region.
Methyl orange is an indicator which changes its colour from red to yellow in a pH range of 3.2 – 4.4.
For which titration would methyl orange be a suitable indicator?
A.
Iodine and sodium thiosulfate solution
B.
Hydrochloric acid and ammonia solution
C.
Ethanoic acid and sodium hydroxide solution
D.
Ethanoic acid and ammonia solution
2214-6107
M14/4/CHEMI/HPM/ENG/TZ1/XX
– 15 –
30.
At which side of the equation are electrons, H+ ions and H2O needed to complete the half-equation?
MnO 4 − (aq) → Mn 2+ (aq)
31.
32.
Electrons
H+ ions
H 2O
A.
reactant side
reactant side
product side
B.
reactant side
product side
reactant side
C.
product side
reactant side
product side
D.
product side
product side
reactant side
What are the correct names for KMnO4 and K2Cr2O7 , using oxidation numbers?
A.
Potassium permanganate and potassium dichromate
B.
Potassium manganate(IV) and potassium chromate(VII)
C.
Potassium permanganate(IV) and potassium dichromate(VII)
D.
Potassium manganate(VII) and potassium dichromate(VI)
What is an industrial use of electrolysis?
A.
The production of graphite
B.
The production of iron
C.
The production of electric energy
D.
Electroplating
2214-6107
Turn over
– 16 –
33.
M14/4/CHEMI/HPM/ENG/TZ1/XX
The overall equation of a voltaic cell is:
Ni (s) + 2Ag + (aq)  Ni 2+ (aq) + 2Ag (s)
EÖ =
1.06 V
The standard electrode potential for Ni 2+ (aq) + 2e −  Ni (s) , is – 0.26 V. What is the standard
electrode potential for the silver half-cell, Ag + (aq) + e −  Ag (s) , in V?
34.
A.
–1.32
B.
– 0.80
C.
+ 0.80
D.
+1.32
What is the IUPAC name for (CH3)2COH(CH2)2CH3?
A.
Hexan-3-ol
B.
2-methylpentan-2-ol
C.
2-methylpentan-3-ol
D.
Dimethylpentan-1-ol
2214-6107
M14/4/CHEMI/HPM/ENG/TZ1/XX
– 17 –
35.
Which type of halogenoalkane is the substance shown below, and which type of nucleophilic reaction
does it undergo with an aqueous sodium hydroxide solution?
H
H
C
H
H
H
H
C
H
C
Cl
C
H
36.
H
Type of halogenoalkane
Type of nucleophilic reaction
A.
primary
SN1
B.
tertiary
SN1
C.
primary
SN2
D.
tertiary
SN2
Which reaction produces only butan-2-ol?
A.
Addition of water to but-2-ene
B.
Addition of water to but-1-ene
C.
Reaction of 2-bromobutane with alcoholic sodium hydroxide
D.
Reaction of 1-bromobutane with alcoholic sodium hydroxide
2214-6107
Turn over
M14/4/CHEMI/HPM/ENG/TZ1/XX
– 18 –
37.
Which functional groups are present in C6H5CONHCH3?
CONHCH3
38.
A.
amide and benzene ring (phenyl)
B.
amine, benzene ring (phenyl) and carbonyl
C.
benzene ring (phenyl) and carbonyl
D.
amine and benzene ring (phenyl)
Which two compounds can form a polyester?
A.
HO
C
HO
C
C.
C
O
H
H
OH
H
H
C
C
C
and
HO
HO
O
H
H
H
OH
H
H
C
C
C
and
HO
O
O
H
H
H
OH
H
H
C
C
H
H
C
O
2214-6107
C
and
O
C
D.
H
C
O
B.
H
OH
C
and
O
HO
H
OH
H
OH
– 19 –
39.
40.
M14/4/CHEMI/HPM/ENG/TZ1/XX
Which statement about isomerism is correct?
A.
But-1-ene and but-2-ene are geometrical isomers.
B.
But-1-ene has two geometrical isomers.
C.
Butan-1-ol and butan-2-ol are optical isomers.
D.
Butan-2-ol has two optical isomers.
A student carries out a titration three times and obtains the following volumes: 3.0 ± 0.1 cm3,
3.2 ± 0.1 cm3 and 3.2 ± 0.1 cm3. What is the average volume?
A.
3.1 ± 0.1 cm3
B.
3.13 ± 0.1 cm3
C.
3.1 ± 0.3 cm3
D.
3.13 ± 0.3 cm3
2214-6107
M14/4/CHEMI/HPM/ENG/TZ1/XX/M
MARKSCHEME
May 2014
CHEMISTRY
Higher Level
Paper 1
2 pages
–2–
M14/4/CHEMI/HPM/ENG/TZ1/XX/M
1.
B
16.
A
31.
D
46.
–
2.
D
17.
C
32.
D
47.
–
3.
A
18.
B
33.
C
48.
–
4.
B
19.
C
34.
B
49.
–
5.
C
20.
C
35.
C
50.
–
6.
C
21.
C
36.
A
51.
–
7.
B
22.
A
37.
A
52.
–
8.
A
23.
D
38.
B
53.
–
9.
D
24.
D
39.
D
54.
–
10.
D
25.
C
40.
A
55.
–
11.
C
26.
A
41.
–
56.
–
12.
C
27.
A
42.
–
57.
–
13.
B
28.
B
43.
–
58.
–
14.
B
29.
B
44.
–
59.
–
15.
D
30.
A
45.
–
60.
–
M14/4/CHEMI/HPM/ENG/TZ2/XX
22146113
CHEMISTRY
Higher level
Paper 1
Monday 19 May 2014 (afternoon)
1 hour
INSTRUCTIONS TO CANDIDATES
• Do not open this examination paper until instructed to do so.
• Answer all the questions.
• For each question, choose the answer you consider to be the best and indicate your choice on
the answer sheet provided.
• The periodic table is provided for reference on page 2 of this examination paper.
• The maximum mark for this examination paper is [40 marks].
2214-6113
18 pages
© International Baccalaureate Organization 2014
2214-6113
12
Mg
24.31
20
Ca
40.08
38
Sr
87.62
11
Na
22.99
19
K
39.10
37
Rb
85.47
39
Y
88.91
21
Sc
44.96
40
Zr
91.22
22
Ti
47.90
41
Nb
92.91
23
V
50.94
42
Mo
95.94
24
Cr
52.00
43
Tc
98.91
25
Mn
54.94
Relative atomic mass
Element
Atomic number
27
Co
58.93
28
Ni
58.71
29
Cu
63.55
30
Zn
65.37
31
Ga
69.72
32
Ge
72.59
14
Si
28.09
6
C
12.01
4
87
Fr
(223)
88
Ra
(226)
94
Pu
(242)
95
Am
(243)
96
Cm
(247)
97
Bk
(247)
98
Cf
(251)
99
Es
(254)
100
Fm
(257)
101
Md
(258)
102
No
(259)
103
Lr
(260)
90
91
92
Th
Pa
U
232.04 231.04 238.03
85
At
(210)
‡
84
Po
(210)
58
59
60
61
62
63
64
65
66
67
68
69
70
71
Ce
Pr
Nd
Pm
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
140.12 140.91 144.24 146.92 150.35 151.96 157.25 158.92 162.50 164.93 167.26 168.93 173.04 174.97
93
Np
(237)
36
Kr
83.80
18
Ar
39.95
17
Cl
35.45
35
Br
79.90
10
Ne
20.18
2
He
4.00
0
9
F
19.00
7
†
89 ‡
Ac
(227)
34
Se
78.96
16
S
32.06
15
P
30.97
33
As
74.92
8
O
16.00
6
7
N
14.01
5
86
Rn
(222)
44
45
46
47
48
49
50
51
52
53
54
Ru
Rh
Pd
Ag
Cd
In
Sn
Sb
Te
I
Xe
101.07 102.91 106.42 107.87 112.40 114.82 118.69 121.75 127.60 126.90 131.30
26
Fe
55.85
13
Al
26.98
5
B
10.81
3
55
56
57 †
72
73
74
75
76
77
78
79
80
81
82
83
Cs
Ba
La
Hf
Ta
W
Re
Os
Ir
Pt
Au
Hg
TI
Pb
Bi
132.91 137.34 138.91 178.49 180.95 183.85 186.21 190.21 192.22 195.09 196.97 200.59 204.37 207.19 208.98
4
Be
9.01
2
3
Li
6.94
1
H
1.01
1
The Periodic Table
–2–
M14/4/CHEMI/HPM/ENG/TZ2/XX
M14/4/CHEMI/HPM/ENG/TZ2/XX
–3–
1.
2.
What is the mass, in g, of one mole of hydrated copper(II) sulfate, CuSO4•5H2O, given the following
relative atomic mass values?
A.
160
B.
178
C.
186
D.
250
Element
Cu
S
H
O
Relative atomic mass
64
32
1
16
An excess of calcium carbonate is added to a solution containing 0.10 mol of HCl (aq).
What mass of calcium carbonate reacts, and what mass of carbon dioxide is formed?
Mass of one mole of CaCO3 = 100 g
Mass of one mole of CO 2 = 44 g
CaCO3 (s) + 2HCl (aq) → CaCl2 (aq) + H 2 O (l) + CO 2 (g)
CaCO3 (s) / g
CO2 (g) / g
A.
10
4.4
B.
10
2.2
C.
5.0
2.2
D.
5.0
4.4
2214-6113
Turn over
–4–
3.
For which compounds is the empirical formula the same as the molecular formula?
I.
Methane
II.
Ethene
III.
Ethanol
4.
5.
M14/4/CHEMI/HPM/ENG/TZ2/XX
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
What is the abbreviated electron configuration of the cobalt(II) ion, Co2+?
A.
[Ar] 3d7
B.
[Ar] 4s2 3d5
C.
[Ar] 4s2 3d7
D.
[Ar] 4s1 3d6
Which statement correctly describes the atomic emission spectrum of hydrogen?
A.
It is a continuous spectrum converging at high frequency.
B.
It is a line spectrum converging at high frequency.
C.
It is a continuous spectrum converging at low frequency.
D.
It is a line spectrum converging at low frequency.
2214-6113
–5–
6.
7.
8.
M14/4/CHEMI/HPM/ENG/TZ2/XX
Which equation represents the second ionization energy of potassium?
A.
K(g) → K 2+ (g) + 2e −
B.
K + (g) → K 2+ (g) + e −
C.
K(s) → K 2+ (g) + 2e −
D.
K + (s) → K 2+ (g) + e −
Which pair of elements shows the greatest difference in electronegativity?
A.
Mg and O
B.
Li and F
C.
K and F
D.
Li and I
Which statements explain why a catalyst is used in the Contact process (shown below)?
SO 2 (g) + 12 O 2 (g)  SO3 (g)
I.
A catalyst lowers the activation energy.
II.
A catalyst moves the position of equilibrium towards the product.
III.
A catalyst allows the same rate to be achieved at a lower temperature.
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
2214-6113
Turn over
M14/4/CHEMI/HPM/ENG/TZ2/XX
–6–
9.
10.
11.
Which properties do typical ionic compounds have?
Melting point
Conductivity of solid
A.
high
good
B.
low
good
C.
high
poor
D.
low
poor
What is the difference between the strength and the length of the carbon-oxygen bond in butanal
and in butan-1-ol?
A.
The bond in butanal is stronger and longer than in butan-1-ol.
B.
The bond in butanal is weaker and shorter than in butan-1-ol.
C.
The bond in butanal is weaker and longer than in butan-1-ol.
D.
The bond in butanal is stronger and shorter than in butan-1-ol.
Which allotropes of carbon show sp2 hybridization?
I.
Diamond
II.
Graphite
C60 fullerene
III.
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
2214-6113
M14/4/CHEMI/HPM/ENG/TZ2/XX
–7–
12.
13.
Which molecule is trigonal bipyramidal in shape?
A.
PCl3
B.
SiCl4
C.
PCl5
D.
SF6
Which diagram represents the bonding in SiO2?
B.
A.
Si
O
Si
O
Si
O
O
Si
Si
O
O
Si
D.
C.
O
2214-6113
Si
O
O
Si
O
Si
O
Si
Si
O
Si
O
Si
O
Si
Si
Turn over
–8–
14.
M14/4/CHEMI/HPM/ENG/TZ2/XX
What is the value of ∆H for the exothermic reaction represented by the diagram below?
Enthalpy
x
y
Reactants
Products
z
Reaction coordinate
15.
A.
y–z
B.
z–y
C.
x–z
D.
z–x
Which combination of enthalpy change and entropy change produces a non-spontaneous reaction at
all temperatures?
∆H
∆S
A.
+
–
B.
+
+
C.
–
–
D.
–
+
2214-6113
–9–
16.
17.
18.
19.
M14/4/CHEMI/HPM/ENG/TZ2/XX
Which equation represents the lattice enthalpy of calcium chloride?
A.
CaCl (s) → Ca + (g) + Cl− (g)
B.
CaCl2 (s) → Ca 2+ (g) + 2Cl− (g)
C.
CaCl2 (g) → Ca 2+ (g) + 2Cl− (g)
D.
CaCl2 (s) → Ca 2+ (aq) + 2Cl− (aq)
In which reaction will the entropy of the system increase significantly?
A.
CaCO3 (s) → CaO (s) + CO 2 (g)
B.
H 2 O (g) → H 2 O (l)
C.
HCl (g) + NH 3 (g) → NH 4 Cl (s)
D.
NaOH (aq) + HCl (aq) → NaCl (aq) + H 2 O (l)
Which equation represents the second electron affinity of oxygen?
O 2 (g) + 2e − → O 2− (g)
A.
1
2
B.
O (g) + 2e − → O 2− (g)
C.
O 2 (g) + 4e − → 2O 2− (g)
D.
O − (g) + e − → O 2− (g)
What is the temperature rise when 2100 J of energy is supplied to 100 g of water? (Specific heat
capacity of water = 4.2 J g −1 K −1 .)
A.
5 °C
B.
278 K
C.
0.2 °C
D.
20 °C
2214-6113
Turn over
– 10 –
20.
21.
M14/4/CHEMI/HPM/ENG/TZ2/XX
Which is not affected by an increase in temperature?
A.
Rate of reaction
B.
Collision frequency
C.
Collision geometry
D.
% of molecules with E ≥ Ea
Which combination shows a second-order rate expression with the correct rate constant units?
k units
Rate expression
A.
rate = k [NH 3 ] [BF3 ]
mol dm–3 s–1
B.
rate = k [N 2 O5 ]
s–1
C.
rate = k [N 2 O5 ]
dm3 mol–1 s–1
D.
rate = k [CH 3COCH 3 ] [H + ] [I 2 ]0
dm3 mol–1 s–1
2214-6113
M14/4/CHEMI/HPM/ENG/TZ2/XX
– 11 –
22.
Which pair of graphs shows a decomposition reaction of X that obeys first-order kinetics?
A.
[X]
Rate
[X]
B.
Time
[X]
Rate
[X]
C.
Time
[X]
Rate
[X]
D.
[X]
Rate
[X]
2214-6113
Time
Time
Turn over
– 12 –
23.
M14/4/CHEMI/HPM/ENG/TZ2/XX
What is the equilibrium constant expression, Kc , for this reaction?
2NO (g) + H 2 (g)  N 2 O (g) + H 2 O (g)
24.
25.
A.
Kc =
[N 2 O] + [H 2 O]
2[NO] + [H 2 ]
B.
Kc =
[NO]2 [H 2 ]
[N 2 O] [H 2 O]
C.
Kc =
[2NO] + [H 2 ]
[N 2 O] + [H 2 O]
D.
Kc =
[N 2 O] [H 2 O]
[NO]2 [H 2 ]
Which combination of properties is correct?
Enthalpy of
vaporization
Boiling point
Intermolecular
forces
Volatility
A.
large
high
strong
low
B.
large
low
weak
high
C.
small
low
weak
low
D.
small
high
weak
low
Which compound reacts with calcium oxide, CaO?
A.
K 2O
B.
Na 2O
C.
SO2
D.
MgO
2214-6113
– 13 –
26.
27.
28.
M14/4/CHEMI/HPM/ENG/TZ2/XX
What is the conjugate base of phenol, C6H5OH?
A.
C6 H 4− — OH
B.
C6 H 5 — OH 2
C.
C6 H 5 — O −
D.
C6 H 6+ — OH
+
Which compounds can be mixed together as aqueous solutions of equal volume and concentration to
form an acidic buffer solution?
A.
Sodium hydrogensulfate and sulfuric acid
B.
Sodium propanoate and propanoic acid
C.
Ammonium chloride and ammonia solution
D.
Sodium chloride and hydrochloric acid
Which statements about an acid–base indicator are correct?
I.
It can be a weak acid.
II.
It is a substance in which the conjugate acid/base pair are different colours.
III.
It can be a weak base.
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
2214-6113
Turn over
M14/4/CHEMI/HPM/ENG/TZ2/XX
– 14 –
29.
What is the expression for the ionic product constant of water, Kw?
K=
Ka × Kb
A.
w
K=
Ka + Kb
B.
w
30.
Ka
Kb
C.
Kw =
D.
K=
Ka − Kb
w
Which graph would be obtained by adding 0.10 mol dm–3 HCl (aq) to 25 cm3 of 0.10 mol dm–3
NaOH (aq)?
B.
A.
pH
7
pH
7
25 cm3
D.
C.
pH
7
pH
25 cm3
2214-6113
25 cm3
7
25 cm3
– 15 –
31.
M14/4/CHEMI/HPM/ENG/TZ2/XX
Which species are the oxidizing and reducing agents in the following reaction?
SO32− (aq) + PbO 2 (s) + H 2 O (l) → SO 4 2− (aq) + Pb (OH) 2 (s)
32.
Oxidizing agent
Reducing agent
A.
PbO2
H 2O
B.
SO32–
PbO2
C.
H2O
SO32–
D.
PbO2
SO32–
Zinc is more reactive than copper. In this voltaic cell, which species is reduced and in which direction
do negative ions flow in the salt bridge?
voltmeter
V
salt bridge
Cu rod
Zn rod
CuSO4 (aq)
ZnSO4 (aq)
Species reduced
Direction of negative ion flow in salt bridge
A.
Cu2+
from copper half-cell to zinc half-cell
B.
Cu2+
from zinc half-cell to copper half-cell
C.
Zn2+
from copper half-cell to zinc half-cell
D.
Zn2+
from zinc half-cell to copper half-cell
2214-6113
Turn over
– 16 –
33.
34.
M14/4/CHEMI/HPM/ENG/TZ2/XX
Which components are used to make the standard hydrogen electrode?
A.
H2 (g), H+ (aq), Pt (s)
B.
H2 (g), H+ (aq), Ni (s)
C.
H2 (g), HO– (aq), Pt (s)
D.
H2 (g), HO– (aq), Ni (s)
What is the cell potential, in V, of the reaction below?
I 2 + 2S2 O32− → 2I − + S4 O6 2−
1
2
S4 O6 2− (aq) + e −  S2 O32− (aq)
I 2 (aq) + 2e −  2I − (aq)
35.
A.
+ 0.63
B.
+ 0.45
C.
– 0.45
D.
– 0.63
E Ö = + 0.09 V
E Ö = + 0.54 V
In organic reaction mechanisms, what does a curly arrow represent?
A.
The movement of a pair of electrons towards a nucleophile
B.
The movement of a pair of electrons towards a positively charged species
C.
The movement of a pair of electrons away from a positively charged species
D.
The movement of a pair of electrons towards a Lewis base
2214-6113
– 17 –
36.
37.
38.
M14/4/CHEMI/HPM/ENG/TZ2/XX
Which properties are features of a homologous series?
I.
Same general formula
II.
Similar chemical properties
III.
Gradation in physical properties
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
What does a polarimeter measure?
A.
Colour of reaction mixture
B.
Polarity of a molecule
C.
Configuration of a molecule as R or S
D.
Rotation of plane-polarized light
Which compound can exist as stereoisomers?
A.
1,2-dichloroethane
B.
1,1-dichloroethene
C.
Butan-2-ol
D.
Propan-2-ol
2214-6113
Turn over
M14/4/CHEMI/HPM/ENG/TZ2/XX
– 18 –
39.
What is the structural formula of the ester formed by reacting propanoic acid with
2-methylbutan-2-ol under appropriate conditions?
A.
B.
CH3
H5C2
C
O
CH3
C.
C
CH3
H5C2
C2H 5
O
D.
CH 3
H3C
40.
C
CH3
O
C
C2H5
C
CH3
O
O
C 2H 5
CH3
H3C
O
C
CH3
Which statement about errors is correct?
A.
A random error is always expressed as a percentage.
B.
A systematic error can be reduced by taking more readings.
C.
A systematic error is always expressed as a percentage.
D.
A random error can be reduced by taking more readings.
2214-6113
C
CH 2
O
C
O
C 2 H5
M14/4/CHEMI/HPM/ENG/TZ2/XX/M
MARKSCHEME
May 2014
CHEMISTRY
Higher Level
Paper 1
2 pages
–2–
M14/4/CHEMI/HPM/ENG/TZ2/XX/M
1.
D
16.
B
31.
D
46.
–
2.
C
17.
A
32.
A
47.
–
3.
B
18.
D
33.
A
48.
–
4.
A
19.
A
34.
B
49.
–
5.
B
20.
C
35.
B
50.
–
6.
B
21.
D
36.
D
51.
–
7.
C
22.
C
37.
D
52.
–
8.
B
23.
D
38.
C
53.
–
9.
C
24.
A
39.
A
54.
–
10.
D
25.
C
40.
D
55.
–
11.
C
26.
C
41.
–
56.
–
12.
C
27.
B
42.
–
57.
–
13.
A
28.
D
43.
–
58.
–
14.
B
29.
A
44.
–
59.
–
15.
A
30.
B
45.
–
60.
–
M14/4/CHEMI/HP2/ENG/TZ1/XX
22146108
CHEMISTRY
HIGHER level
Paper 2
Candidate session number
Examination code
Monday 19 May 2014 (afternoon)
2
2 hours 15 minutes
2
1
4
–
6
1
0
8
INSTRUCTIONS TO CANDIDATES
•
•
•
•
•
•
•
•
Write your session number in the boxes above.
Do not open this examination paper until instructed to do so.
Section A: answer all questions.
Section B:answer two questions.
Write your answers in the boxes provided.
A calculator is required for this paper.
A clean copy of the Chemistry Data Booklet is required for this paper.
The maximum mark for this examination paper is [90 marks].
32 pages
© International Baccalaureate Organization 2014
32EP01
M14/4/CHEMI/HP2/ENG/TZ1/XX
–2–
Section a
Answer all questions. Write your answers in the boxes provided.
1.
(a)
Two chemistry students wished to determine the enthalpy of hydration of anhydrous
magnesium sulfate. They measured the initial and the highest temperature reached when
anhydrous magnesium sulfate, MgSO4(s), was dissolved in water. They presented their
results in the table below.
(i)
mass of anhydrous magnesium sulfate / g
3.01
volume of water / cm3
50.0
initial temperature / °C
17.0
highest temperature / °C
26.7
Calculate the amount, in mol, of anhydrous magnesium sulfate.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Calculate the enthalpy change, ∆H1, for anhydrous magnesium sulfate dissolving in
water, in kJ mol–1. State your answer to the correct number of significant figures.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
32EP02
M14/4/CHEMI/HP2/ENG/TZ1/XX
–3–
(Question 1 continued)
(b)
The students repeated the experiment using 6.16 g of solid hydrated magnesium sulfate,
MgSO4•7H2O (s), and 50.0 cm3 of water. They found the enthalpy change, ∆H2 , to be
+18 kJ mol−1.
The enthalpy of hydration of solid anhydrous magnesium sulfate is difficult to determine
experimentally, but can be determined using the diagram below.
MgSO4•7H2O (s)
ΔH2
water
Mg2+(aq) + SO42–(aq)
ΔH1 water
ΔH
MgSO4(s) + 7H2O (l)
(i)
Determine the enthalpy change, ∆H, in kJ mol–1, for the hydration of solid
anhydrous magnesium sulfate, MgSO4.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
The literature value for the enthalpy of hydration of anhydrous magnesium sulfate
is –103 kJ mol–1. Calculate the percentage difference between the literature
value and the value determined from experimental results, giving your answer to
one decimal place. (If you did not obtain an answer for the experimental value in
(b)(i) then use the value of –100 kJ mol–1, but this is not the correct value.)
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
32EP03
–4–
M14/4/CHEMI/HP2/ENG/TZ1/XX
(Question 1 continued)
(c)
Another group of students experimentally determined an enthalpy of hydration of
–95 kJ mol–1. Outline two reasons which may explain the variation between the
experimental and literature values.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (d)
Magnesium sulfate is one of the products formed when acid rain reacts with dolomitic
limestone. This limestone is a mixture of magnesium carbonate and calcium carbonate.
(i)
State the equation for the reaction of sulfuric acid with magnesium carbonate.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Deduce the Lewis (electron dot) structure of the carbonate ion, giving the shape
and the oxygen-carbon-oxygen bond angle.
[3]
Lewis (electron dot) structure:
Shape:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bond angle:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
32EP04
–5–
M14/4/CHEMI/HP2/ENG/TZ1/XX
(Question 1 continued)
(iii) There are three possible Lewis structures that can be drawn for the carbonate ion,
which lead to a resonance structure. Explain, with reference to the electrons, why
all carbon-oxygen bonds have the same length.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [1]
(iv) Deduce the hybridization of the carbon atom in the carbonate ion.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
32EP05
M14/4/CHEMI/HP2/ENG/TZ1/XX
–6–
2.
Sodium thiosulfate solution, Na2S2O3(aq), and hydrochloric acid, HCl (aq), react to produce
solid sulfur as in the equation below.
S2 O32− (aq) + 2H + (aq) → S(s) + SO 2 (g) + H 2 O (l)
The following results to determine the initial rate were obtained:
Experiment
[S2O32–(aq)] / mol dm–3
[H+(aq)] / mol dm–3
Initial rate / mol dm–3 s–1
1
0.200
2.00
0.036
2
0.200
1.00
0.036
3
0.100
1.00
0.018
(a)
Deduce, with a reason, the order of reaction with respect to each reactant.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
[1]
State the rate expression for this reaction.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (c)
Determine the value of the rate constant, k , and state its units.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
32EP06
–7–
M14/4/CHEMI/HP2/ENG/TZ1/XX
(Question 2 continued)
(d)
[1]
State an equation for a possible rate-determining step for the reaction.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (e)
Suggest how the activation energy, Ea , for this reaction may be determined.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
32EP07
M14/4/CHEMI/HP2/ENG/TZ1/XX
–8–
3.
Magnesium has three stable isotopes, 24Mg, 25Mg and 26Mg. The relative abundance of each
isotope is 78.99 %, 10.00 % and 11.01 %, respectively, and can be determined using a mass
spectrometer.
Q
S
X (g)
to vacuum
pump
amplifier
chart
recorder
(a)
Describe the processes occurring at stage Q and stage S.
[4]
Q:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
Calculate, showing your working, the relative atomic mass, Ar , of magnesium, giving
your answer to two decimal places.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32EP08
[2]
M14/4/CHEMI/HP2/ENG/TZ1/XX
–9–
4.
Buta-1,3-diene can be hydrogenated to produce butane, according to the reaction below.
C4 H 6 (g ) + 2H 2 (g ) → C4 H10 (g )
(a)
[2]
State the conditions necessary for this reaction.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
Determine the standard enthalpy change of reaction, ∆H Ö, in kJ mol–1, at 298 K for the
hydrogenation reaction, using Table 11 of the Data Booklet.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (c)
Calculate the standard free energy change, ∆G Ö , in kJ mol–1, at 298 K for the
hydrogenation reaction, using Table 11 of the Data Booklet.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
32EP09
– 10 –
M14/4/CHEMI/HP2/ENG/TZ1/XX
(Question 4 continued)
(d)
(i)
Determine the standard entropy change of the reaction, ∆S Ö , at 298 K, in
kJ K–1 mol–1, using your answers from (b) and (c).
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Explain why the standard entropy change for the hydrogenation of buta-1,3-diene
has a negative sign.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) Predict whether the hydrogenation reaction becomes more or less spontaneous
as the temperature increases.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv) Determine the temperature, in K, at which the spontaneity changes.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
32EP10
– 11 –
M14/4/CHEMI/HP2/ENG/TZ1/XX
(Question 4 continued)
(v)
Determine the standard entropy, S Ö , for hydrogen in J K–1 mol–1, using Table 11 of
the Data Booklet and your answer for (d)(i).
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
32EP11
M14/4/CHEMI/HP2/ENG/TZ1/XX
– 12 –
Section b
Answer two questions. Write your answers in the boxes provided.
5.
(a)
The oxides and chlorides of period 3 elements exhibit periodicity.
(i)
State the changes in the acid-base nature of the oxides across period 3 (from Na2O
to Cl2O7), including equations for the reactions of Na2O and SO3 with water.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
State whether or not molten aluminium chloride, Al2Cl6 , and molten aluminium
oxide, Al2O3 , conduct electricity. Explain this behaviour in terms of the structure
and bonding of the two compounds.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) State the equation for the reaction of Cl2 with water.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
32EP12
M14/4/CHEMI/HP2/ENG/TZ1/XX
– 13 –
(Question 5 continued)
(b)
Chlorine gas, Cl2 (g), is bubbled through separate solutions of aqueous bromine, Br2 (aq),
and potassium bromide, KBr (aq).
(i)
[2]
Predict any changes that may be observed in each case.
Br2(aq):
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . KBr (aq):
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
[2]
State the half-equations for the reactions that occur.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
32EP13
M14/4/CHEMI/HP2/ENG/TZ1/XX
– 14 –
(Question 5 continued)
(c)
The hydrogen halides do not show perfect periodicity. A bar chart of boiling points
shows that the boiling point of hydrogen fluoride, HF, is much higher than periodic trends
would indicate.
Boiling point / K
HF
HCl
HBr
HI
Hydrogen halide
(i)
Explain why the boiling point of HF is much higher than the boiling points of the
other hydrogen halides.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Explain the trend in the boiling points of HCl, HBr and HI.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
32EP14
M14/4/CHEMI/HP2/ENG/TZ1/XX
– 15 –
(Question 5 continued)
(d)
Transition metals form complex ions which are usually coloured.
(i)
State the full electron configurations of Cr and Cr3+.
[2]
Cr:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cr3+:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Cr3+ ions and water molecules bond together to form the complex ion [Cr (H2O)6]3+.
Describe how the water acts and how it forms the bond, identifying the acid-base
character of the reaction.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) Explain why the [Cr(H2O)6]3+ ion is coloured.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
32EP15
– 16 –
M14/4/CHEMI/HP2/ENG/TZ1/XX
(Question 5 continued)
(iv) Outline, including a relevant equation, whether the [Cr (H2O)6]3+ ion is acidic,
basic or neutral.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (e)
Explain how the number of electrons in the outer main energy level of phosphorus, P,
can be determined using the data of successive ionization energies.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32EP16
[2]
M14/4/CHEMI/HP2/ENG/TZ1/XX
– 17 –
6.
Oxidation and reduction can be defined in terms of electron transfer or oxidation numbers.
(a)
Alcohols with the molecular formula C4H9OH occur as four structural isomers. Three
of the isomers can be oxidized with acidified potassium dichromate solution to form
compounds with the molecular formula C4H8O.
(i)
[1]
Deduce the half-equation for the oxidation of the alcohol C4H9OH.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
[1]
Deduce the overall equation for the redox reaction.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) Two of the isomers with the molecular formula C4H9OH can be oxidized further
to form compounds with the molecular formula C4H8O2. Deduce the structural
formulas of these two isomers.
[2]
(This question continues on the following page)
Turn over
32EP17
– 18 –
M14/4/CHEMI/HP2/ENG/TZ1/XX
(Question 6 continued)
(iv) One isomer cannot be oxidized by acidified potassium dichromate solution.
Deduce its structural formula, state its name and identify it as a primary, secondary
or tertiary alcohol.
(v)
Name:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Alcohol:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . All isomers of the alcohol C4H9OH undergo complete combustion. State an
equation for the complete combustion of C4H9OH.
[3]
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
A reactivity series can be experimentally determined by adding the metals W, X, Y and Z
to solutions of these metal ions. The following reactions were observed:
W 2+ (aq) + X (s) → W (s) + X 2+ (aq)
Y (s) + W 2+ (aq) → Y 2+ (aq) + W (s)
Z2+ (aq) + W (s) → Z (s) + W 2+ (aq)
Y (s) + X 2+ (aq) → Y 2+ (aq) + X (s)
(i)
Deduce the order of reactivity of these four metals, from the least to the
most reactive.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
32EP18
– 19 –
M14/4/CHEMI/HP2/ENG/TZ1/XX
(Question 6 continued)
(ii)
A voltaic cell is made by connecting a half-cell of X in XCl2(aq) to a half-cell
of Z in ZCl2(aq). Deduce the overall equation for the reaction taking place when
the cell is operating.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) The standard electrode potential for Z2+ (aq) + 2e −  Z (s) is +0.20 V. State which
species is oxidized when this half-cell is connected to a standard hydrogen electrode.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [3]
(iv) Describe the standard hydrogen electrode including a fully labelled diagram.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
32EP19
– 20 –
M14/4/CHEMI/HP2/ENG/TZ1/XX
(Question 6 continued)
(c)
A student carries out the electrolysis of aqueous potassium iodide, KI, using inert electrodes.
(i)
State the half-equation for the reaction that occurs at each electrode.
[2]
Positive electrode (anode):
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Negative electrode (cathode):
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Suggest, giving a reason, what would happen if the electrodes were changed to
aluminium.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
32EP20
M14/4/CHEMI/HP2/ENG/TZ1/XX
– 21 –
(Question 6 continued)
(d)
Three electrolytic cells were set up in series (one cell after the other), as shown below.
All of the solutions had a concentration of 1.00 mol dm–3.
Inert
electrode
(i)
Sn
Cu
Cu
Graphite
Graphite
SnSO4(aq)
CuSO4(aq)
CuSO4(aq)
Cell 1
Cell 2
Cell 3
Determine the mass of copper produced at one of the electrodes in cell 2 if the tin
electrode in cell 1 decreased in mass by 0.034 g.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Compare the colour and the pH of the solutions in cells 2 and 3 after the current has
been flowing for one hour.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
32EP21
– 22 –
M14/4/CHEMI/HP2/ENG/TZ1/XX
(Question 6 continued)
(iii) Explain your answer given for part (d) (ii).
Colour:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . pH:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32EP22
[2]
– 23 –
7.
(a)
M14/4/CHEMI/HP2/ENG/TZ1/XX
An equilibrium exists between nitrosyl chloride, NOCl, nitrogen oxide, NO, and
chlorine, Cl2.
2 NOCl (g )  2 NO (g ) + Cl2 (g )
(i)
[1]
Deduce the equilibrium constant expression for this reaction.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Explain the effect on the position of equilibrium and the value of Kc when pressure
is decreased and temperature is kept constant.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) 2.00 mol of NOCl was placed in a 1.00 dm3 container and allowed to reach
equilibrium at 298 K. At equilibrium, 0.200 mol of NO was present. Determine the
equilibrium concentrations of NOCl and Cl2 , and hence calculate the value of Kc at
this temperature.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
32EP23
M14/4/CHEMI/HP2/ENG/TZ1/XX
– 24 –
(Question 7 continued)
(iv) The value of Kc is 1.60 × 10–5 at 318 K. State and explain whether the forward
reaction is exothermic or endothermic.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
20.0 cm3 of hexane, C6H14 , and 20.0 cm3 of pentan-1-ol, C5H11OH , were placed separately
into two closed containers at 298 K and allowed to reach equilibrium.
(i)
Compare the two liquids in terms of their boiling points, enthalpies of vaporization
and vapour pressures.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Explain your answer given for part (b)(i).
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
32EP24
M14/4/CHEMI/HP2/ENG/TZ1/XX
– 25 –
(Question 7 continued)
(c)
Ammonia is a weak base.
(i)
Calculate the pH of a 1.50 mol dm–3 solution of ammonia at 298 K to two decimal
places, using Table 15 of the Data Booklet.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
A buffer solution is made using 25.0 cm3 of 0.500 mol dm–3 hydrochloric acid,
HCl (aq), and 20.0 cm3 of 1.50 mol dm–3 ammonia solution, NH3(aq).
Describe the meaning of the term buffer solution.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
32EP25
M14/4/CHEMI/HP2/ENG/TZ1/XX
– 26 –
(Question 7 continued)
(iii) Determine the pH of the buffer solution at 298 K.
[4]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv) A 1.50 mol dm–3 solution of ammonia is added to 25.0 cm3 of a 0.500 mol dm–3
hydrochloric acid solution in a titration experiment.
Calculate the total volume of the solution at the equivalence point.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
32EP26
– 27 –
M14/4/CHEMI/HP2/ENG/TZ1/XX
(Question 7 continued)
(v)
Calculate the pH of the solution at the equivalence point, using Table 15 of the
Data Booklet.
[4]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (vi) Identify a suitable indicator for this titration, using Table 16 of the Data Booklet.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
32EP27
– 28 –
8.
(a)
M14/4/CHEMI/HP2/ENG/TZ1/XX
Outline how electrical conductivity can be used to distinguish between a
0.200 mol dm–3 solution of ethanoic acid, CH3COOH, and a 0.200 mol dm–3 solution of
hydrochloric acid, HCl.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
25.0 cm3 of 0.200 mol dm–3 ethanoic acid was added to 30.0 cm3 of a 0.150 mol dm–3
sodium hydrogencarbonate solution, NaHCO3(aq).
(i)
State an equation for the reaction of ethanoic acid with a solution of sodium
hydrogencarbonate.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Determine which is the limiting reagent. Show your working.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
32EP28
– 29 –
M14/4/CHEMI/HP2/ENG/TZ1/XX
(Question 8 continued)
[2]
(iii) Calculate the mass, in g, of carbon dioxide gas produced.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (c)
The molar mass of a volatile organic liquid, X, can be determined experimentally
by allowing it to vaporize completely at a controlled temperature and pressure.
0.348 g of X was injected into a gas syringe maintained at a temperature of 90 °C and
a pressure of 1.01× 105 Pa. Once it had reached equilibrium, the gas volume was
measured as 95.0 cm3.
(i)
Determine the amount, in mol, of X in the gas syringe.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Calculate the molar mass of X.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
32EP29
– 30 –
M14/4/CHEMI/HP2/ENG/TZ1/XX
(Question 8 continued)
(d)
Bromoethane, CH3CH2Br, undergoes a substitution reaction to form ethylamine,
CH3CH2NH2.
(i)
Deduce the mechanism for the reaction using equations and curly arrows to
represent the movement of electron pairs.
[3]
(ii)
Ethylamine can be produced in two stages starting with iodomethane. Deduce the
reaction pathway and state any necessary conditions.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) Bromoethane can also be converted to ethene. Identify the type of reaction and
state which reagent(s) and conditions are necessary.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
32EP30
M14/4/CHEMI/HP2/ENG/TZ1/XX
– 31 –
(Question 8 continued)
(e)
Many organic compounds exist as stereoisomers.
(i)
Outline the meaning of the term stereoisomers.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
(iii) Explain why this type of stereoisomerism exists in C2H2Cl2.
[1]
Draw the structures of the two stereoisomers of dichloroethene, C2H2Cl2.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
32EP31
– 32 –
M14/4/CHEMI/HP2/ENG/TZ1/XX
(Question 8 continued)
(iv) Draw the structures of the two stereoisomers of 1-chloro-1-fluoroethane, C2H4FCl,
showing the relationship between them.
[1]
(v)
[2]
Outline how the two isomers of C2H4FCl could be distinguished from each other.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32EP32
M14/4/CHEMI/HP2/ENG/TZ1/XX/M
MARKSCHEME
May 2014
CHEMISTRY
Higher Level
Paper 2
15 pages
–2–
M14/4/CHEMI/HP2/ENG/TZ1/XX/M
It is the property of the International Baccalaureate and must not
be reproduced or distributed to any other person without the
authorization of the IB Assessment Centre.
–3–
M14/4/CHEMI/HP2/ENG/TZ1/XX/M
Subject Details: Chemistry HL Paper 2 Markscheme
Mark Allocation
Candidates are required to answer ALL questions in Section A [40 marks] and TWO questions in
Section B [2 x 25 marks]. Maximum total = [90 marks].
1.
A markscheme often has more marking points than the total allows. This is intentional.
2.
Each marking point has a separate line and the end is shown by means of a semicolon (;).
3.
An alternative answer or wording is indicated in the markscheme by a slash (/). Either wording can
be accepted.
4.
Words in brackets ( ) in the markscheme are not necessary to gain the mark.
5.
Words that are underlined are essential for the mark.
6.
The order of marking points does not have to be as in the markscheme, unless stated otherwise.
7.
If the candidate’s answer has the same “meaning” or can be clearly interpreted as being of
equivalent significance, detail and validity as that in the markscheme then award the mark.
Where this point is considered to be particularly relevant in a question it is emphasized by
OWTTE (or words to that effect).
8.
Remember that many candidates are writing in a second language. Effective communication is more
important than grammatical accuracy.
9.
Occasionally, a part of a question may require an answer that is required for subsequent
marking points. If an error is made in the first marking point then it should be penalized. However,
if the incorrect answer is used correctly in subsequent marking points then follow through marks
should be awarded. When marking, indicate this by adding ECF (error carried forward) on the
script.
10.
Do not penalize candidates for errors in units or significant figures, unless it is specifically referred
to in the markscheme.
11.
If a question specifically asks for the name of a substance, do not award a mark for a correct
formula unless directed otherwise in the markscheme, similarly, if the formula is specifically asked
for, unless directed otherwise in the markscheme do not award a mark for a correct name.
12.
If a question asks for an equation for a reaction, a balanced symbol equation is usually expected, do
not award a mark for a word equation or an unbalanced equation unless directed otherwise in the
markscheme.
13.
Ignore missing or incorrect state symbols in an equation unless directed otherwise in the
markscheme.
–4–
M14/4/CHEMI/HP2/ENG/TZ1/XX/M
SECTION A
1.

 3.01 
n (MgSO 4 )  
  0.0250 (mol);
 120.37 
(a)
(i)

(ii)

energy released  50.0  4.18  9.7  2027 (J) / 2.027 (kJ) ;
H1  81(kJ mol1 ) ;
Award [2] for correct answer.
Award [2] if 53.01 is used giving an answer of –86 (kJ mol–1).
Award [1 max] for +81/81/+86/86 (kJ mol−1).
Award [1 max] for –81000/–86000 if units are stated as J mol−1.
Allow answers to 3 significant figures.
(b)
(i)
H ( H1  H 2 )  99 (kJ mol1 ) 
Award [1] if –86 is used giving an answer of –104 (kJ mol–1).
(ii)
(103  99)
100  3.9 % ;
103
Accept answer of 2.9 % if –100 used but only if a value for (b)(i) is not
present.
Award [1] if –104 is used giving an answer of 1.0% .
Accept correct answers which are not to 1 decimal place.
[1]
[2]
[1]
[1]
(c)
MgSO4 not completely anhydrous / OWTTE;
MgSO4 is impure;
heat loss to the atmosphere/surroundings;
specific heat capacity of solution is taken as that of pure water;
experiment was done once only so it is not scientific;
density of solution is taken to be 1 g cm–3;
mass of 7H 2O ignored in calculation;
uncertainty of thermometer is high so temperature change is unreliable;
literature values are carried out under standard conditions, but this experiment is not;
all solid not dissolved;
[2 max]
(d)
(i)
H 2SO4 (aq)  MgCO3 (s)  MgSO4 (aq)  CO2 (g)  H2O(l) ;
Ignore state symbols.
Do not accept H2CO3.
[1]
–5–
M14/4/CHEMI/HP2/ENG/TZ1/XX/M
(ii)
;
Accept crosses, lines or dots as electron pairs.
Accept any correct resonance structure.
Award [0] if structure is drawn without brackets and charge.
Award [0] if lone pairs not shown on O atoms.
shape: trigonal/triangular planar;
bond angle: 120 ;
Accept answers trigonal/triangular planar and 120 if M1 incorrect, but no
other answers should be given credit.
[3]
(iii) (pi/πelectrons are delocalized/spread over more than two nuclei / charge
spread (equally) over all three oxygens;
[1]
(iv)
sp 2 ;
[1]
–6–
2.
3.
(a)
M14/4/CHEMI/HP2/ENG/TZ1/XX/M
experiments 1 and 2 ( [S2 O32 ] remains constant) change in [H ] does not affect
the rate so zero order with respect to H+(aq) / OWTTE;
experiment 1/2 and 3 ( [H ] has no effect) [S2 O32  ] is halved and rate is also
halved so first order with respect to [S2 O32  ] / OWTTE;
Accept explanation given in mathematical terms.
Award [1 max] if both [S2O32–] is first order, and [H+] is zero order are stated
without reason.
[2]
(b)
rate  k [S2O32 ] ;
[1]
(c)
0.18;
s 1 ;
[2]
(d)
S2 O32  S  SO32 ;
Accept any balanced equation that starts with only one S2O32–.
Equations must be balanced in terms of number of atoms and charge.
(e)
determine rate at a range of temperatures (while keeping concentrations constant);
calculate k for each temperature;
plot graph of ln k against T 1 ;
 Ea
/OWTTE;
gradient is
R
(a)
[3 max]
Q: creates positive ions/cations / electron is knocked off atom / OWTTE;
by bombardment of electrons;
S: ions deflected by an (external) magnetic field;
deflection of ions depend on mass/m/z (and charge) / heavier ions are deflected
less than lighter ions / more highly charged ions are deflected more than less
highly charged ions;
Award [1 max] for simply stating ionization and deflection.
(b)
[1]
( Ar ) 0.7899  24  0.1000  25  0.1101  26 ;
24.32 ;
Award [2] for correct final answer.
Award [1 max] for 24.31 with correct working.
Award [0] for 24.31 (Data Booklet value) if working is incorrect or no
working is shown.
Final answer must be to 2 decimal places to score [2].
[4]
[2]
–7–
4.
heat /warm/ 140  225 C ;
Do not accept high temperature.
(finely divided) catalyst / Zn/Cu/Ni/Pd/Pt;
[2]
(b)
H Ö   H f Ö (products)  H f Ö (reactants)  127  (110  0)    237 (kJ mol1 ) ;
[1]
(c)
G Ö   Gf Ö (products)  Gf Ö (reactants)  16  (152  0)    168(kJ mol1 ) ;
[1]
(d)
(i)
(a)
(ii)

M14/4/CHEMI/HP2/ENG/TZ1/XX/M

 H Ö  G Ö  237  (168)
;
S  

T
298


1
1
 0.232(kJ K mol ) ;
Award [2] for correct final answer.
Award [2] for –232 J K –1 mol –1 (units must be given).
Ö
[2]
3 mol of gaseous reactants and 1 mol of gaseous products / fewer moles of
gas in products;
[1]
(iii) spontaneity decreases (as temperature increases because T S Ö becomes a
larger negative value/ G Ö becomes positive at higher temperatures);
[1]
iv G Ö  H Ö  T S Ö  0 / 237  T (0.232)  0 
T  1020 (K);
Remember to allow ECF from 4(d)(i).
[2]
(v)
S Ö  S Ö (products)  S Ö (reactants) / 232  310  (279  2S Ö (H 2 )) ;
S Ö (H 2 )  12 (310  279  232)  132 J K 1 mol1 ;
Award [2] for correct final answer.
Remember to allow ECF from 4(d)(i).
[2]
–8–
M14/4/CHEMI/HP2/ENG/TZ1/XX/M
SECTION B
5.
(a)
(i)
basic to acidic;
Na 2O(s)  H 2O(l)  2NaOH (aq) ;
SO3 (g)  H2O(l)  H 2SO4 (aq) ;
Ignore state symbols.
(ii)
molten Al2Cl6 does not conduct electricity and molten Al2O3 does;
Al2Cl6 is a covalent molecule and has no free charged particles to conduct
electricity;
Al2O3 is ionic/has ions which are free to move when molten;
(iii) Cl2 (g)  H2O(l)  HCl (aq)  HClO(aq) ;
Ignore state symbols.
Allow  .
(b)
(i)
(ii)
(c)
(d)
[3]
Br2 (aq) : no change;
KBr (aq): colour change / from colourless to red/yellow/orange/brown;
[3]
[1]
[2]
2Br  (aq)  Br2 (aq)  2e ;
Cl2 (g)  2e  2Cl (aq) ;
Ignore state symbols.
Accept e instead of e–.
[2]
(i)
HF has hydrogen bonds (between molecules);
[1]
(ii)
strength of van der Waals’/London/dispersion forces increases;
as mass/size/number of electrons of halogen atom/molecule increases;
[2]
(i)
Cr:
Cr 3 :
(ii)
1s 2 2s 2 2p6 3s 2 3p6 4s1 3d5 / 1s 2 2s 2 2p6 3s 2 3p6 3d5 4s1 ;
1s2 2s2 2p6 3s2 3p6 3d3 ;
H2O is a ligand / has lone (electron) pair;
forms dative (covalent)/coordinate bond / donates a lone (electron) pair ;
ligand is Lewis base / Cr 3 is Lewis acid;
(iii) Cr 3 has partially filled d orbitals;
d orbitals split into two levels / three lower energy and two higher energy
levels;
energy difference is in visible part of spectrum;
electrons absorb visible light / one colour/frequency/wavelength;
electron transitions occur from lower to higher energy level within
d sub-level;
complementary colour/colour not absorbed is seen;
[2]
[3]
[3 max]
–9–
M14/4/CHEMI/HP2/ENG/TZ1/XX/M
(iv) acidic because [Cr (H 2O)6 ]3 (aq)  [Cr (H 2 O)5 (OH)]2 (aq)  H  (aq) ;
Allow answers with further equations.
Accept any other valid equations.
Ignore state symbols.
(e)
6.
(a)
successive ionization energy values increase with removal of each electron;
large increase in ionization energy when sixth electron is removed;
as electron is one energy level/shell closer to the nucleus;
Accept a suitably annotated diagram.
[1]
[2 max]
(i)
C4 H9 OH (l)  C4 H8O (l)  2H  (aq)  2e ;
Ignore state symbols.
[1]
(ii)
3C4 H 9 OH (l)  Cr2O 7 2 (aq)  8H  (aq)  3C4 H8O (l)  2Cr 3 (aq)  7H 2 O (l) ;
Ignore state symbols.
[1]
(iii) CH3CH 2CH 2CH 2OH ;
(CH3 )2CHCH2OH ;
Accept full or condensed structural formulas.
(iv)
(v)
(b)
(i)
(ii)
[2]
(CH3 )3COH ;
2-methylpropan-2-ol;
Allow 2-methyl-2-propanol, methylpropan-2-ol, methyl-2-propanol.
tertiary;
[3]
C4 H9OH  6O2  4CO2  5H 2O / (CH3 )3COH  6O2  4CO2  5H 2O
correct reactants and products;
correct balancing;
[2]
Z < W < X < Y;
Accept Y > X > W > Z.
[1]
X (s)  Z2 (aq)  X 2 (aq)  Z(s) ;
Ignore state symbols.
Accept X(s) + ZCl2(aq)  XCl2(aq) + Z(s).
(iii) H2(g)/hydrogen;
[1]
[1]
– 10 –
M14/4/CHEMI/HP2/ENG/TZ1/XX/M
(iv) diagram showing gas, solution and solid electrode;
For example,
H2 (g) at 100 kPa, 298 K
Pt
1 mol dm–3
H+ (aq)
This diagram scores [3].
1 mol dm 3 H  (aq) and Pt;
Allow 1 mol L–1 or 1 M.
Allow 1 mol dm–3 HCl (aq) or other source of 1 mol dm 3 H  (aq) ions.
100 kPa/105 Pa/1 bar ( H 2 (g) pressure) and 298 K / 25 C ;
Ignore state symbols throughout.
Allow 1.01  105 Pa/1 atm.
(c)
(i)
[3]
Positive electrode (anode):
I  (aq)  12 I 2 (aq)  e  ;
Accept correct equation involving 2 mols of I–.
Negative electrode (cathode):
H 2O (l)  e  12 H 2 (g)  OH  (aq) / H  (aq)  e   12 H 2 (g) /
H 3O  (aq)  e   H 2 O (l)  12 H 2 (g) ;
Award [1 max] if correct equations are given at the wrong electrodes.
Ignore state symbols.
Allow e instead of e–.
Penalize equilibrium sign once only.
Accept correct equation involving 2 mols of H+.
(ii)
aluminium will be oxidized (instead of I– ) at positive electrode (anode);
aluminium is a reactive metal / oxidation of aluminium has a positive E Ö /
aluminium is higher on the reactivity series than I– / OWTTE;
[2]
[2]
– 11 –
(d)
(i)
M14/4/CHEMI/HP2/ENG/TZ1/XX/M
n Sn  n Cu  2.86 104 / 0.000286 (mol) ;
m (Cu)  2.86 104  63.55  0.0182(g) ;
(ii)
blue colour persists in second cell and fades in third cell;
pH does not change in second cell and decreases in third cell;
Award [1 max] if both colour and pH are correctly stated for one only of
either second or third cell.
[2]
[2]
(iii) Colour:
positive Cu electrode (anode) is oxidized to maintain colour in second cell /
Cu (s)  Cu 2 (aq)  2e ;
pH:
in third cell, H+ ions are produced as water is oxidized at positive electrode
(anode) / H 2 O (l)  12 O 2 (g)  2H  (aq)  2e  / solution becomes acidic as
hydroxide ions are oxidized at positive electrode (anode) /
2OH  (aq)  12 O 2 (g)  H 2 O (l)  2e  ;
Ignore state symbols.
[2]
– 12 –
7.
(a)
(i)
(ii)
M14/4/CHEMI/HP2/ENG/TZ1/XX/M
[Cl2 (g)][NO(g)]2
;
[NOCl (g)]2
Ignore state symbols.
( K c )
[1]
equilibrium shifts to right as there are more moles (of gas) on product side;
no change to Kc as it is a constant at fixed temperature / OWTTE;
[2]
(iii) [NOCl (g)]  1.80(mol dm3 ) ;
[Cl 2 (g)]  0.100 (mol dm 3 ) ;
 0.100  (0.200) 2 
 1.23 103 (mol dm 3 ) ;
Kc  
2
(1.80)


Award [3] for correct final answer.
(iv) exothermic as Kc is lower at higher temperature;
(b)
(i)
(ii)
(c)
(i)
(ii)
[3]
[1]
hexane has lower boiling point and enthalpy of vaporization than pentan-1-ol /
OWTTE;
hexane has higher vapour pressure than pentan-1-ol / OWTTE;
[2]
hexane is non-polar / has only van der Waals’/London/dispersion forces /
has weaker intermolecular forces than pentan-1-ol;
pentan-1-ol has hydrogen bonding between molecules;
[2]
[OH  ]  1.50  1.78  105  5.17  103 (mol dm 3 ) ;
pH  (14  pOH  14  2.29 )11.71 ;
Award [2] for correct final answer.
Accept correct answer with more than 2 decimal places.
solution which resists change in pH / changes pH slightly / OWTTE;
when small amounts of acid or base are added;
[2]
[2]
– 13 –
M14/4/CHEMI/HP2/ENG/TZ1/XX/M
 (1.50  0.0200)  (0.500  0.0250) 
  0.389 (mol dm 3 ) ;
(iii) [NH 3 ]  
0.0450


 (0.500  0.0250) 
[NH 4  ]  
  0.278(mol dm 3 ) ;
0.0450


 K [NH ]  1.78 105  0.389
 2.49 105 (mol dm 3 ) ;
[OH  ]   b  3  
0.278
 [NH 4 ] 
pH  14.0  pOH  14.0  4.60   9.40 ;
OR
[NH 4  ]
(12.5 /1000)
 pK b  log
;;
[NH3 ]
(17.5 /1000)
 12.5 
pOH  4.75  log 
  4.75  0.146  4.604 ;
 17.5 
pH  14.0  4.604  9.40 ;
Award [4] for the correct final answer.
pOH  pK b  log
(iv)
(v)
25.0  0.500


 8.33cm3 
 V(NH 3 ) 
1.50


V  V(NH 3 )  V(HCl)  8.33  25.0  33.3cm3 / 0.0333dm3 ;
[4]
[1]
(NH4+ ions are present at equivalence point NH 3  HCl  NH 4   Cl at
equivalence n (NH 4  produced)  n (NH 3 added)  n (HCl) )
0.500  0.0250
[NH 4  ] 
 0.375(mol dm 3 ) ;
0.0333

(NH 4 (aq)  NH 3 (aq)  H  (aq) / NH 4  (aq)  H 2 O (l)  NH3 (aq)  H3O  (aq)
pK a (NH 4  )  14  pK b (NH 3 )  14.00  4.75  9.25)
Ka 
[NH3 (aq)][H  (aq)]
 5.62 1010 ;
[NH 4  (aq)]
[H  (aq)]  5.62  1010  0.375  1.45  105 (mol dm 3 ) ;
pH  4.84 ;
Award [4] for the correct final answer.
(vi) bromocresol green / methyl red;
ECF for answer in 7(c)(v) if pH given is below 7.
[4]
[1]
– 14 –
8.
(a)
M14/4/CHEMI/HP2/ENG/TZ1/XX/M
HCl is a strong acid and CH3COOH is a weak acid so HCl has higher
conductivity / HCl dissociates completely in water and CH3COOH does not, so
HCl has higher conductivity / HCl is a stronger acid (than CH3COOH) so has
higher [H+] and higher conductivity;
(b)
(i)
CH 3COOH (aq)  HCO3 (aq)  CH 3COO  (aq)  H 2O (l)  CO 2 (g) ;
Accept NaHCO3(aq) and CH3COONa (aq) instead of ions.
Ignore state symbols.
(ii)
n (CH3COOH)  0.00500(mol) and n (NaHCO3 )  0.00450(mol) ;
NaHCO3 is limiting;
(iii)
(c)
(i)
(ii)
(d)
n (CO2 )  n (NaHCO3 )  0.00450(mol) ;
m (CO2 )  0.00450  44.01  0.198(g) ;
Award [2] for correct final answer.
T  363K and V  9.50 105 m3 ;
Accept V  9.5  10 2 dm3 if P is used as 101 kPa in calculation.
PV 1.01105  9.50 105
;
n

RT
8.31 363
 3.18 103 (mol) ;
Award [3] for correct final answer.
0.348
m

 109 (g mol1 ) ;
M  
3
 n 3.18 10

[1]
[1]
[2]
[2]
[3]
[1]
(i)
curly arrow going from lone pair on N in NH3 to C;
curly arrow showing Br leaving;
Accept curly arrow going from bond between C and Br to Br on
1-bromoethane or on the transition state.
representation of transition state showing square brackets, two partial bonds
and curly arrow going from NH bond to NC partial bond/curly arrow going
from NH bond to N;
Do not penalize if NH3 and Br are not at 180 to each other.
Do not award M3 if NH3—C bond is represented.
(ii)
react CH3I with CN–/KCN solution to form ethanenitrile;
(reduce nitrile by heating with) H2;
Ni (catalyst);
[3]
[3]
– 15 –
M14/4/CHEMI/HP2/ENG/TZ1/XX/M
(iii) elimination;
NaOH /KOH dissolved in (hot) ethanol/alcohol;
heat /hot / reflux;
(e)
(i)
[3]
compounds with same structural formula but different arrangements of
atoms in space;
[1]
(ii)
;
[1]
(iii) restricted rotation around (C=C) double bond;
(iv)
Cl
Cl
C
CH3
H3C
C
;
H
F
F
The two structures must be clear 3D representations of mirror images.
Tapered (wedge/dash) notation not necessary.
H
(v)
[1]
the two enantiomers rotate the plane of plane-polarized light by equal
amounts, but in opposite directions;
using a polarimeter;
[1]
[2]
M14/4/CHEMI/HP2/ENG/TZ2/XX
22146114
CHEMISTRY
HIGHER level
Paper 2
Candidate session number
Examination code
Monday 19 May 2014 (afternoon)
2
2 hours 15 minutes
2
1
4
–
6
1
1
4
INSTRUCTIONS TO CANDIDATES
•
•
•
•
•
•
•
•
Write your session number in the boxes above.
Do not open this examination paper until instructed to do so.
Section A: answer all questions.
Section B:answer two questions.
Write your answers in the boxes provided.
A calculator is required for this paper.
A clean copy of the Chemistry Data Booklet is required for this paper.
The maximum mark for this examination paper is [90 marks].
33 pages
© International Baccalaureate Organization 2014
36EP01
M14/4/CHEMI/HP2/ENG/TZ2/XX
–2–
Section a
Answer all questions. Write your answers in the boxes provided.
1.
A class studied the equilibrium established when ethanoic acid and ethanol react together
in the presence of a strong acid, using propanone as an inert solvent. The equation is
given below.
CH 3COOH + C2 H 5OH  CH 3COOC2 H 5 + H 2 O
One group made the following initial mixture:
Volume / cm3
Liquid
(a)
Ethanoic acid
5.00 ± 0.05
Ethanol
5.00 ± 0.05
6.00 mol dm–3 aqueous hydrochloric acid
1.00 ± 0.02
Propanone
39.0 ± 0.5
The density of ethanoic acid is 1.05 g cm–3. Determine the amount, in mol, of ethanoic
acid present in the initial mixture.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
36EP02
M14/4/CHEMI/HP2/ENG/TZ2/XX
–3–
(Question 1 continued)
(b)
The concentration of ethanoic acid can be calculated as 1.748 mol dm–3. Determine the
percentage uncertainty of this value. (Neglect any uncertainty in the density and the
molar mass.)
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (c)
After one week, a 5.00 ± 0.05 cm3 sample of the final equilibrium mixture was pipetted
out and titrated with 0.200 mol dm–3 aqueous sodium hydroxide to determine the amount
of ethanoic acid remaining. The following titration results were obtained:
Titration number
(i)
1
2
3
Initial reading / cm3 ± 0.05
1.20
0.60
14.60
Final reading / cm3 ± 0.05
28.80
26.50
40.70
Titre / cm3
27.60
25.90
26.10
Calculate the absolute uncertainty of the titre for Titration 1 (27.60 cm3).
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(This question continues on the following page)
Turn over
36EP03
–4–
M14/4/CHEMI/HP2/ENG/TZ2/XX
(Question 1 continued)
(ii)
Suggest the average volume of alkali, required to neutralize the 5.00 cm3 sample,
that the student should use.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) 3.00 cm3 of the 0.200 mol dm–3 aqueous sodium hydroxide reacted with the
hydrochloric acid present in the 5.00 cm3 sample. Determine the concentration of
ethanoic acid in the final equilibrium mixture.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(iv) Deduce the equilibrium constant expression for the reaction.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(This question continues on the following page)
36EP04
M14/4/CHEMI/HP2/ENG/TZ2/XX
–5–
(Question 1 continued)
(v)
The other concentrations in the equilibrium mixture were calculated as follows:
Compound
Concentration / mol dm–3
C2H5OH
CH3COOC2H5
H 2O
0.884
0.828
1.80
Use these data, along with your answer to part (iii), to determine the value of the
equilibrium constant. (If you did not obtain an answer to part (iii), assume the
concentrations of ethanol and ethanoic acid are equal, although this is not the case.)
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(d)
Outline how you could establish that the system had reached equilibrium at the end of
one week.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (e)
Outline why changing the temperature has only a very small effect on the value of the
equilibrium constant for this equilibrium.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
36EP05
–6–
M14/4/CHEMI/HP2/ENG/TZ2/XX
(Question 1 continued)
(f)
Outline how adding some ethyl ethanoate to the initial mixture would affect the
amount of ethanoic acid converted to product.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (g)
Propanone is used as the solvent because one compound involved in the equilibrium is
insoluble in water. Identify this compound and explain why it is insoluble in water.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (h)
Suggest one other reason why using water as a solvent would make the experiment
less successful.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36EP06
[1]
M14/4/CHEMI/HP2/ENG/TZ2/XX
–7–
2.
63
65
Cu and 29
Cu, in naturally occurring copper.
There are only two isotopes, 29
(a)
The relative atomic mass of copper is 63.55. Calculate the percentage of
naturally occurring element.
63
29
Cu in the
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
State the full electronic configuration of a copper atom.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (c)
Explain why most copper(II) compounds are coloured, whereas most copper(I)
compounds are not.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
36EP07
–8–
M14/4/CHEMI/HP2/ENG/TZ2/XX
(Question 2 continued)
(d)
A chemist considered preparing a copper(I) salt by reacting copper metal with the
corresponding copper(II) salt according to the equation below.
Cu 2+ (aq) + Cu (s) → 2Cu + (aq)
(i)
Using data from Table 14 of the Data Booklet, calculate the cell potential for
this reaction.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Use this result to predict, with a reason, whether this reaction will be spontaneous.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36EP08
[1]
–9–
3.
M14/4/CHEMI/HP2/ENG/TZ2/XX
The reaction between 2-bromopropane and potassium hydroxide can produce two different
organic products, depending on the conditions. State the name of each organic product and
outline the conditions needed to give a high yield of each product.
Name
Conditions
Product 1
Product 2
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
...............................
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
[6]
Turn over
36EP09
M14/4/CHEMI/HP2/ENG/TZ2/XX
– 10 –
4.
Ozone, O3 , in the upper atmosphere prevents harmful UV radiation reaching the surface of
the Earth.
(a)
Draw the Lewis structure for ozone.
[1]
(b)
State the shape of the ozone molecule and estimate the bond angle.
[2]
Shape:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bond angle:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (c)
State the hybridization of the central oxygen atom.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (d)
In terms of σ and π bonds, describe the two oxygen-oxygen bonds in the Lewis structure.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
36EP10
– 11 –
M14/4/CHEMI/HP2/ENG/TZ2/XX
(Question 4 continued)
(e)
The two oxygen-oxygen bonds in ozone are in fact of equal length. Deduce why this is
the case and how the length of these would compare to oxygen-oxygen bond lengths in
hydrogen peroxide, H2O2 , and in the oxygen molecule, O2 .
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
36EP11
M14/4/CHEMI/HP2/ENG/TZ2/XX
– 12 –
Section b
Answer two questions. Write your answers in the boxes provided.
5.
Bleaches in which chlorine is the active ingredient are the most common, although some
environmental groups have concerns about their use.
(a)
(i)
Describe the colour change that occurs when aqueous chlorine is added to aqueous
sodium bromide.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Outline, with the help of a chemical equation, why this reaction occurs.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
In aqueous chlorine the equilibrium below produces chloric(I) acid (hypochlorous acid),
HOCl, the active bleach.
Cl2 (aq) + H 2 O (l)  HOCl (aq) + H + (aq) + Cl− (aq)
(i)
Chloric(I) acid is a weak acid, but hydrochloric acid is a strong acid. Outline how
this is indicated in the equation above.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
36EP12
– 13 –
M14/4/CHEMI/HP2/ENG/TZ2/XX
(Question 5 continued)
(ii)
[1]
State a balanced equation for the reaction of chloric(I) acid with water.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) Outline, in terms of the equilibrium in aqueous chlorine, why it is dangerous to use
an acidic toilet cleaner in combination with this kind of bleach.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv) Suggest why a covalent molecule, such as chloric(I) acid, is readily soluble in water.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
36EP13
– 14 –
M14/4/CHEMI/HP2/ENG/TZ2/XX
(Question 5 continued)
(v)
Partial neutralization of chloric(I) acid creates a buffer solution. Given that
the pKa of chloric(I) acid is 7.53, determine the pH of a solution that has
[HOCl] = 0.100 mol dm −3 and [ClO − ] = 0.0500 mol dm −3.
[4]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (vi) Describe, using HIn to represent the indicator in its acid form, why an indicator
changes colour when excess alkali is added.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
36EP14
M14/4/CHEMI/HP2/ENG/TZ2/XX
– 15 –
(Question 5 continued)
(c)
Aqueous sodium chlorate(I), NaOCl, the most common active ingredient in chlorine
based bleaches, oxidizes coloured materials to colourless products while being reduced
to the chloride ion. It will also oxidize sulfur dioxide to the sulfate ion.
(i)
Deduce a balanced equation for the reaction between the chlorate(I) ion and sulfur
dioxide from the appropriate half-equations.
[4]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
State the initial and final oxidation numbers of both chlorine and sulfur in the
final equation.
Element
Initial oxidation number
[2]
Final oxidation number
Chlorine
Sulfur
(d)
The standard electrode potential for the reduction of the chlorate(V) ion to the chloride
ion is +1.49 V.
(i)
Define the term standard electrode potential.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
36EP15
– 16 –
M14/4/CHEMI/HP2/ENG/TZ2/XX
(Question 5 continued)
(ii)
Referring to Table 14 of the Data Booklet, deduce, giving a reason, whether the
oxidation of the chromium(III) ion to the dichromate(VI) ion by the chlorate(V) ion
is energetically feasible.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36EP16
[2]
– 17 –
6.
M14/4/CHEMI/HP2/ENG/TZ2/XX
A group of students investigated the rate of the reaction between aqueous sodium thiosulfate
and hydrochloric acid according to the equation below.
Na 2S2 O3 (aq) + 2HCl (aq) → 2NaCl (aq) + SO 2 (g) + S(s) + H 2 O(l )
The two reagents were rapidly mixed together in a beaker and placed over a mark on a piece
of paper. The time taken for the precipitate of sulfur to obscure the mark when viewed through
the reaction mixture was recorded.
HCl + Na2S2O3
Mark
Initially they measured out 10.0 cm3 of 0.500 mol dm–3 hydrochloric acid and then added
40.0 cm3 of 0.0200 mol dm–3 aqueous sodium thiosulfate. The mark on the paper was obscured
47 seconds after the solutions were mixed.
(a)
The teacher asked the students to measure the effect of halving the concentration of
sodium thiosulfate on the rate of reaction.
(i)
[1]
State the volumes of the liquids that should be mixed.
Liquid
0.500 mol dm–3 HCl
0.0200 mol dm–3 Na 2S2O3
Water
Volume / cm3
(ii)
State why it is important that the students use a similar beaker for both reactions.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
36EP17
M14/4/CHEMI/HP2/ENG/TZ2/XX
– 18 –
(Question 6 continued)
(iii) If the reaction were first order with respect to the thiosulfate ion, predict the time
it would take for the mark on the paper to be obscured when the concentration of
sodium thiosulfate solution is halved.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
One proposed mechanism for this reaction is:
(i)
S2 O32− (aq) + H + (aq)  HS2 O3− (aq)
Fast
HS2 O3− (aq) + H + (aq) → SO 2 (g) + S(s) + H 2 O (l)
Slow
Deduce the rate expression of this mechanism.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
36EP18
M14/4/CHEMI/HP2/ENG/TZ2/XX
– 19 –
(Question 6 continued)
(ii)
The results of an experiment investigating the effect of the concentration of
hydrochloric acid on the rate, while keeping the concentration of thiosulfate at the
original value, are given in the table below.
[HCl] / mol dm–3
0.020
0.040
0.060
0.080
Time / s
89.1
72.8
62.4
54.2
On the axes provided, draw an appropriate graph to investigate the order of the
reaction with respect to hydrochloric acid.
0.00
0.02
0.04
0.06
[3]
0.08
[HCl] / mol dm–3
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
36EP19
– 20 –
M14/4/CHEMI/HP2/ENG/TZ2/XX
(Question 6 continued)
(iii) Identify two ways in which these data do not support the rate expression deduced
in part (i).
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (c)
(i)
Sketch and label, indicating an approximate activation energy, the
Maxwell–Boltzmann energy distribution curves for two temperatures, T1 and T2
(T2 > T1), at which the rate of reaction would be significantly different.
[3]
(This question continues on the following page)
36EP20
– 21 –
M14/4/CHEMI/HP2/ENG/TZ2/XX
(Question 6 continued)
(ii)
Explain why increasing the temperature of the reaction mixture would
significantly increase the rate of the reaction.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (d)
The teacher asked the students to devise another technique to measure the rate of this
reaction.
(i)
One group suggested recording how long it takes for the pH of the solution to
change by one unit. Calculate the initial pH of the original reaction mixture.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Deduce the percentage of hydrochloric acid that would have to be used up for the
pH to change by one unit.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
36EP21
– 22 –
M14/4/CHEMI/HP2/ENG/TZ2/XX
(Question 6 continued)
(e)
Another group suggested collecting the sulfur dioxide and drawing a graph of the volume
of gas against time.
(i)
Calculate the volume of sulfur dioxide, in cm3, that the original reaction mixture
would produce if it were collected at 1.00 ×105 Pa and 300 K.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Sulfur dioxide, a major cause of acid rain, is quite soluble in water and the
equilibrium shown below is established.
SO 2 (aq) + H 2 O (l)  HSO3− (aq) + H + (aq)
Given that the Ka for this equilibrium is 1.25 ×10−2 mol dm −3, determine the pH of a
2.00 mol dm–3 solution of sulfur dioxide.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) Using Table 15 of the Data Booklet, identify an organic acid that is a stronger acid
than sulfur dioxide.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36EP22
[1]
M14/4/CHEMI/HP2/ENG/TZ2/XX
– 23 –
7.
Alkenes, such as A (shown below), are important intermediates in the petrochemical industry
because they undergo addition reactions to produce a wide variety of products, such as the
conversion shown below.
H 3C
C
H3C
H3C
CH3
H
C
CH3
C
H3C
CH3
C
Br
CH3
AB
(a)
State the reagent required to convert A into B.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
It is also possible to convert B into A. Explain the mechanism of this reaction using
curly arrows to represent the movement of electron pairs.
[4]
(This question continues on the following page)
Turn over
36EP23
M14/4/CHEMI/HP2/ENG/TZ2/XX
– 24 –
(Question 7 continued)
(c)
Another way to make B is the reaction shown below.
H 3C
H
C
H 3C
(i)
CH3
C
H3C
H
+ Br2
H
CH3
C
H3C
CH3
C
Br
+ HBr
CH3
State the conditions required for this reaction to occur.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Outline why it would give a poor yield of the desired product.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (d)
B can be converted into C.
H 3C
H
CH3
C
C
H 3C
OH
CH3
C
(i)
[1]
State the reagent required.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
36EP24
M14/4/CHEMI/HP2/ENG/TZ2/XX
– 25 –
(Question 7 continued)
(ii)
State the rate expression that you would expect for the conversion of B to C.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) Explain why C would not be optically active.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv) State why C is not readily oxidized by acidified potassium dichromate(VI).
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (v)
Deduce the structural formula of an isomer of C that would be optically active and
could also be oxidized to a carboxylic acid by acidified potassium dichromate(VI).
[2]
(This question continues on the following page)
Turn over
36EP25
M14/4/CHEMI/HP2/ENG/TZ2/XX
– 26 –
(Question 7 continued)
(e)
In the gas phase, A reacts with hydrogen to form D:
H3C
C
C
H 3C
H
+ H2
CH3
(i)
C
C
H3C
A
CH3
H3C
CH3
H
CH3
D
State the conditions required for this reaction to occur.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Outline a use for hydrogenation reactions like this in the manufacture of foodstuffs.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) State, with a reason, whether you would expect the entropy change for this reaction
to be positive or negative.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
36EP26
– 27 –
M14/4/CHEMI/HP2/ENG/TZ2/XX
(Question 7 continued)
(iv) Given that the enthalpy change of formation of compounds A and D, in the
gas phase, is – 68 kJ mol–1 and –178 kJ mol–1, respectively, calculate the enthalpy
change for the reaction of A with hydrogen.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (v)
Explain how the spontaneity of this reaction would depend on the temperature at
which it was carried out.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (vi) The standard enthalpy change of combustion of A is – 4000 kJ mol–1. Calculate the
amount of A, in mol, that would have to be burned to raise the temperature of 1 dm3
of water from 20 °C to 100 °C .
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
36EP27
– 28 –
M14/4/CHEMI/HP2/ENG/TZ2/XX
(Question 7 continued)
(vii) Compound D is isomeric with hexane. Predict, giving reasons, how the boiling
points of these compounds would compare.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36EP28
[2]
– 29 –
8.
M14/4/CHEMI/HP2/ENG/TZ2/XX
Magnesium, a reactive metal found in many common minerals, is also an essential nutrient
for both plants and animals.
(a)
Define the term first ionization energy.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
Successive ionization energies of magnesium are given in the table below.
Energy required / kJ mol–1
(i)
First
Second
Third
738
1450
7730
Explain why the second ionization energy is greater than the first ionization energy.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Explain why the third ionization energy is much greater than the second
ionization energy.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
36EP29
M14/4/CHEMI/HP2/ENG/TZ2/XX
– 30 –
(Question 8 continued)
(c)
Although magnesium is usually found as Mg2+ in its compounds, it is possible to use
the Born–Haber cycle to investigate the possibility of Mg+ being able to form stable
compounds.
Use the ionization energy data from part (b), along with the other data provided below,
to determine the enthalpy change of formation of MgCl (s). Assume that, because Mg+
would be similar in size to Na+, MgCl would have a similar lattice enthalpy to NaCl.
Enthalpy of atomization of Mg
Bond enthalpy in Cl2
Electron affinity of Cl
Lattice enthalpy of NaCl
+146 kJ mol–1
+243 kJ mol–1
–349 kJ mol–1
+790 kJ mol–1
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (d)
Consider the lattice enthalpies of MgF2 , MgCl2 and CaCl2 . List these from the most
endothermic to the least endothermic and explain your order.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Most endothermic
Least endothermic
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
36EP30
M14/4/CHEMI/HP2/ENG/TZ2/XX
– 31 –
(Question 8 continued)
(e)
Magnesium hydroxide, Mg (OH)2 , is only sparingly soluble in water and the equilibrium
below exists when excess solid is in contact with a saturated solution.
Mg (OH) 2 (s)  Mg 2+ (aq) + 2OH − (aq)
[2]
Outline how the solubility of magnesium hydroxide will vary with pH.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (f)
Magnesium metal is mainly used as a component in lightweight alloys, particularly in
combination with aluminium and titanium.
(i)
[2]
Describe the bonding present in magnesium metal.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
[1]
Suggest why magnesium is harder than sodium.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
36EP31
– 32 –
M14/4/CHEMI/HP2/ENG/TZ2/XX
(Question 8 continued)
(iii) Outline why alloys are generally less malleable than their component metals.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (g)
Magnesium is usually produced by the electrolysis of molten magnesium chloride.
(i)
Draw a labelled diagram of a suitable apparatus for the electrolysis.
[2]
(This question continues on the following page)
36EP32
– 33 –
M14/4/CHEMI/HP2/ENG/TZ2/XX
(Question 8 continued)
(ii)
State equations for the reactions that take place at the electrodes.
[2]
Negative electrode (cathode) reaction:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Positive electrode (anode) reaction:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) When dilute aqueous magnesium chloride is used as the electrolyte, the reactions
at both electrodes are different. State equations for the reactions that occur in
aqueous solution.
[2]
Negative electrode (cathode) reaction:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Positive electrode (anode) reaction:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv) Outline why magnesium metal is not produced in the electrolysis of aqueous
magnesium chloride.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36EP33
[1]
Please do not write on this page.
Answers written on this page
will not be marked.
36EP34
Please do not write on this page.
Answers written on this page
will not be marked.
36EP35
Please do not write on this page.
Answers written on this page
will not be marked.
36EP36
M14/4/CHEMI/HP2/ENG/TZ2/XX/M
MARKSCHEME
May 2014
CHEMISTRY
Higher Level
Paper 2
16 pages
–2–
M14/4/CHEMI/HP2/ENG/TZ2/XX/M
It is the property of the International Baccalaureate and must not
be reproduced or distributed to any other person without the
authorization of the IB Assessment Centre.
–3–
M14/4/CHEMI/HP2/ENG/TZ2/XX/M
Subject Details: Chemistry HL Paper 2 Markscheme
Mark Allocation
Candidates are required to answer ALL questions in Section A [40 marks] and TWO questions in
Section B [2 x 25 marks]. Maximum total = [90 marks].
1.
A markscheme often has more marking points than the total allows. This is intentional.
2.
Each marking point has a separate line and the end is shown by means of a semicolon (;).
3.
An alternative answer or wording is indicated in the markscheme by a slash (/). Either wording can
be accepted.
4.
Words in brackets ( ) in the markscheme are not necessary to gain the mark.
5.
Words that are underlined are essential for the mark.
6.
The order of marking points does not have to be as in the markscheme, unless stated otherwise.
7.
If the candidate’s answer has the same “meaning” or can be clearly interpreted as being of
equivalent significance, detail and validity as that in the markscheme then award the mark.
Where this point is considered to be particularly relevant in a question it is emphasized by
OWTTE (or words to that effect).
8.
Remember that many candidates are writing in a second language. Effective communication is more
important than grammatical accuracy.
9.
Occasionally, a part of a question may require an answer that is required for subsequent
marking points. If an error is made in the first marking point then it should be penalized. However,
if the incorrect answer is used correctly in subsequent marking points then follow through marks
should be awarded. When marking, indicate this by adding ECF (error carried forward) on the
script.
10.
Do not penalize candidates for errors in units or significant figures, unless it is specifically referred
to in the markscheme.
11.
If a question specifically asks for the name of a substance, do not award a mark for a correct
formula unless directed otherwise in the markscheme, similarly, if the formula is specifically asked
for, unless directed otherwise in the markscheme do not award a mark for a correct name.
12.
If a question asks for an equation for a reaction, a balanced symbol equation is usually expected, do
not award a mark for a word equation or an unbalanced equation unless directed otherwise in the
markscheme.
13.
Ignore missing or incorrect state symbols in an equation unless directed otherwise in the
markscheme.
–4–
M14/4/CHEMI/HP2/ENG/TZ2/XX/M
SECTION A
1.
(a)


M(CH 3COOH)  (4 1.01)  (2 12.01)  (2 16.00)  60.06(g mol 1 ) ;
–1
Accept 60 (g mol ).
mass (CH 3COOH) ( 5.00  1.05)  5.25(g) ;
5.25
 0.0874 (mol) ;
60.06
Award [3] for correct final answer.
Accept 0.0875 (comes from using Mr = 60 g mol–1).
(b)
percentage uncertainty in volume of ethanoic acid  100 
[3]
0.05
 1% ;
5.00
0.62
 1.24 % ;
50
total percentage uncertainty  1  1.24  2.24% ;
Accept rounding down to 2.2/2%.
percentage uncertainty in total volume  100 
(c)
(i)
 0.1/ 0.10(cm3 ) ;
Do not accept without .
[1]
(ii)
26.00 (cm3 ) ;
[1]
(iii)
26.00  3.00  23.00 (cm3 ) ;
If other methods used, award M1 for calculating amount of NaOH reacting
with CH3COOH.
23.00
 0.920 (mol dm 3 ) ;
5.00
Award [2] for correct final answer.
If (ii) given as mean titre (26.5 cm3) then ECF answer comes to 0.94 (mol dm–3).
0.200 
(iv)
(v)
(d)
[3]
[CH3COOC2 H5 ][H 2O]
;
[C2 H5OH][CH3COOH]
Do not penalize minor errors in formulas.
[ester ][ water ]
.
Accept ( K c )
[ethanol / alcohol ][(ethanoic) acid ]
( K c )
0.828  1.80
 1.83 ;
0.884  0.920
If assumed [ CH 3COOH ]  0.884 mol dm 3 , answer is 1.91 – allow this even
if an answer was obtained for (iii).
If (ii) given as mean titre (26.5 cm3) then ECF answer comes to 1.79.
( K c )
repeat the titration a day/week later (and result should be the same) / OWTTE;
Accept “concentrations/physical properties/macroscopic properties of the system
do not change”.
[2]
[1]
[1]
[1]
–5–
(e)
enthalpy change/∆H for the reaction is (very) small / OWTTE;
[1]
(f)
decreases (the amount of ethanoic acid converted);
Accept “increases amount of ethanoic acid present at equilibrium” / OWTTE.
(adding product) shifts position of equilibrium towards reactants/LHS / increases
the rate of the reverse reaction / OWTTE;
[2]
(g)
(h)
2.
M14/4/CHEMI/HP2/ENG/TZ2/XX/M
ethyl ethanoate/CH3COOC2H5/ester;
forms only weak hydrogen bonds (to water);
Allow “does not hydrogen bond to water” / “hydrocarbon sections too long” /
OWTTE.
M2 can only be given only if M1 correct.
(large excess of) water will shift the position of equilibrium (far to the left) /
OWTTE;
Accept any other chemically sound response, such as “dissociation of ethanoic
acid would affect equilibrium”.
[2]
[1]
63x  65(100  x)  63.55 100 ;
(x )72.50(%) ;
Award [2] for correct final answer.
[2]
(b)
1s2 2s2 2p6 3s2 3p6 3d10 4s1 / 1s2 2s2 2p6 3s2 3p6 4s1 3d10;
Do not accept upper case letters or numbers as subscripts.
[1]
(c)
colour is due to movement of electrons (between d orbitals) / OWTTE;
copper(I) has a full d sub-shell(, hence electrons cannot move) / copper(II) has an
incomplete d sub-shell(, hence electrons can move) / OWTTE;
(a)
(d)
(i)
E
Ö
cell
[2]

 0.15  0.52   0.37 (V)
Ö
choosing correct E cell values;
combining in correct way;
Award [2] for correct final answer.
Award [1] for -0.18 (0.34 instead of 0.15) and -0.19 (0.34 instead of 0.52).
(ii)
Ö
not spontaneous because E negative / OWTTE;
[2]
[1]
–6–
3.
Product 1
M14/4/CHEMI/HP2/ENG/TZ2/XX/M
Product 2
propan-2-ol;
propene;
Accept 2-propanol/isopropanol.
Accept prop-1-ene/1-propene.
concentrated alkali;
dilute alkali;
aqueous solution;
alcoholic solution;
lower temperature / warm / gentle heat;
Conditions high temperature / reflux / hot;
[2 max] for conditions to form
[2 max] for conditions to form propan-2-ol.
propene.
Accept room temperature.
[6]
Accept Product 1 and Product 2 reversed.
Do not award marks for conditions if product incorrect.
Name
4.
(a)
[1]
Accept lines, dots or crosses to represent electron pairs.
Formal charges and arrow for dative bond not required.
If Lewis structure incorrect remember to take into account possible ECF on parts (b)–
(d) based on the number of electron domains and bond types in the Lewis diagram in
part (a) and do not award marks for these if they are inconsistent with the structure
given in (a).
(b)
Shape: non-linear / bent / v-shaped / angular;
Bond angle: 117 ;
Accept values from 115 to 119  / just/slightly less than 120 .
[2]
(c)
sp2;
[1]
(d)
one is just one  and one has one  and one ;
Accept “both bonds comprise one  and a shared  “/ OWTTE.
[1]
(e)
delocalization occurs / delocalized -bond / (has two) resonance structures / it is a
resonance hybrid;
length intermediate between H 2 O 2 and O 2 / OWTTE;
[2]
–7–
M14/4/CHEMI/HP2/ENG/TZ2/XX/M
SECTION B
5.
(a)
(i)
from (pale) green/colourless to yellow/orange/brown;
Initial colour must be stated.
Do not accept “clear/transparent” instead of “colourless”.
(ii)
chlorine more reactive/more powerful oxidizing agent (than bromine);
Accept opposite statements for bromine.
Accept “chloride ion a weaker reducing agent” / “bromide ion a stronger
reducing agent”.
Accept “chlorine more electronegative than bromine”.
[1]
Cl2 (aq)  2NaBr (aq)  Br2 (aq)  2NaCl (aq) /
Cl 2 (aq)  2Br  (aq)  Br2 (aq)  2Cl  (aq) ;
Ignore state symbols.
Do not accept with equilibrium sign.
(b)
(i)
(ii)
[2]
chloric(I) acid (shown as) a molecule/molecular, but hydrochloric acid
(shown as being) split into ions / OWTTE;
Accept “chloric(I) acid is partially dissociated and hydrochloric acid is
fully dissociated”.
Reference needed to both acids for mark.
[1]
HOCl (aq)  H  (aq)  ClO  (aq) / HOCl (aq)  H 2 O (l)  H 3O  (aq)  ClO  (aq) ;
Equilibrium sign required for the mark.
Ignore state symbols.
(iii) acid displaces the equilibrium to the left (to form chlorine);
chlorine is toxic/poisonous/harmful/lung irritant;
Accept answers that refer to the (b) (ii) equilibrium.
[1]
[2]
(iv) chloric(I) acid has –OH group / hydrogen attached to a very electronegative
atom;
Accept polar molecule.
can form hydrogen bonds to water;
hydrogen bonding to water increases its solubility;
(as a weak acid it is) in equilibrium with ions;
(v)
[2 max]
K a  10 7.53  2.95  10 8 (mol dm 3 ) ;
[H  ][ClO  ] [H  ](0.05) [H  ]


 2.95  108 (mol dm 3 ) ;
[HOCl]
(0.1)
2

8
8
[H ]  2  2.95  10  5.9  10 (mol dm 3 ) ;
pH   log (5.9 108 )  7.23 ;
Accept other methods of carrying out the calculation.
Award [4] for correct final answer.
Ka 
[4]
–8–
(vi)
(c)
(i)
M14/4/CHEMI/HP2/ENG/TZ2/XX/M
HIn  H   In  ;
Do not accept equation without equilibrium arrow.
(weak acid in which the) acid/HIn and conjugate base/In– have different
colours / OWTTE;
excess alkali shifts the equilibrium to the RHS/towards the conjugate base;
[3]
ClO  (aq)  2H  (aq)  2e   H 2 O (l)  Cl  (aq) ;
SO 4 2  (aq)  4H  (aq)  2e   SO 2 (aq)  2H 2 O (l) ;
Accept SO4 2  (aq)  4H  (aq)  2e   H 2 SO3 (aq)  H 2 O(l) .
For final equation:
ClO (aq)  SO2 (aq)  H2O(l)  SO42 (aq)  2H (aq)  Cl (aq)
Accept ClO  (aq)  H 2 SO3 (aq)  SO4 2  (aq)  2H  (aq)  Cl  (aq) .
correct reactants and products;
balancing and cancelling e–, H+ and H 2 O ;
Apply ECF if incorrect half-equations written.
[4]
Ignore state symbols and absence of equilibrium arrow for all equations and
accept inclusion of Na+ in any equation.
(ii)
Award [2] for all correct, [1] for 2 or 3 correct.
Element
Chlorine
Sulfur
Initial oxidation number Final oxidation number
+I / +1;
–I / –1;
+IV / +4;
+VI / +6;
[2]
Remember to apply ECF from final (c) (i) equation.
Penalise incorrect notation (eg, 4 or 4+ rather than +4) once only, so
award [1] for a fully correct answer in an incorrect format.
(d)
(i)
(ii)
potential (of reduction half-reaction) under standard conditions measured
relative to standard hydrogen electrode/SHE / OWTTE;
Allow “solute concentration of 1 mol dm–3” or “1 bar/1 atm (pressure) for
gases” instead of “standard conditions”.
yes / energetically feasible;
would have a positive Ecell / chlorate(V) ion stronger oxidizing agent than
dichromate(VI) ion / OWTTE;
[1]
[2]
–9–
(a)
(i)
Liquid
0.500 mol dm–3 HCl
0.0200 mol dm–3 Na 2S2O3
Water
10(.0)
20(.0)
20(.0)
Volume / cm3
;
[1]
Accept other volumes in a 1:2:2 ratio.
(ii)
depth of liquid in the beaker must remain constant / OWTTE;
Accept “same thickness of glass” and any other valid point, such as
answers framed around minimizing uncontrolled variables / making it a
“fair test”.
(iii) 94 (s) / 1 min 34 s;
(b)
(i)
[1]
[1]
rate  k [S2 O32 ][H  ]2 / rate  k [Na 2S2 O 3 ][HCl]2 ;
[1]
0.0250
(ii)
0.0200
0.0150
Rate / s–1
6.
M14/4/CHEMI/HP2/ENG/TZ2/XX/M
0.0100
0.0050
0.0000
0.00
0.02
0.04
0.06
0.08
[HCl] / mol dm
–3
correct scale and units on y-axis;
Accept other suitable scales (such as 1/t) and units (such as ms–1).
Axes do not have to show origin/start at zero.
correct calculation of rate in s–1;
[HCl] / mol dm–3
0.02
0.04
0.06
0.08
Time / s
89.1
72.8
62.4
54.2
Rate / s–1
0.0112
0.0137
0.0161
0.0185
If graph correct, assume this has been done on calculator and not written down.
correct plotting of points that the student decides to use and a connecting line;
Award final mark if 3 or more points are correct, irrespective of what is plotted
on y-axis.
If line goes through the correct values at given concentrations of HCl, assume
that points are marked there.
[3]
– 10 –
M14/4/CHEMI/HP2/ENG/TZ2/XX/M
(iii) linear dependence on [HCl] (so not second order in [H+]);
Accept that doubling of concentration does not result in quadrupling of rate /
OWTTE .
does not go through origin;
Remember to allow ECF from (b) (i).
(c)
[2]
(i)
Number of particles
T1
T2
Ea
Kinetic energy
labelled y-axis: number of particles / probability of particles (with that
kinetic energy) and labelled x-axis: (kinetic) energy;
Allow fraction/proportion/amount of particles (with kinetic energy) for
y-axis label.
Allow speed/velocity for x-axis label.
T2 curve broader and with maximum lower and to right of T1 curve;
Do not award this mark if both curves not asymmetric.
Curves must pass through the origin and be asymptotic to x axis.
Do not award this mark if curves not labelled.
Ea marked on graph;
(ii)
[3]
kinetic energy of molecules increases;
This may be answered implicitly in the final marking point.
frequency of collision/number of collisions per unit time increases;
Do not accept “number of collisions increases”.
greater proportion of molecules have energy greater than/equal to activation
energy / rate related to temperature by the Arrhenius equation;
Award [1 max] for statements such as “there will be more successful
collisions” if neither of last two marking points awarded.
(d)
(i)
(ii)
[H  ]  0.5 
[3]
10
 0.1(mol dm 3 ) ;
50
pH (   log[H ]   log (0.10))  1 ;
[2]
90 %;
[1]
– 11 –
(e)
(i)
M14/4/CHEMI/HP2/ENG/TZ2/XX/M
mol Na 2S2 O3  mol SO 2  0.0400  0.0200  0.000800 ;
n  R  T 0.000800  8.31 300
;
V
/
P
105
(1.99  105 m3 )  19.9 (cm 3 ) ;
Note that two errors involving a factor of 1000 can also produce the correct
answer. If this is the case award [1] not [3].
Accept 20.0 cm3 if R =8.314 is used.
Award [2] for 17.9 cm3 or 19.2 cm3 (result from using molar volume
at standard temperature and pressure or at room temperature and
pressure).
OR
mol Na 2S2 O3  mol SO 2  0.0400  0.0200  0.000800 ;
1.00 105  300
V  0.00080  2.24 10  

;
5 
 1.0110  273
(1.95105 m3 ) 19.5(cm3 );
Note that two errors involving a factor of 1000 can also produce the correct
answer. If this is the case award [1] not [3].
Deduct [1] for answers based on amount of HCl, so correct calculation
would score [2 max].
2
(ii)
Ka 
[3]
[H  ][HSO3 ]
x2
x2


 1.25  102 (mol dm 3 ) ;
[H 2SO3 ]
2 x 2
[H  ]  2.50  10 2  0.158 (mol dm 3 ) ;
pH   log (0.158)  0.80 ;
Award [3] for correct final answer.
(iii) dichloroethanoic acid / trichloroethanoic acid / 2,4,6-trinitrophenol;
[3]
[1]
7.
(a)
– 12 –
M14/4/CHEMI/HP2/ENG/TZ2/XX/M
hydrogen bromide / hydrobromic acid / HBr;
[1]
(b)
curly arrow going from lone pair/negative charge on O in HO– to H on β-C;
Do not allow curly arrow originating on H in HO–.
Accept mechanism with an alkoxide ion rather than HO– acting as the base.
curly arrow going from CH bond to form C=C bond;
curly arrow showing Br leaving;
formation of organic product and H2O and Br–;
OR
H3C
H
C
H3C
H3C
CH3
C
H
Br
C
H3C
CH3
CH3
C
+
Br
CH3
HO
H3C
CH3
C
H3C
C
+
H2O
CH3
curly arrow showing Br leaving;
representation of tertiary carbocation;
curly arrow going from lone pair on O in HO– to H on C adjacent to C+ and curly
arrow going from CH bond to form C=C bond;
formation of organic product and H2O and Br–;
Deduct [1] if student gives mechanism for the forward reaction instead of the
reverse reaction, so it could score [3 max].
(c)
(d)
(i)
ultraviolet light/sunlight;
Accept “very high temperature”.
(ii)
random/further/multiple substitution (so low probability of desired product)
/ would give a mixture of many different products / OWTTE;
(i)
(aqueous) sodium hydroxide/NaOH / potassium hydroxide/KOH;
Accept hydroxide ion/OH–.
[4]
[1]
[1]
[1]
– 13 –
(ii)
M14/4/CHEMI/HP2/ENG/TZ2/XX/M
rate  k [B] / rate  k [C6 H13 Br] ;
(iii) optical activity requires a chiral/asymmetric centre / OWTTE;
there are no C–atoms that have 4 different groups bonded to them /
mirror image identical to original molecule / OWTTE;
(iv) (it is a) tertiary/3o alcohol / carbon of C–OH is not bonded to a hydrogen;
Accept “it is not a primary or secondary alcohol”.
[1]
[2]
[1]
(v)
Accept abbreviated formulas involving C2H5– and C3H7– .
primary alcohol with formula C6H13OH;
optically active compound with formula C6H13OH;
Penalise minor errors in structures (such as missing H-atoms) once only.
(e)
[2]
(i)
Ni/Pt/Pd catalyst;
[1]
(ii)
conversion of vegetable oil to margarine;
Accept “manufacture of margarine” / “saturation of vegetable oils” /
OWTTE.
[1]
(iii) negative and decrease in number of molecules/particles/moles in the gas phase;
(iv)
H   H f (products)   H f (reactants) / 178  (68) ;
110 (kJ mol1 ) ;
Award [2] for correct final answer.
Award [1] for 110(kJ mol 1 ) .
(v)
[1]
reaction is exothermic/H is negative and involves a decrease in entropy/S
is negative;
reaction will be spontaneous/G negative at low temperatures / nonspontaneous/G positive at high temperatures;
Accept correct explanations using G  H  T S .
Remember to apply ECF from (e) (iii) and (iv) – award both these marks in
accordance with what the candidate has written there.
[2]
[2]
– 14 –
M14/4/CHEMI/HP2/ENG/TZ2/XX/M
(vi) energy required to heat water   m  s  T  1 4.18  (100  20)   334.4(kJ) ;
Ignore sign of energy change.
334.4
 0.0836 (mol) ;
4000
Award [2] for correct final answer.
amount required 
[2]
(vii) D lower/hexane higher and van der Waals’/London/dispersion forces
between molecules weaker in D/stronger in hexane;
Accept “intermolecular forces” instead of dispersion forces.
D is more branched / D has a lower surface area / D has a more
spherical shape / does not pack as closely;
Accept opposite statements for hexane.
[2]
– 15 –
8.
(a)
(b)
(c)
M14/4/CHEMI/HP2/ENG/TZ2/XX/M
minimum energy required to remove one electron / energy required to remove most
loosely bound/outermost electron;
from gaseous/isolated atom;
Accept “gaseous state”.
More extensive definitions involving one mole may be given.
[2]
(i)
electrons lost in same orbital/valence shell;
(second) electron/electron (being lost from Mg+ is) closer to the nucleus;
(second) electron/electron (being lost from Mg+) not subject to e-e repulsion
from others in same level;
[2 max]
Apply OWTTE for all marking points.
Do not accept “less electrons to share the charge” or answers employing
this concept.
(ii)
electron in lower energy level / more stable electron shell;
electron closer to nucleus;
less shielding by complete inner shells / increase in effective nuclear charge;
Apply OWTTE for all marking points.
[2 max]
H at (Cl)  12  243(kJ mol 1 ) ;
Correct calculation of atomization enthalpy of Cl.
H f  146  12 243  738  (349)  (790) ;
Correct sign and magnitude of all terms.
 134 (kJ mol 1 ) ;
Award [3] for correct final answer.
Final mark involves correct computation of equation the student has produced.
Award [2] for –12 (bond enthalpy of Cl not halved) or +134 (signs wrong).
Award [1] for +12 (bond enthalpy of Cl not halved and signs wrong).
(d)
(e)
(f)
MgF2 –MgCl2 –CaCl2 ;
F– smaller (ionic radius) than Cl– / Cl– larger (ionic radius) than F–;
Mg2+ smaller (ionic radius) than Ca2+ / Ca2+ larger (ionic radius) than Mg2+;
Accept use of atomic radius rather than ionic radius.
more soluble at low pH / less soluble at high pH;
higher pH / OH– will shift the equilibrium to the left / lower pH / H+ will (react
with OH– and) shift the equilibrium to the right;
(i)
(ii)
lattice/layers/framework of cations/magnesium ions/Mg2+;
surrounded by delocalized electrons / in a sea/flux of delocalized electrons;
Accept “mobile” instead of “delocalized”.
Mg has more delocalized electrons (than Na);
Accept “Mg has more valence electrons than Na” / “Mg is Mg2+ but Na is
only Na+”.
(iii) layers of ions/atoms/particles cannot slide over each other so easily (as
different sized ions/atoms/particles) / OWTTE;
[3]
[3]
[2]
[2]
[1]
[1]
– 16 –
(g)
M14/4/CHEMI/HP2/ENG/TZ2/XX/M
(i)
Negative electrode
/ cathode
Positive electrode
/ anode
Molten magnesium
chloride / electrolyte
Diagram:
two electrodes connected to a power pack/battery and immersed in an
electrolyte;
Do not award mark if salt bridge included in diagram.
Labelling:
anode/positive electrode, cathode/negative electrode, molten magnesium
chloride/MgCl2 (l)/electrolyte correctly labelled;
Check candidates know which end of a battery symbol is which charge.
(ii)
[2]
Negative electrode (cathode): Mg 2 (l)  2e   Mg (s) ;


Positive electrode (anode): 2Cl (l)  Cl2 (g)  2e ;

[2]

Accept Cl (l)  21 Cl2 (g)  e .
Ignore state symbols.
Allow e instead of e–.
If both correct equations are given for the wrong electrodes award [1 max].
(iii) Negative electrode (cathode):
2H 2 O (l)  2e   H 2 (g)  2OH  (aq) / 2H  (aq)  2e   H 2 (g) ;
Accept 4H 2 O (l)  4e   2H 2 (g)  4OH  (aq) / 4H  (aq)  4e   2H 2 (g) /
H 2 O (l)  e   21 H 2 (g)  OH  (aq) / H  (aq)  e   21 H 2 (g) .
Positive electrode (anode):
2H 2 O (l)  O 2 (g)  4H  (aq)  4e  / 4OH  (aq)  O 2 (g)  2H 2 O (l)  4e  ;



[2]

Accept H 2O (l)  O2 (g)  2H (aq)  2e / 2OH (aq)  O2 (g)  H 2O(l)  2e .
State symbols not required.
Allow e instead of e–.
If both correct equations are given for the wrong electrodes award [1 max].
1
2
1
2
(iv) water/hydrogen ions more easily reduced/better oxidizing agents/have a
Ö
more positive E (than magnesium ions);
Accept converse statements for magnesium ions.
Accept “magnesium is very reactive/high in reactivity series” / OWTTE.
[1]
N14/4/CHEMI/HPM/ENG/TZ0/XX
88146101
CHEMISTRY
HIGHER LEVEL
PAPER 1
Tuesday 18 November 2014 (afternoon)
1 hour
INSTRUCTIONS TO CANDIDATES
• Do not open this examination paper until instructed to do so.
• Answer all the questions.
• For each question, choose the answer you consider to be the best and indicate your choice on
the answer sheet provided.
• The periodic table is provided for reference on page 2 of this examination paper.
• The maximum mark for this examination paper is [40 marks].
8814-6101
18 pages
© International Baccalaureate Organization 2014
8814-6101
23
V
50.94
87
Fr
(223)
88
Ra
(226)
‡
†
89 ‡
Ac
(227)
90
Th
232.04
58
Ce
140.12
91
Pa
231.04
59
Pr
140.91
73
Ta
180.95
38
Sr
87.62
37
Rb
85.47
22
Ti
47.90
56
57 †
72
55
Ba
La
Cs
Hf
132.91 137.34 138.91 178.49
20
Ca
40.08
19
K
39.10
41
Nb
92.91
39
Y
88.91
12
Mg
24.31
11
Na
22.99
92
U
238.03
60
Nd
144.24
74
W
183.85
42
Mo
95.94
24
Cr
52.00
Relative atomic mass
Element
Atomic number
40
Zr
91.22
21
Sc
44.96
4
Be
9.01
2
3
Li
6.94
1
H
1.01
1
30
Zn
65.37
93
Np
(237)
94
Pu
(242)
95
Am
(243)
96
Cm
(247)
97
Bk
(247)
98
Cf
(251)
61
66
62
63
64
65
Pm
Dy
Sm
Tb
Eu
Gd
146.92 150.35 151.96 157.25 158.92 162.50
75
80
76
77
78
79
Re
Os
Pt
Au
Hg
Ir
186.21 190.21 192.22 195.09 196.97 200.59
48
44
45
46
47
Cd
Ru
Rh
Pd
Ag
101.07 102.91 106.42 107.87 112.40
29
Cu
63.55
43
Tc
98.91
28
Ni
58.71
26
Fe
55.85
25
Mn
54.94
27
Co
58.93
The Periodic Table
50
Sn
118.69
32
Ge
72.59
14
Si
28.09
6
C
12.01
4
99
Es
(254)
100
Fm
(257)
67
68
Ho
Er
164.93 167.26
81
82
Tl
Pb
204.37 207.19
49
In
114.82
31
Ga
69.72
13
Al
26.98
5
B
10.81
3
101
Md
(258)
69
Tm
168.93
83
Bi
208.98
51
Sb
121.75
33
As
74.92
15
P
30.97
7
N
14.01
5
35
Br
79.90
17
Cl
35.45
9
F
19.00
7
85
At
(210)
102
No
(259)
103
Lr
(260)
70
71
Lu
Yb
173.04 174.97
84
Po
(210)
52
53
Te
I
127.60 126.90
34
Se
78.96
16
S
32.06
8
O
16.00
6
86
Rn
(222)
54
Xe
131.30
36
Kr
83.80
18
Ar
39.95
10
Ne
20.18
2
He
4.00
0
–2–
N14/4/CHEMI/HPM/ENG/TZ0/XX
–3–
1.
2.
N14/4/CHEMI/HPM/ENG/TZ0/XX
0.040 mol of (NH4)2Ni (SO4)2•6H2O is dissolved in water to give 200 cm3 of aqueous solution.
What is the concentration, in mol dm–3, of ammonium ions?
A.
0.00040
B.
0.0080
C.
0.20
D.
0.40
When sodium bromate(V), NaBrO3, is heated, it reacts according to the equation below.
2NaBrO3 (s) → 2NaBr (s) + 3O2 (g)
What amount, in mol, of NaBrO3 produces 2.4 dm3 of oxygen gas, measured at room temperature
and pressure? (Molar volume of gas = 24 dm3 mol–1 at room temperature and pressure.)
3.
A.
0.017
B.
0.067
C.
0.10
D.
0.15
At which temperature, in K, assuming constant pressure, is the volume of a fixed mass of gas at
127 °C doubled?
A.
200 K
B.
254 K
C.
400 K
D.
800 K
8814-6101
Turn over
N14/4/CHEMI/HPM/ENG/TZ0/XX
–4–
4.
Some possible electron transitions in a hydrogen atom are shown below. Which letter represents the
electron transition with the highest energy in the emission spectrum of a hydrogen atom?
n=5
n=4
n=3
A
B
n=2
Energy
C
D
n=1
5.
Successive ionization energies for an element, Z, are shown in the table below.
Electrons removed
1st
2nd
3rd
Ionization energy / kJ mol–1
736
1450
7740
What is the most likely formula for the ion of Z?
A.
Z+
B.
Z2+
C.
Z3+
D.
Z4+
8814-6101
4th
5th
10 500 13 600
–5–
6.
7.
8.
N14/4/CHEMI/HPM/ENG/TZ0/XX
Which statements are correct for the oxides of period 3 going from Na to Cl?
I.
The oxides become increasingly acidic.
II.
The bonding of the oxides changes from ionic to covalent.
III.
All the oxides dissolve readily in water.
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
The elements argon, potassium, and calcium are consecutive in the periodic table. Which gives the
correct order of increasing first ionization energies?
A.
Ar < Ca < K
B.
K < Ar < Ca
C.
Ca < K < Ar
D.
K < Ca < Ar
Cobalt forms the complex [Co(NH3)5Cl]2+. Which statements are correct for this complex?
I.
The cobalt ion acts as a Lewis acid.
II.
The cobalt ion has an oxidation number of +II.
III.
There are 90° bond angles between the cobalt ion and the ligands.
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
8814-6101
Turn over
–6–
9.
10.
11.
12.
N14/4/CHEMI/HPM/ENG/TZ0/XX
Which species contains a dative covalent (coordinate) bond?
A.
HCN
B.
C2H2
C.
CO2
D.
CO
Which sequence has the molecules in order of increasing nitrogen-nitrogen bond length?
A.
N2 < N2H4 < N2H2
B.
N2 < N2H2 < N2H4
C.
N2H4 < N2H2 < N2
D.
N2H2 < N2H4 < N2
Which process involves the breaking of hydrogen bonds?
A.
2HI (g) → H2(g) + I2 (g)
B.
CH4 (g) → C (g) + 4H (g)
C.
H2 (l) → H2 (g)
D.
NH3 (l) → NH3 (g)
What is the correct number of sigma (σ) and pi (π) bonds in prop-2-enenitrile, CH2CHCN?
σ bonds
π bonds
A.
7
2
B.
4
5
C.
6
3
D.
3
3
8814-6101
–7–
13.
14.
N14/4/CHEMI/HPM/ENG/TZ0/XX
Which group of ions and molecules has delocalized electrons in all the species?
A.
CH3COCH3 , C2H5COO– and O3
B.
NO3–, NO2– and CO2
C.
C6H6 , CO32– and graphite
D.
C6H6 , CO32– and C2H2
Consider the following equations.
2Fe (s) + 1 12 O2 (g) → Fe2 O3 (s)
ΔH À = x
CO (g) + 12 O2 (g) → CO2 (g)
ΔH À = y
What is the enthalpy change of the reaction below?
Fe2O3 (s) + 3CO (g) → 3CO2 (g) + 2Fe (s)
A.
3y – x
B.
3y + x
C.
–3 y – x
D.
–3 y + x
8814-6101
Turn over
N14/4/CHEMI/HPM/ENG/TZ0/XX
–8–
15.
Consider the following bond enthalpy data.
Bond
Bond enthalpy / kJ mol–1
H–H
436
Cl–Cl
243
H–Cl
432
What is the enthalpy change, in kJ mol–1, of this reaction?
H2 (g) + Cl2 (g) → 2HCl (g)
16.
A.
+247
B.
–247
C.
–185
D.
+185
Which processes have a negative value for ΔS À?
I.
H2O (l) → H2O (s)
II.
2H2O2 (l) → 2H2O (l) + O2 (g)
III.
2H2 (g) + O2 (g) → 2H2O (g)
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
8814-6101
–9–
17.
N14/4/CHEMI/HPM/ENG/TZ0/XX
The Born–Haber cycle for the formation of magnesium oxide is shown below.
Mg2+ (g) + O2– (g)
Mg2+ (g) + 2e– + O (g)
X
Enthalpy
Y
Mg (g) + O (g)
Mg (g) + 12 O2 (g)
Mg (s) + 12 O2 (g)
Z
MgO (s)
What is a correct description of the steps X, Y and Z in this cycle?
Step X
Step Y
Step Z
A.
2nd ionization energy of Mg enthalpy of formation of MgO
B.
2nd ionization energy of Mg
lattice enthalpy of MgO
enthalpy of formation of MgO
C.
sum of the 1st and 2nd
ionization energies of Mg
lattice enthalpy of MgO
enthalpy of formation of MgO
D.
sum of 1st and 2nd ionization
enthalpy of formation of MgO
energies of Mg
8814-6101
lattice enthalpy of MgO
lattice enthalpy of MgO
Turn over
– 10 –
18.
N14/4/CHEMI/HPM/ENG/TZ0/XX
Consider the values of ΔH À and ΔS À for the reaction of nitrogen with oxygen at 298 K.
N2 (g) + O2 (g) → 2NO (g)
ΔH À = +181 kJ mol–1
ΔS À = +25 J K–1 mol–1
Which statement is correct for this reaction?
19.
A.
ΔG À is positive at all temperatures.
B.
ΔG À is negative at all temperatures.
C.
ΔG À is positive at high temperatures.
D.
ΔG À is positive at low temperatures.
Consider the following reaction between hydrogen peroxide, hydrogen ions and iodide ions.
H2O2 (aq) + 2H+ (aq) + 2I– (aq) → I2 (aq) + 2H2O (l)
Which changes could be used to investigate the rate of this reaction?
I.
Electrical conductivity
Mass of solution
II.
III.
Colour intensity
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
8814-6101
– 11 –
20.
N14/4/CHEMI/HPM/ENG/TZ0/XX
Consider the following reaction between nitrogen monoxide and oxygen.
2NO (g) + O2 (g) → 2NO2 (g)
The reaction occurs in two steps:
Step 1:
NO (g) + NO (g)  N2O2 (g)
fast
Step 2:
N2O2 (g) + O2 (g) → 2NO2 (g)
slow
What is the rate expression for this reaction?
21.
A.
Rate = k [NO]2
B.
Rate = k [NO][O2 ]
C.
Rate = k [NO]2[O2 ]
D.
Rate = k [NO][O2 ]2
What happens to the rate constant, k, and the activation energy, Ea , as the temperature of a chemical
reaction is increased?
Value of k
Value of Ea
A.
increases
increases
B.
unchanged
increases
C.
decreases
unchanged
D.
increases
unchanged
8814-6101
Turn over
– 12 –
22.
23.
Which equilibrium reaction shifts to the product side when the temperature is increased at constant
pressure and to the reactant side when the total pressure is increased at constant temperature?
A.
N2 (g) + 3H2 (g)  2NH3 (g)
ΔH À < 0
B.
N2O4 (g)  2NO2 (g)
ΔH À > 0
C.
H2 (g) + I2 (g)  2HI (g)
ΔH À < 0
D.
PCl3 (g) + Cl2 (g)  PCl5 (g)
ΔH À > 0
A mixture of 2.0 mol of H2 and 2.0 mol of I2 is allowed to reach equilibrium in the gaseous state at a
certain temperature in a 1.0 dm3 flask. At equilibrium, 3.0 mol of HI are present. What is the value
of Kc for this reaction?
H2 (g) + I2 (g)  2HI (g)
24.
N14/4/CHEMI/HPM/ENG/TZ0/XX
A.
Kc =
(3.0)2
(0.5)2
B.
Kc =
3.0
(0.5)2
C.
(3.0)2
Kc =
(2.0)2
D.
Kc =
(0.5)2
(3.0)2
Which definition of a base is correct?
A.
A Lewis base accepts a proton.
B.
A Brønsted–Lowry base accepts an electron pair.
C.
A Brønsted–Lowry base donates an electron pair.
D.
A Lewis base donates an electron pair.
8814-6101
– 13 –
25.
26.
27.
N14/4/CHEMI/HPM/ENG/TZ0/XX
A student adds 0.3 g of magnesium metal to equal volumes of hydrochloric acid and ethanoic acid of
the same concentrations in separate flasks. Which statement is correct?
A.
Hydrochloric acid reacts more rapidly as it has a higher pH than ethanoic acid.
B.
A greater total volume of H2 gas is produced with hydrochloric acid than with ethanoic acid.
C.
The same total volume of H2 gas is produced with both hydrochloric acid and ethanoic acid.
D.
Ethanoic acid reacts more slowly because it has a lower pH than hydrochloric acid.
Which compound will produce an aqueous solution which has a pH greater than 7?
A.
CuSO4
B.
FeCl3
C.
Na2CO3
D.
NH4NO3
Methylamine acts as a weak base when it reacts with water. For a diluted aqueous solution, what is
the Kb expression for this reaction?
A.
[CH3 NH3 + ][OH – ]
Kb =
[CH3 NH2]
B.
Kb =
C.
[CH3 NH3+ ][OH– ]
Kb =
[CH3 NH2 ][H2O ]
D.
Kb =
8814-6101
[CH3 NH2 ][H2O ]
[CH3 NH3+ ][OH– ]
[CH3 NH2 ]
[CH3 NH3+ ][OH– ]
Turn over
– 14 –
28.
N14/4/CHEMI/HPM/ENG/TZ0/XX
A buffer solution is formed by mixing equal volumes of 1.00 mol dm–3 propanoic acid and
0.500 mol dm–3 potassium propanoate.
What is the concentration, in mol dm–3, of [H+(aq)] in this buffer solution? (Ka for propanoic acid is
1.30 × 10–5.)
29.
30.
A.
2.60 × 10–5
B.
1.95 × 10–5
C.
1.30 × 10–5
D.
0.650 × 10–5
The acid–base indicator phenol red, HIn, changes colour from yellow to red over a pH range of
6.6–8.2. Which statement is correct?
A.
In a strongly acidic solution [HIn] < [In–].
B.
The pKa of phenol red is between 6.6 and 8.2.
C.
The In– ions are yellow.
D.
Phenol red would be a suitable indicator for the titration of a strong acid and a weak base.
Which statement is correct for the following reaction?
2ClO3– (aq) + SO2 (aq) + H+ (aq) → 2ClO2 (g) + HSO4– (aq)
A.
ClO3– is the oxidizing agent and it undergoes reduction.
B.
ClO3– is the reducing agent and it undergoes oxidation.
C.
SO2 is the oxidizing agent and it undergoes oxidation.
D.
SO2 is the reducing agent and it undergoes reduction.
8814-6101
– 15 –
31.
Which species are produced at each electrode during the electrolysis of molten lead(II) bromide,
PbBr2(l)?
Negative electrode
(cathode)
32.
N14/4/CHEMI/HPM/ENG/TZ0/XX
Positive electrode
(anode)
A.
Br–(l)
Pb2+(l)
B.
Pb2+(l)
Br–(l)
C.
Br2(g)
Pb (l)
D.
Pb (l)
Br2(g)
Consider the following standard electrode potentials.
Sn2+ (aq) + 2e–  Sn (s)
E À = – 0.14 V
H+ (aq) + e–  12 H2 (g)
E À = 0.00 V
Fe3+ (aq) + e–  Fe2+ (aq)
E À = + 0.77 V
Which species will reduce H+(aq) to H2(g) under standard conditions?
33.
A.
Fe2+(aq)
B.
Sn2+(aq)
C.
Sn (s)
D.
Fe3+(aq)
A number of molten metal chlorides are electrolysed, using the same current for the same length
of time. Which metal will be produced in the greatest amount, in mol?
A.
Mg
B.
Al
C.
K
D.
Ca
8814-6101
Turn over
N14/4/CHEMI/HPM/ENG/TZ0/XX
– 16 –
34.
35.
36.
Which product is formed when bromine water is added to propene, CH3CHCH2?
A.
CH3CBr2CH3
B.
CH2BrCH2CH2Br
C.
CH3CHBrCH2Br
D.
CH3CH2CH2Br
Which equation represents a propagation step in the reaction of methane with bromine?
A.
CH4 → CH3  + H 
B.
CH4 + Br  → CH3  + HBr
C.
CH4 + Br  → CH3Br + H 
D.
CH3  + Br  → CH3Br
Which of these repeating units is present in the polymer poly(propene)?
A.
C.
8814-6101
H
H
C
H
B.
H
H
C
C
C
H
CH3 CH3
CH3 H
D.
H
H
C
C
C
C
H
CH3
H
CH3
– 17 –
37.
38.
N14/4/CHEMI/HPM/ENG/TZ0/XX
Chloroethane, C2H5Cl, reacts with concentrated ammonia, NH3, to form ethanamine, C2H5NH2.
Which statement about the mechanism of this reaction is correct?
A.
The reaction follows an SN1 mechanism.
B.
Homolytic fission of the carbon-chlorine bond occurs in chloroethane.
C.
The reaction is unimolecular.
D.
There is no charge on the transition state.
Which combination of monomers produces a condensation polymer with the repeating unit below?
OC
COOCH2CH2O
n
A.
C6H5COOH and HOCH2CH2OH
B.
C6H5COOH and CH3CH2OH
C.
C6H4(COOH)2 and CH3CH2OH
D.
C6H4(COOH)2 and HOCH2CH2OH
8814-6101
Turn over
– 18 –
39.
40.
N14/4/CHEMI/HPM/ENG/TZ0/XX
Which type(s) of stereoisomerism, if any, is/are present in the molecule CH2=CHCHBrCH3?
A.
Optical only
B.
Geometric only
C.
Optical and geometric
D.
Neither optical nor geometric
In an experiment to determine a specific quantity, a student calculated that her experimental
uncertainty was 0.9 % and her experimental error was 3.5 %. Which statement is correct?
A.
Only random uncertainties are present in this experiment.
B.
Both random uncertainties and systematic errors are present in this experiment.
C.
Repeats of this experiment would reduce the systematic errors.
D.
Repeats of this experiment would reduce both systematic errors and random uncertainties.
8814-6101
N14/4/CHEMI/HPM/ENG/TZ0/XX/M
MARKSCHEME
November 2014
CHEMISTRY
Higher Level
Paper 1
2 pages
–2–
N14/4/CHEMI/HPM/ENG/TZ0/XX/M
1.
D
16.
B
31.
D
46.
–
2.
B
17.
C
32.
C
47.
–
3.
D
18.
D
33.
C
48.
–
4.
B
19.
B
34.
C
49.
–
5.
B
20.
C
35.
B
50.
–
6.
A
21.
D
36.
D
51.
–
7.
D
22.
B
37.
D
52.
–
8.
B
23.
A
38.
D
53.
–
9.
D
24.
D
39.
A
54.
–
10.
B
25.
C
40.
B
55.
–
11.
D
26.
C
41.
–
56.
–
12.
C
27.
A
42.
–
57.
–
13.
C
28.
A
43.
–
58.
–
14.
A
29.
B
44.
–
59.
–
15.
C
30.
A
45.
–
60.
–
N14/4/CHEMI/HP2/ENG/TZ0/XX
88146102
CHEMISTRY
HIGHER LEVEL
PAPER 2
Candidate session number
Examination code
Tuesday 18 November 2014 (afternoon)
8
2 hours 15 minutes
8
1
4
–
6
1
0
2
INSTRUCTIONS TO CANDIDATES
•
•
•
•
•
•
•
•
Write your session number in the boxes above.
Do not open this examination paper until instructed to do so.
Section A: answer all questions.
Section B: answer two questions.
Write your answers in the boxes provided.
A calculator is required for this paper.
A clean copy of the Chemistry Data Booklet is required for this paper.
The maximum mark for this examination paper is [90 marks].
31 pages
© International Baccalaureate Organization 2014
32EP01
N14/4/CHEMI/HP2/ENG/TZ0/XX
–2–
SECTION A
Answer all questions. Write your answers in the boxes provided.
1.
A student used a pH meter to measure the pH of different samples of water at 298 K.
Sample
(a)
pH ± 0.1
Rain water
5.1
River water
4.4
Tap water
6.5
Bottled water
7.1
Use the data in the table to identify the most acidic water sample.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
Calculate the percentage uncertainty in the measured pH of the rain water sample.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (c)
Determine the ratio of [H+] in bottled water to that in rain water.
[H+] in bottled water
__________________
[H+] in rain water
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
32EP02
–3–
N14/4/CHEMI/HP2/ENG/TZ0/XX
(Question 1 continued)
(d)
[2]
Determine the concentration of hydroxide ions in the sample of river water.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (e)
The acidity of non-polluted rain water is caused by dissolved carbon dioxide. State an
equation for the reaction of carbon dioxide with water.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
32EP03
N14/4/CHEMI/HP2/ENG/TZ0/XX
–4–
2.
The reaction between ethene and steam is used in the industrial production of ethanol.
C2H4 (g) + H2O (g) → C2H5OH (g)
The enthalpy change of the reaction can be calculated either by using average bond enthalpies
or by using standard enthalpies of formation.
(a)
Determine the enthalpy change of the reaction, in kJ mol–1, using the average bond
enthalpies in Table 10 of the Data Booklet.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
(i)
Define the term standard enthalpy change of formation.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
32EP04
N14/4/CHEMI/HP2/ENG/TZ0/XX
–5–
(Question 2 continued)
(ii)
Determine the enthalpy change of the reaction, in kJ mol–1, between ethene and
steam using the enthalpy change of formation values given below.
Ö
Compound
∆Hf / kJ mol–1
C2H5OH (g)
–235
C2H4 (g)
+52
H2O (g)
–242
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (c)
Comment on which of the values obtained in (a) and (b)(ii) is more accurate, giving
a reason.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (d)
[1]
Predict the sign of the entropy change of the reaction, ΔS, giving a reason.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
32EP05
N14/4/CHEMI/HP2/ENG/TZ0/XX
–6–
The vapour pressure of water changes with temperature according to the graph below.
200
180
160
Vapour pressure / kPa
3.
140
120
100
80
60
40
20
0
(a)
0
20
40
60
80
°
Temperature / C
100
120
A liquid boils when its vapour pressure equals atmospheric pressure. Determine the
boiling point of water on a mountaintop on a day when the atmospheric pressure is
60.0 kPa.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
Sketch another curve on the axes above to show how the vapour pressure of a
liquid that has weaker intermolecular forces than water, such as bromine, changes with
temperature.
[1]
(This question continues on the following page)
32EP06
–7–
N14/4/CHEMI/HP2/ENG/TZ0/XX
(Question 3 continued)
(c)
(i)
A sample of liquid bromine was left in a closed conical (Erlenmeyer) flask at 298 K
and allowed to reach a state of equilibrium. State an observation that indicates that
equilibrium was reached.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
The temperature of the closed flask was increased and the system was allowed to
reach a new equilibrium. Compare the equilibrium formed at the new temperature
with the equilibrium at the original temperature on the molecular level.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
32EP07
–8–
4.
N14/4/CHEMI/HP2/ENG/TZ0/XX
Phosphorus(V) oxide, P4O10 (M r = 283.88), reacts vigorously with water (M r = 18.02),
according to the equation below.
P4O10 (s) + 6H2O (l) → 4H3PO4 (aq)
(a)
A student added 5.00 g of P4O10 to 1.50 g of water. Determine the limiting reactant,
showing your working.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
Calculate the mass of phosphoric(V) acid, H3PO4 , formed in the reaction.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (c)
Phosphoric(V) acid, H3PO4 , has a pKa of 2.12 (pKa1) while phosphoric(III) acid, H3PO3 ,
has a pKa of 1.23 (pKa1). Identify the weaker of the two acids, giving a reason for
your choice.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (d)
State a balanced equation for the complete reaction of solid phosphorus(V) chloride,
PCl5, with water, including state symbols.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32EP08
[2]
–9–
5.
N14/4/CHEMI/HP2/ENG/TZ0/XX
Graphite has a layered structure of carbon atoms. A section of the structure is shown below.
Layer 1
335 pm
Layer 2
142 pm
Layer 3
(a)
Identify the type of attraction represented by the dotted lines shown between the layers.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
Graphite is used as a lubricant. Discuss two other uses of graphite with reference to its
layered structure.
[4]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
32EP09
N14/4/CHEMI/HP2/ENG/TZ0/XX
– 10 –
6.
The open-chain structure of D-fructose is shown below.
CH2OH
C
O
HO
C
H
H
C
OH
H
C
OH
CH2OH
(a)
State the names of two functional groups in D-fructose.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
Deduce the empirical formula of D-fructose.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (c)
Calculate the percentage composition by mass of D-fructose.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32EP10
[2]
N14/4/CHEMI/HP2/ENG/TZ0/XX
– 11 –
7.
The Contact process involves an exothermic reversible reaction.
Kc  1 at 200 °C and 1 atm
2SO2 (g) + O2 (g)  2SO3 (g)
(a)
[1]
Deduce the extent of the reaction at 200 °C and 1 atm.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
An engineer at a Contact process plant hypothesized that using pure oxygen, instead
of air, would increase the profits. Comment on whether or not her hypothesis is valid,
giving your reasons.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
32EP11
N14/4/CHEMI/HP2/ENG/TZ0/XX
– 12 –
SECTION B
Answer two questions. Write your answers in the boxes provided.
8.
A sample of magnesium contains three isotopes: magnesium-24, magnesium-25 and
magnesium-26, with abundances of 77.44 %, 10.00 % and 12.56 % respectively.
(a)
(i)
Calculate the relative atomic mass of this sample of magnesium correct to two
decimal places.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Predict the relative atomic radii of the three magnesium isotopes, giving your
reasons.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
32EP12
N14/4/CHEMI/HP2/ENG/TZ0/XX
– 13 –
(Question 8 continued)
(b)
A graph of the successive ionization energies of magnesium is shown below.
200 000
Ionization energy / kJ mol–1
160 000
120 000
80 000
40 000
0
(i)
0
1
2
3
4
5
6
7
8
Electron removed
9
10
11
12
Explain the increase in ionization energy values from the 3rd to the 8th electrons.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Explain the sharp increase in ionization energy values between the 10th and
11th electrons.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
32EP13
– 14 –
N14/4/CHEMI/HP2/ENG/TZ0/XX
(Question 8 continued)
(c)
(i)
Magnesium reacts with oxygen to form an ionic compound, magnesium oxide.
Describe how the ions are formed, and the structure and bonding in magnesium
oxide.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Carbon reacts with oxygen to form a covalent compound, carbon dioxide. Describe
what is meant by a covalent bond.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) State why magnesium and oxygen form an ionic compound while carbon and
oxygen form a covalent compound.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
32EP14
– 15 –
N14/4/CHEMI/HP2/ENG/TZ0/XX
(Question 8 continued)
(d)
(i)
[2]
Predict the type of hybridization of the carbon and oxygen atoms in CO2.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Sketch the orbitals of an oxygen atom in CO2 on the energy level diagram provided,
including the electrons that occupy each orbital.
Energy
[2]
Energy
2p
2s
Before hybridization
After hybridization
(iii) Define the term electronegativity.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [2]
(iv) Explain why oxygen has a larger electronegativity than carbon.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
32EP15
N14/4/CHEMI/HP2/ENG/TZ0/XX
– 16 –
(Question 8 continued)
(e)
The graph below shows pressure and volume data collected for a sample of
carbon dioxide gas at 330 K.
Pressure / × 105 Pa
25
X
20
15
10
5
0
0
50
100 150 200 250 300 350 400 450
Volume / × 10–6 m3
(i)
Draw a best-fit curve for the data on the graph.
[1]
(ii)
Use the data point labelled X to determine the amount, in mol, of carbon dioxide
gas in the sample.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(This question continues on the following page)
32EP16
– 17 –
N14/4/CHEMI/HP2/ENG/TZ0/XX
(Question 8 continued)
(f)
(i)
[2]
Most indicators are weak acids. Describe qualitatively how indicators work.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Identify a suitable indicator for a titration between a weak acid and a strong base,
using Table 16 of the Data Booklet.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
32EP17
N14/4/CHEMI/HP2/ENG/TZ0/XX
– 18 –
9.
Consider the following list of organic compounds.
Compound 1: CH3CH2CH(OH)CH3
Compound 2: CH3CH2COCH3
Compound 3: CH3CH2CH2OH
Compound 4: CH3CH2CH2CHO
(a)
(b)
Apply IUPAC rules to state the names of the four compounds.
Compound
Name
CH3CH2CH(OH)CH3
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CH3CH2COCH3
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CH3CH2CH2OH
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CH3CH2CH2CHO
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (i)
Define the term structural isomers.
[4]
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Identify the two compounds in the list that are structural isomers of each other.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
32EP18
N14/4/CHEMI/HP2/ENG/TZ0/XX
– 19 –
(Question 9 continued)
(c)
(i)
(ii)
Determine the organic product formed when each of the compounds is heated under
reflux with excess acidified potassium dichromate(VI). If no reaction occurs write
NO REACTION in the table.
Compound
Organic product
CH3CH2CH(OH)CH3
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CH3CH2COCH3
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CH3CH2CH2OH
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CH3CH2CH2CHO
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
[4]
[1]
Describe the colour change during the reactions that occur in part (i).
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (d)
Deduce the two-stage reaction pathway for converting 1-bromobutane into 1-pentanamine
(1-pentylamine). Include reagents and structural formulas of organic products for
each stage.
Reagent
Product
Stage 1
. . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . .
Stage 2
. . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . .
[4]
(This question continues on the following page)
Turn over
32EP19
– 20 –
N14/4/CHEMI/HP2/ENG/TZ0/XX
(Question 9 continued)
(e)
Explain the mechanism for the elimination of HBr from 1-bromobutane. Use curly
arrows to represent the movement of electron pairs.
(f)
(i)
Pentanoic acid reacts with ethanol. State the structural formula of the organic
product and the name of the functional group it contains.
[4]
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
State the type of reaction in part (i).
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (g)
Describe what is meant by a weak Brønsted–Lowry base, including an equation for the
reaction of ammonia with water.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32EP20
[3]
– 21 –
N14/4/CHEMI/HP2/ENG/TZ0/XX
Please do not write on this page.
Answers written on this page
will not be marked.
Turn over
32EP21
N14/4/CHEMI/HP2/ENG/TZ0/XX
– 22 –
10.
Iron rusts in the presence of oxygen and water. Rusting is a redox process involving
several steps that produces hydrated iron(III) oxide, Fe2O3 •nH2O, as the final product. The half-equations involved for the first step of rusting are given below.
(a)
(i)
Half-equation 1:
Fe (s) → Fe2+ (aq) + 2e–
Half-equation 2:
O2 (aq) + 4e– + 2H2O (l) → 4OH– (aq)
Identify whether half-equation 1 represents oxidation or reduction, giving a reason
for your answer.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Identify the oxidation number of each atom in the three species in half-equation 2.
[2]
O2 (aq) + 4e– + 2H2O (l) → 4OH– (aq)
(iii) Deduce the overall redox equation for the first step of rusting by combining
half-equations 1 and 2.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv) Identify the reducing agent in the redox equation in part (iii).
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
32EP22
– 23 –
N14/4/CHEMI/HP2/ENG/TZ0/XX
(Question 10 continued)
(b)
The oxygen in half-equation 2 is atmospheric oxygen that is found dissolved in water in
very small concentrations. Explain, in terms of intermolecular forces, why oxygen is not
very soluble in water.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (c)
State the relationship between the electron arrangement of an element and its group
and period in the periodic table.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (d)
Transition metals and their compounds often catalyse reactions. The catalyzed
decomposition of hydrogen peroxide by CuO is an example. State two other examples
of catalyzed reactions giving the transition metal or its compound acting as catalyst.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (e)
(i)
State a chemical equation for the partial dissociation of water into ions, including
state symbols.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
32EP23
– 24 –
N14/4/CHEMI/HP2/ENG/TZ0/XX
(Question 10 continued)
(ii)
The dissociation of water into ions is reversible. State the expression for the ionic
product constant of water.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii) The ionic product constant of water was measured at three different temperatures.
Temperature / K
Kw
298
1.00 × 10–14
313
2.92 × 10–14
373
5.13 × 10–13
Deduce whether the ionization of water is exothermic or endothermic, giving your
reason.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv) Use the data in part (iii) to determine the pH of water at 373 K, correct to two
decimal places.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
32EP24
– 25 –
N14/4/CHEMI/HP2/ENG/TZ0/XX
(Question 10 continued)
(f)
(i)
An aqueous solution of sodium chloride is electrolysed using inert electrodes. Explain
which product is obtained at the positive electrode (anode) if the concentration of
sodium chloride is high.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
State the half-equations occurring at the electrodes during the electrolysis of the
concentrated aqueous solution of sodium chloride.
[2]
Negative electrode (cathode):
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Positive electrode (anode):
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (g)
Describe how electrolysis can be used to electroplate a bracelet with a layer of silver
metal. Include the choice of electrodes and electrolyte needed in your description.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
32EP25
N14/4/CHEMI/HP2/ENG/TZ0/XX
– 26 –
Hydrogen peroxide decomposes according to the equation below.
2H2O2 (aq) → 2H2O (l) + O2 (g)
The rate of the decomposition can be monitored by measuring the volume of oxygen gas
released. The graph shows the results obtained when a solution of hydrogen peroxide
decomposed in the presence of a CuO catalyst.
70
60
Volume of oxygen / cm3
11.
50
40
30
20
10
0
0
10 20 30 40 50 60 70 80 90 100 110 120 130
Time / s
(a)
(i)
Outline how the initial rate of reaction can be found from the graph.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
32EP26
– 27 –
N14/4/CHEMI/HP2/ENG/TZ0/XX
(Question 11 continued)
(ii)
[3]
Explain how and why the rate of reaction changes with time.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
A Maxwell–Boltzmann energy distribution curve is drawn below. Label both axes and
explain, by annotating the graph, how catalysts increase the rate of reaction.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
32EP27
N14/4/CHEMI/HP2/ENG/TZ0/XX
– 28 –
(Question 11 continued)
(c)
(i)
In some reactions, increasing the concentration of a reactant does not increase
the rate of reaction. Describe how this may occur.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Consider the reaction
2A+B→C+D
The reaction is first order with respect to A, and zero order with respect to B.
Deduce the rate expression for this reaction.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (d)
[1]
Sketch a graph of rate constant (k) versus temperature.
k
T
(This question continues on the following page)
32EP28
N14/4/CHEMI/HP2/ENG/TZ0/XX
– 29 –
(Question 11 continued)
(e)
Hydrochloric acid neutralizes sodium hydroxide, forming sodium chloride and water.
NaOH (aq) + HCl (aq) → NaCl (aq) + H2O (l)
(i)
ΔH À = –57.9 kJ mol
–1
Define standard enthalpy change of reaction, ΔH À.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Determine the amount of energy released, in kJ, when 50.0 cm3 of 1.00 mol dm–3
sodium hydroxide solution reacts with 50.0 cm3 of 1.00 mol dm–3 hydrochloric
acid solution.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
32EP29
– 30 –
N14/4/CHEMI/HP2/ENG/TZ0/XX
(Question 11 continued)
(iii) In an experiment, 2.50 g of solid sodium hydroxide was dissolved in 50.0 cm3
of water. The temperature rose by 13.3 °C. Calculate the standard enthalpy change,
in kJ mol–1, for dissolving one mole of solid sodium hydroxide in water.
NaOH (s) → NaOH (aq)
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv) Using relevant data from previous question parts, determine ΔH À, in kJ mol–1, for
the reaction of solid sodium hydroxide with hydrochloric acid.
NaOH (s) + HCl (aq) → NaCl (aq) + H2O (l)
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
32EP30
– 31 –
N14/4/CHEMI/HP2/ENG/TZ0/XX
(Question 11 continued)
(f)
(i)
Zinc is found in the d-block of the periodic table. Explain why it is not considered
a transition metal.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Explain why Fe3+ is a more stable ion than Fe2+ by reference to their electron
configurations.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32EP31
[3]
Please do not write on this page.
Answers written on this page
will not be marked.
32EP32
N14/4/CHEMI/HP2/ENG/TZ0/XX/M
MARKSCHEME
November 2014
CHEMISTRY
Higher Level
Paper 2
16 pages
–2–
N14/4/CHEMI/HP2/ENG/TZ0/XX/M
It is the property of the International Baccalaureate and must not
be reproduced or distributed to any other person without the
authorization of the IB Assessment Centre.
–3–
N14/4/CHEMI/HP2/ENG/TZ0/XX/M
Subject Details: Chemistry HL Paper 2 Markscheme
Mark Allocation
Candidates are required to answer ALL questions in Section A [40 marks] and TWO questions in
Section B [2 x 25 marks]. Maximum total = [90 marks].
1.
A markscheme often has more marking points than the total allows. This is intentional.
2.
Each marking point has a separate line and the end is shown by means of a semicolon (;).
3.
An alternative answer or wording is indicated in the markscheme by a slash (/). Either wording can
be accepted.
4.
Words in brackets ( ) in the markscheme are not necessary to gain the mark.
5.
Words that are underlined are essential for the mark.
6.
The order of marking points does not have to be as in the markscheme, unless stated otherwise.
7.
If the candidate’s answer has the same “meaning” or can be clearly interpreted as being of
equivalent significance, detail and validity as that in the markscheme then award the mark.
Where this point is considered to be particularly relevant in a question it is emphasized by
OWTTE (or words to that effect).
8.
Remember that many candidates are writing in a second language. Effective communication is more
important than grammatical accuracy.
9.
Occasionally, a part of a question may require an answer that is required for subsequent
marking points. If an error is made in the first marking point then it should be penalized. However,
if the incorrect answer is used correctly in subsequent marking points then follow through marks
should be awarded. When marking, indicate this by adding ECF (error carried forward) on the script.
10.
Do not penalize candidates for errors in units or significant figures, unless it is specifically referred
to in the markscheme.
11.
If a question specifically asks for the name of a substance, do not award a mark for a correct formula
unless directed otherwise in the markscheme. Similarly, if the formula is specifically asked for,
unless directed otherwise in the markscheme, do not award a mark for a correct name.
12.
If a question asks for an equation for a reaction, a balanced symbol equation is usually expected, do
not award a mark for a word equation or an unbalanced equation unless directed otherwise in the
markscheme.
13.
Ignore missing or incorrect state symbols in an equation unless directed otherwise in the
markscheme.
–4–
N14/4/CHEMI/HP2/ENG/TZ0/XX/M
SECTION A
1.
(a)
river (water);
[1]
(b)
 0.1

 100   2% ;
 5.1

[1]
recognition that values differ by 2 pH units / calculation of both [H+] values;
1
(ratio  )1:100 /
/10 2 /0.01 ;
100
Award [2] for correct final answer.
Award [1 max] for 100:1/100/102.
[2]
(c)
(d)
pOH  (14.0  4.4 )9.6 / [H  ]  4 105 (mol dm3 ) ;
+
–5
–3
Accept [H ] = 3.98×10 (mol dm ) .
[OH– ] = 3×10–10 (moldm–3 ) ;
Accept 2.51×10 –10 (mol dm–3 ) .
[2]
Award [2] for correct final answer.
2.
(e)
CO 2  H 2 O  HCO3  H  / CO 2  2H 2 O  HCO3  H 3O  / CO 2  H 2O  H 2 CO3 ;
Do not penalize missing reversible arrow.
Do not accept equations with the carbonate ion as a product.
(a)
(bonds broken) C=C and O–H / 612  464 / 1076 ;
(bonds formed) C–C and C–H and C–O / 347  413  358 / 1118 ;
[1]
OR
(bonds broken) C=C and two O–H and four C–H / 612  4(413)  2(464) / 3192 ;
(bonds formed) C–C and five C–H and C–O and O–H / 347  5(413)  358  464
/ 3234 ;
Ignore signs (+ and –) in M1 and M2.
recognizing the correct bonds.
These two marks are awarded for
enthalpy change  42(kJ) ;
Correct sign is necessary for awarding M3.
Award [3] for the correct final answer.
Do not penalize candidates using the former Data Booklet bond energy values
(348, 412 and 463) (final answer will then be -45(kJ)).
[3]
–5–
(b)
(i)
N14/4/CHEMI/HP2/ENG/TZ0/XX/M
heat/enthalpy change when 1 mol of a compound/substance is formed;
5
from its elements in their standard states/at 100kPa/10 Pa ;
[2]
Allow 1.01 10 Pa/101kPa/1atm as an alternative to 100 kPa/10 Pa.
Allow under standard conditions or standard ambient temperature and
pressure as an alternative to 100 kPa/105 Pa.
Allow “energy needed/absorbed” as an alternative to “heat/enthalpy
change”.
Temperature is not required in definition, allow if quoted (eg, 298K / 25 C) .
5
(ii)
(c)
3.
5
(235)  (52  242) / H  H f Ö (products)  H f Ö (reactants) ;
45(kJ) ;
Award [2] for the correct final answer.
Award [1] for +45 or 45.
[2]
value in (b)(ii) (is more accurate) as values used in (a) are average values / value in
(b)(ii) (is more accurate) as exact bond enthalpy depends on the surroundings of the
bond / OWTTE;
[1]
(d)
negative and fewer number of moles/molecules (of gas);
[1]
(a)
87 (C) ;
Accept boiling points in the range 86  88 C .
[1]
(b)
similar shape above current curve / steeper than current curve;
Do not penalize if curves meet at 0 °C.
[1]
(c)
(i)
(intensity of) colour of vapour is constant;
Accept volume/level of liquid is constant.
Allow pressure is constant.
[1]
(ii)
more (molecules in the) vapour / fewer molecules in the liquid at new
equilibrium / OWTTE;
molecules have more energy/move faster/collide more frequently at the new
temperature / OWTTE;
rates of evaporation and condensation are higher at the new temperature;
[2 max]
in both flasks the rates of evaporation and condensation are equal;
Accept converse points for the flask at lower temperature for M1, M2 and M3.
–6–
4.
(a)
N14/4/CHEMI/HP2/ENG/TZ0/XX/M
 1.50 
 5.00 
  0.0832(mol) ;
P4 O10 : 
  0.0176 (mol) and H 2 O : 
 18.02 
 283.88 
H 2O is the limiting reactant and reason related to stoichiometry;
0.0832  4
/ 0.0555(mol) ;
6
(0.0555  98.00 )5.44g ;
The unit is needed for M2.
Award [2] for correct final answer.
Do not penalize slight numerical variations due to premature rounding.
[2]
(c)
H3PO4 is the weaker acid and higher pKa/lower Ka;
[1]
(d)
PCl5 (s)  4H2O(l)  H3PO4 (aq)  5HCl(g)
(b)
correct products and balancing;
correct state symbols;
Accept (aq) for HCl or H+ and Cl– ions.
M2 can only be awarded if M1 correct.
Allow PCl5 (s)+ H 2O(l)  POCl3 (g)+2HCl (g) .
5.
[2]
(a)
(b)
van der Waals’/vdW/London/dispersion (forces)/LDF / temporary/instantaneous/
induced dipoles;
[2]
[1]
Two of the following pairs:
used as pencil (lead);
layers can flake off/slide off/break off/stick to paper / OWTTE;
M2 must contain concept of separation of layers, so do not award mark for phrases
like "layers can slide over each other" on their own.
OR
used as carbon fibre / OWTTE;
bonding within layer is strong / layers are extensive / layers are strong;
OR
used as electrodes/conductor/in batteries;
has mobile/free/delocalized electrons (between layers) / electricity flows parallel to
layers;
OR
used for thermal insulation;
vibrations are not easily passed between layers;
Accept other valid uses of graphite along with a suitable explanation.
[4 max]
–7–
6.
(a)
hydroxyl and carbonyl;
Accept alcohol as an alternative to hydroxyl and/or ketone as an alternative to
carbonyl.
Allow hydroxy, but not hydroxide, as an alternative to hydroxyl.
[1]
(b)
CH2O ;
[1]
(c)
7.
N14/4/CHEMI/HP2/ENG/TZ0/XX/M
(a)
(b)
 12.01

C:
100   39.99/40.0%
 30.03

 2.02

H: 
100   6.73/6.7 %
 30.03

 16.00

O:
100   53.28/53.3% ;;
[2]
 30.03

Award [2] if all three are correct, and [1] if two are correct.
Accept if the third value is obtained by subtracting the other two percentages from 100%.
Do not penalize if integer values of relative atomic masses are used.
concentration of products is much higher than the concentration of reactants /
reaction nearly/almost goes to completion / position of equilibrium lies very far to
the right / OWTTE;
Response must indicate the position of equilibrium is far to the right, but not
complete conversion.
[1]
(hypothesis is not valid as) equilibrium already nearly goes to completion /
OWTTE;
(hypothesis is not valid as increase in yield may not be worth) expense of using
pure oxygen / OWTTE;
(hypothesis is valid as pure oxygen) increases the rate of (the forward) reaction /
more SO3 produced per day/hour;
(hypothesis is valid as pure oxygen) shifts equilibrium to the right/products/SO3 /
[2 max]
increases the equilibrium concentration of SO3;
Award [1 max] if no reference to “hypothesis’.
–8–
N14/4/CHEMI/HP2/ENG/TZ0/XX/M
SECTION B
8.
(a)
(i)
(ii)
(b)
(i)
(ii)
(c)
 (77.44  24)  (10.00  25)  (12.56  26) 

;
100


24.35;
Award [2] for correct final answer.
Two decimal places are required for M2.
Do not award any marks for 24.31 without showing method (as the value can
be copied from the Data Booklet).
same atomic radii / 160 pm;
isotopes only differ by number of neutrons/size of nucleus / radius determined
by electron shells and number of protons / OWTTE;
Accept neutrons do not affect distance of electrons / OWTTE.
decreasing repulsion between electrons / radius decreases as electrons are
removed;
Accept increasing positive charge on ion attracts electrons more strongly.
10th electron is in second energy level/shell while 11th electron is in first
energy level/shell / 10th is removing electron from electronic arrangement 2,1
while 11th ionization energy is removing electron from electronic
arrangement 2;
11th electron removed is much closer to the nucleus / 11th electron removed
from a (much) lower energy level/shell;
Accept opposite statement for 10th electron.
[2]
[2]
[1]
[2]
(i)
magnesium (atom) gives two electrons to oxygen (atom) / oxygen (atom)
takes two electrons from magnesium (atom) / magnesium (atom) loses two
electrons and oxygen (atom) gains two electrons;
3-dimensional/3-D arrangement of ions / lattice of ions;
(electrostatic) attraction between oppositely charged ions/Mg2+ and O2–;
[2 max]
(ii)
electrostatic attraction between a pair of electrons and (positively charged)
nuclei;
Accept a/two pairs of shared electrons.
[1]
(iii) difference in electronegativity is larger between Mg and O/smaller between C
and O;
Accept reference to a numerical value of difference in electronegativity such
as above and below 1.80.
[1]
–9–
(d)
(i)
(ii)
N14/4/CHEMI/HP2/ENG/TZ0/XX/M
C: sp hybridization;
O: sp2 hybridization;
Award [1] if the answer is sp without specifying C or O atoms.
Energy
Energy
2p
2p
2s
sp2
Before hybridization
After hybridization
three sp2 orbitals and one p-orbital at higher energy;
sp2 orbitals contain: two, two and one electron and p-orbital contains one
electron;
Do not allow ECF from (d)(i).
(e)
[2]
[2]
(iii) ability of atom/nucleus to attract bonding/shared pair of electrons / attraction
of nucleus for bonding/shared pair of electrons / OWTTE;
[1]
(iv) (same number of shells but) increase in nuclear charge/atomic
number/number of protons increases electronegativity / O has more protons
than C;
Accept oxygen has a higher effective nuclear charge.
decrease in radius along the period increases electronegativity / O has smaller
radius than C;
[2]
(i)
smooth curve through the data;
Do not accept a curve that passes through all of the points or an answer that
joins the points using lines.
[1]
(ii)
p  21105 /2.1106 (Pa) / 2.1103 (kPa) and
V  50 106 /5.0 105 (m3 ) / 5.0 102 (dm3 ) ;
pV  2.1106  5.0 105

n


;

RT 
8.31 330

n  0.038(mol) ;
[3]
Award [3] for correct final answer.
For M3 apply ECF for correct computation of the equation the student has
written, unless more than one mistake is made prior this point.
(f)
(i)
equilibrium between HIn and In  / HIn  In   H  ;
the colours of HIn and In– are different;
if added to acid, the equilibrium shifts to the left and the colour of HIn is seen
/ OWTTE;
if added to base/alkali, the equilibrium shifts to the right and the colour of In–
[2 max]
is seen / OWTTE;
(ii)
phenolphthalein;
Accept phenol red.
[1]
– 10 –
9.
(a)
Compound
Name
CH3CH2CH(OH)CH3
CH3CH2CH2OH
butan-2-ol/2-butanol;
butanone;
Accept butan-2-one and 2-butanone.
propan-1-ol/1-propanol;
CH3CH2CH2CHO
butanal;
CH3CH2COCH3
(b)
(c)
N14/4/CHEMI/HP2/ENG/TZ0/XX/M
[4]
(i)
same molecular formula but differ in arrangement of their atoms;
Allow “different structures/structural formulas” instead of “different
arrangement of atoms”.
[1]
(ii)
(compounds) 2 and 4 / butanone and butanal;
[1]
(i)
(ii)
Compound
Organic Product
CH3CH2CH(OH)CH3
butanone/CH3CH2COCH3;
CH3CH2COCH3
no reaction;
CH3CH2CH2OH
propanoic acid/CH3CH2COOH;
CH3CH2CH2CHO
butanoic acid/CH3CH2CH2COOH;
orange to green;
(d)
[1]
Reagent
Product
–
CN / NaCN / KCN / HCN;
CH3CH2CH2CH2CN;
H2 (with Ni/Pd/Pt catalyst) /
CH3CH2CH2CH2CH2NH2;
Stage 2
LiAlH4;
Accept formulas or names of reagents but only structural formulas (condensed or
displayed) of products.
Penalize wrong bonding and/or missing hydrogens once only.
Accept other valid reduction reagents for Stage 2 such as hydrides.
Stage 1
[4]
[4]
– 11 –
N14/4/CHEMI/HP2/ENG/TZ0/XX/M
(e)
curly arrow going from lone pair/negative charge on O in HO– to H on β–C;
Do not allow curly arrow originating on H in HO–.
Accept mechanism with an alkoxide ion (eg RO– / ethoxide/CH3CH2O–) rather than HO– acting
as the base.
curly arrow going from CH bond to form C=C bond;
curly arrow showing Br leaving;
formation of organic product H2C=CH(C2H5) and H2O and Br-;
Penalize missing hydrogens or incorrect bond linkages once only.
Allow E1 mechanism:
H
H
H
H
H
C
C
C
C
Br
H
H
H
H
H
H
H
H
H
C
C
C
C
H
H
H
H
+
Br–
OH
H
H
C
H
+
C
H2O
C2H5
curly arrow showing Br leaving;
representation of carbocation;
curly arrow going from lone pair on O in HO– to H on C adjacent to C+ and curly
arrow going from CH bond to form C=C bond;
formation of organic product H2C=CH(C2H5) and H2O and Br– (somewhere in
mechanism);
(f)
(i)
(ii)
(g)
CH3CH2CH2CH2COOCH2CH3;
ester;
condensation / addition-elimination;
Accept esterification.
a base is a proton acceptor;
weak means it is only partially ionized/dissociated (in solution/water);
NH 3  H 2 O  NH 4   OH  ;
Reversible arrow is required for M3.
[4]
[2]
[1]
[3]
– 12 –
10.
(a)
N14/4/CHEMI/HP2/ENG/TZ0/XX/M
(i)
oxidation and (iron/Fe) loses electrons/increases in oxidation number/state;
(ii)
O2 (aq)  4e  2H 2O (l)  4OH  (aq)
0
I
–II
–II I
;;
[1]
[2]
Award [2] for five correct.
Award [1] for four correct.
Accept use of oxidation states (0, +1, –2, –2, +1) for oxidation numbers.
Penalize once for incorrect notation (eg, 2, 2–).
(iii) O 2 (aq)  2H 2O (l)  2Fe (s)  2Fe 2 (aq)  4 OH  (aq) ;
Ignore state symbols.
[1]
(iv) Fe/iron;
[1]
(b)
oxygen is non-polar;
needs to break strong hydrogen bonds/H–bonds between water molecules (to
dissolve) / oxygen cannot form hydrogen bonds/H–bonds with water;
oxygen can only form (weak) van der Waals’/vdW/LDF/London/dispersion forces
with water;
[2 max]
(c)
groups indicate the number of electrons in the highest energy level/outer/valence
shell;
periods indicate the number of (occupied) energy levels/shells (in the atom);
[2]
(d)
V2O5 catalyses oxidation of SO2 / V2O5 is a catalyst in the Contact Process;
Fe catalyses the reaction between N2 and H2 / Fe is a catalyst in the Haber Process;
Ni/Pd/Pt catalyses hydrogenation / manufacture of margarine / addition of hydrogen
to C=C / conversion of alkenes to alkanes;
Pd/Pt is a catalyst in catalytic converters / Pd/Pt catalyzes reaction of NO2 and
CO/NO2 and (unburnt) fuel/exhaust gases;
[2 max]
Accept other correct examples.
Accept formulas or names of substances.
(e)
(i)
H 2 O (l)  H  (aq)  OH  (aq) / 2H 2 O (l)  H 3O  (aq)  OH  (aq) ;
 and state symbols are necessary for the mark.
[1]
(ii)
K W  [H  ][OH  ] / K W  [H 3O  ][OH  ] ;
[1]
(iii) at higher temperatures ionization increases / at higher temperatures
equilibrium shifts to right;
ionization is endothermic;
Do not allow ECF for M2.
(iv)
5.13 1013  [H3 O  ]2 /[H  ]2 / [H 3 O  ] / [H  ]  7.16 107 (mol dm 3 ) ;
pH  6.14/6.15 ;
Award [2] for correct final answer.
[2]
[2]
– 13 –
(f)
(i)
(ii)
N14/4/CHEMI/HP2/ENG/TZ0/XX/M
chlorine/Cl2 (is produced at the positive electrode/anode);
according to electrochemical series/ E  values/ease of oxidation OH–/H2O
reacts/oxygen is released / OWTTE / at low chloride concentration OH–/H2O
reacts/oxygen is released;
high concentration makes Cl– oxidize/react in preference to OH–/H2O /
OWTTE;
[3]
Negative electrode (cathode):
2H  (aq)  2e   H 2 (g) / H  (aq)  e   12 H 2 (g) / 2H 2 O(l)  2 e  H 2 (g)  2OH  (aq) ;
Positive electrode (anode):
2Cl  (aq)  Cl2 (g)  2e  / Cl  (aq)  12 Cl2 (g)  e  / 2Cl (aq)  2e   Cl2 (g) /
Cl (aq)  e  12 Cl2 (g) ;
Ignore state symbols.
[2]
Accept e instead of e–.
Award [1] if half-equations are correct but placed at the wrong electrodes.
(g)
bracelet/object to be electroplated is the cathode/negative electrode;
silver anode/positive electrode;
Accept Pt anode.
Electrolyte: liquid Na[Ag(CN2)]/sodium dicyanoargentate/[Ag(CN)2]–/ solution of
an appropriate silver salt;
Accept AgNO3/silver nitrate.
All marks can be scored with a labelled diagram.
[3]
– 14 –
11.
(a)
(i)
(ii)
N14/4/CHEMI/HP2/ENG/TZ0/XX/M
(draw a) tangent to the curve at origin/time = 0/start of reaction;
(calculate) the gradient/slope (of the tangent);
rate decreases (with time);
concentration/number of (reactant) molecules per unit volume decreases (with
time);
Do not accept “number of molecules decreases” or “amount of reactant
decreases”.
collisions (between reactant molecules/reactant and catalyst) become less
frequent;
Do not accept “fewer collisions” without reference to frequency (eg, no.
collisions per second).
(b)
[2]
[3]
y-axis: probability / fraction of molecules/particles / probability density
Allow “number of particles/molecules” on y-axis.
and
x-axis: (kinetic) energy;
Accept “speed/velocity” on x-axis.
Probability
of
molecules
E a catalysed E a uncatalysed
(Kinetic) Ene rgy
correct relative position of Ea catalysed and Ea uncatalysed;
more/greater proportion of molecules/collisions have the lower/required/catalysed
Ea (and can react upon collision);
M3 can be scored by stating or shading and annotating the graph.
Accept “a greater number/proportion of successful collisions as catalyst reduces
Ea”.
(c)
(i)
(ii)
reactant not involved in (or before) the slowest/rate-determining step/RDS;
reactant is in (large) excess;
(rate )k [A] ;
[3]
[1 max]
[1]
Accept rate  k[A] [B] .
1
0
– 15 –
(d)
N14/4/CHEMI/HP2/ENG/TZ0/XX/M
curve with a positive slope curving upwards;
Do not penalize if curve passes through the origin.
[1]
k
T
(e)
(i)
heat transferred/absorbed/released/enthalpy/potential energy change when 1
mol/molar amounts of reactant(s) react (to form products) / OWTTE;
under standard conditions / at a pressure 100 kPa/101.3 kPa/1 atm and
temperature 298 K/25 C ;
Award [2] for difference between standard enthalpies of products and
standard enthalpies of reactants / H Ö (products) – H Ö (reactants).
Award [2] for difference between standard enthalpies of formation of
Ö
products and standard enthalpies of formation of reactants /  H f
[2]
(products) –  H Öf (reactants).
(ii)
(1.00  0.0500 ) 0.0500 (mol) ;
(0.0500  57.9 ) 2.90 (kJ) ;
Ignore any negative sign.
Award [2] for correct final answer.
Award [1 max] for 2900 J.
 2.50 
  0.0625(mol NaOH) ;
(iii) 
 40.00 
0.0500  4.18 13.3  2.78(kJ) / 50.0  4.18 13.3  2780(J) ;
 2.78 
1

  44.5(kJ mol ) ;
 0.0625 
Award [3] for correct final answer.
Negative sign is necessary for M3.
Award M2 and M3 if 52.5 g is used to obtain an enthalpy change of –46.7
(kJ mol-1).
[2]
[3]
– 16 –
(iv)
N14/4/CHEMI/HP2/ENG/TZ0/XX/M
 44.5  57.9 / correct Hess’s Law cycle (as below) / correct
manipulation of equations;
NaOH (s)  HCl(aq)  NaCl (aq)  H 2O (l)
–44.5 kJ
–57.9 kJ
NaOH (aq) + HCl (aq)
102.4 kJ ;
Award [2] for correct final answer.
(f)
(i)
(ii)
zinc (only) forms the ion Zn2+ / has the oxidation state +2;
Allow forms only one ion / has only one oxidation state.
has full d-subshell/orbitals / does not have a partially filled d-subshell/orbitals
(needed to exhibit transition metal properties);
Fe2+: 1s2 2s2 2p6 3s2 3p6 3d6 /[Ar] 3d6 and Fe3+: 1s2 2s2 2p6 3s2 3p6 3d5 /[Ar] 3d5;
half-full sub-level/3d5 has extra stability;
less repulsion between electrons / electrons singly occupy orbitals / electrons
do not have to pair with other electrons;
Accept converse points for Fe2+.
[2]
[2]
[3]
M15/4/CHEMI/HPM/ENG/TZ1/XX
Chemistry
Higher level
Paper 1
Thursday 14 May 2015 (afternoon)
1 hour
Instructions to candidates
• Do not open this examination paper until instructed to do so.
• Answer all the questions.
• For each question, choose the answer you consider to be the best and indicate your choice on
the answer sheet provided.
• The periodic table is provided for reference on page 2 of this examination paper.
• The maximum mark for this examination paper is [40 marks].
15 pages
2215 –6107
© International Baccalaureate Organization 2015
39
Y
88.91
12
Mg
24.31
20
Ca
40.08
38
Sr
87.62
11
Na
22.99
19
K
39.10
37
Rb
85.47
40
Zr
91.22
22
Ti
47.90
41
Nb
92.91
23
V
50.94
87
Fr
(223)
88
Ra
(226)
‡
†
89 ‡
Ac
(227)
90
91
Th
Pa
232.04 231.04
58
59
Ce
Pr
140.12 140.91
26
Fe
55.85
27
Co
58.93
28
Ni
58.71
29
Cu
63.55
30
Zn
65.37
6
C
12.01
14
Si
28.09
32
Ge
72.59
13
Al
26.98
31
Ga
69.72
4
5
B
10.81
3
33
As
74.92
15
P
30.97
7
N
14.01
5
34
Se
78.96
16
S
32.06
8
O
16.00
6
10
Ne
20.18
18
Ar
39.95
36
Kr
83.80
17
Cl
35.45
35
Br
79.90
84
Po
(210)
85
At
(210)
93
Np
(237)
94
Pu
(242)
95
Am
(243)
96
Cm
(247)
97
Bk
(247)
98
Cf
(251)
99
Es
(254)
100
Fm
(257)
101
Md
(258)
102
No
(259)
103
Lr
(260)
66
61
68
64
67
62
69
65
63
70
71
60
Dy
Pm
Sm
Tm
Tb
Lu
Nd
Er
Gd
Ho
Eu
Yb
144.24 146.92 150.35 151.96 157.25 158.92 162.50 164.93 167.26 168.93 173.04 174.97
92
U
238.03
2
He
4.00
0
9
F
19.00
7
86
Rn
(222)
45
48
43
50
46
49
44
54
51
47
52
53
In
I
Rh
Cd
Tc
Sn
Pd
Ru
Xe
Sb
Ag
Te
98.91 101.07 102.91 106.42 107.87 112.40 114.82 118.69 121.75 127.60 126.90 131.30
25
Mn
54.94
The Periodic Table
80
75
82
78
81
76
83
79
77
74
Re
Pb
Pt
Tl
Os
Bi
Au
W
Ir
Hg
183.85 186.21 190.21 192.22 195.09 196.97 200.59 204.37 207.19 208.98
42
Mo
95.94
24
Cr
52.00
Relative atomic mass
Element
Atomic number
56
57 †
72
73
55
Ba
La
Ta
Cs
Hf
132.91 137.34 138.91 178.49 180.95
21
Sc
44.96
4
Be
9.01
2
3
Li
6.94
1
H
1.01
1
–2–
M15/4/CHEMI/HPM/ENG/TZ1/XX
–3–
1.
M15/4/CHEMI/HPM/ENG/TZ1/XX
4.0 g of solid sodium hydroxide is added to 0.10 dm3 of 1.0 mol dm−3 aqueous sulfuric acid.
2NaOH (s) + H2SO4 (aq) → Na2SO4 (aq) + 2H2O (l)
Which statement is correct?
2.
3.
4.
A.
Neither reactant is in excess.
B.
0.10 mol Na2SO4 is formed.
C.
Excess H2SO4 remains in solution.
D.
Excess NaOH remains in solution.
Which compound has the highest percentage of carbon by mass?
A.
CH4
B.
C2 H 4
C.
C4H10
D.
C6 H 6
Which solution contains the biggest amount, in mol, of chloride ions?
A.
20 cm3 of 0.50 mol dm−3 NH4Cl
B.
60 cm3 of 0.20 mol dm−3 MgCl2
C.
70 cm3 of 0.30 mol dm−3 NaCl
D.
100 cm3 of 0.30 mol dm−3 ClCH2COOH
Ultraviolet radiation has a shorter wavelength than infrared radiation. How does the frequency and
energy of ultraviolet radiation compare with infrared radiation?
Frequency
Energy
A.
higher
higher
B.
higher
lower
C.
lower
higher
D.
lower
lower
Turn over
–4–
5.
M15/4/CHEMI/HPM/ENG/TZ1/XX
The first ionization energies (in kJ mol−1) of five successive elements in the periodic table are:
1314, 1681, 2081, 496 and 738
What could these elements be?
6.
7.
8.
A.
d-block elements
B.
The last two elements of one period and the first three elements of the next period
C.
The last three elements of one period and the first two elements of the next period
D.
The last five elements of a period
What is the total number of valence electrons in CH3COO−?
A.
16
B.
22
C.
23
D.
24
What is the definition of the term first ionization energy?
A.
The energy released when one mole of electrons is removed from one mole of gaseous
atoms.
B.
The energy required to remove one mole of electrons from one mole of gaseous atoms.
C.
The energy released when one mole of gaseous atoms gains one mole of electrons.
D.
The energy required to add one mole of electrons to one mole of gaseous atoms.
Which statements are correct about the complex [Cu (NH3)2Cl2]?
I.
Oxidation state of copper is +2.
II.
Ammonia is a ligand.
III.
Chloride ions act as Lewis acids.
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
–5–
9.
10.
M15/4/CHEMI/HPM/ENG/TZ1/XX
Which molecules react to form a dative covalent (coordinate) bond?
A.
CH4 and NH3
B.
C2H2 and Cl2
C.
NH3 and HF
D.
Cl2 and HF
The following compounds have similar molar masses:
CH3CH2COOH, CH3CH2CH2CH2OH and CH3CH2CH2CH2CH3
What is the order of increasing boiling points?
11.
A.
CH3CH2CH2CH2OH < CH3CH2COOH < CH3CH2CH2CH2CH3
B.
CH3CH2COOH < CH3CH2CH2CH2CH3 < CH3CH2CH2CH2OH
C.
CH3CH2COOH < CH3CH2CH2CH2OH < CH3CH2CH2CH2CH3
D.
CH3CH2CH2CH2CH3 < CH3CH2CH2CH2OH < CH3CH2COOH
Which substance has the following properties?
• Low melting point
• Very soluble in water
• Does not conduct electricity when molten
A.
Glucose, C6H12O6
B.
Silicon dioxide, SiO2
C.
Sodium chloride, NaCl
D.
Tetrachloromethane, CCl4
Turn over
–6–
12.
What is correct for PCl5?
Shape
13.
Bond angle(s)
90 and 180
A.
Octahedral
B.
Trigonal pyramidal
107
C.
Square pyramidal
90 and 180
D.
Trigonal bipyramidal
90, 120 and 180
Which molecules have sp2 hybridization?
I.
C 2H 4
II.
C4H10
III.
C6 H 6
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
M15/4/CHEMI/HPM/ENG/TZ1/XX
M15/4/CHEMI/HPM/ENG/TZ1/XX
–7–
14.
The same amount of heat energy is added to 1.00 g of each substance.
Substance
Specific heat capacity / J g−1 K−1
Copper
0.39
Aluminium
0.90
Sodium chloride
0.90
Water
4.18
Which statement is correct if all the substances are at the same temperature before the heat
energy is added?
15.
A.
Copper will reach the highest temperature.
B.
Water will reach the highest temperature.
C.
All four substances will reach the same temperature.
D.
Aluminium will reach a higher temperature than sodium chloride.
The heat change in a neutralization reaction can be determined by mixing equal volumes of
HCl (aq) and NaOH (aq) of the same concentration in a glass beaker. The maximum temperature
change is recorded using an alcohol thermometer.
What is the biggest source of error in this experiment?
16.
A.
Heat absorbed by the glass thermometer
B.
Random error in the thermometer reading
C.
Heat loss to the surroundings
D.
Systematic error in measuring the volumes of HCl (aq) and NaOH (aq) using burettes
Which equation represents the standard enthalpy of formation of liquid methanol?
A.
C (g) + 2H2 (g) + 21 O2 (g) → CH3OH (l)
B.
C (g) + 4H (g) + O (g) → CH3OH (l)
C.
C (s) + 4H (g) + O (g) → CH3OH (l)
D.
C (s) + 2H2 (g) + 21 O2 (g) → CH3OH (l)
Turn over
–8–
17.
18.
19.
M15/4/CHEMI/HPM/ENG/TZ1/XX
Which species are arranged in order of increasing entropy?
A.
C3H8 (g) < CH3OH (l) < Hg (l) < Na (s)
B.
CH3OH (l) < C3H8(g) < Hg (l) < Na (s)
C.
Na (s) < Hg (l) < CH3OH (l) < C3H8 (g)
D.
Na (s) < Hg (l) < C3H8 (g) < CH3OH (l)
Which combination of ∆H and ∆S values corresponds to a non-spontaneous reaction at all
temperatures?
∆H
∆S
A.
−
−
B.
+
−
C.
−
+
D.
+
+
Nitrogen gas reacts with hydrogen gas according to the following equation.
N2 (g) + 3H2 (g)  2NH3 (g)
∆H = − 92 kJ
Why is the rate of reaction slow at room temperature?
A.
The activation energy of the forward reaction is high.
B.
The activation energy of the forward reaction is low.
C.
The equilibrium constant is very small.
D.
The rate of the reverse reaction is greater than the rate of the forward reaction.
–9–
20.
21.
M15/4/CHEMI/HPM/ENG/TZ1/XX
Which statement about a first-order reaction is correct?
A.
The reactant concentration decreases linearly with time.
B.
The reactant concentration decreases exponentially with time.
C.
The rate of reaction remains constant as the reaction proceeds.
D.
The rate of reaction increases exponentially as the reaction proceeds.
Consider the rate expression:
Rate = k [X] [Y]
Which change decreases the value of the rate constant, k?
22.
A.
Increase in the reaction temperature
B.
Decrease in the reaction temperature
C.
Increase in the concentration of X and Y
D.
Decrease in the concentration of X and Y
Carbon monoxide and water react together in the industrial production of hydrogen gas.
CO (g) + H2O (g)  CO2 (g) + H2 (g)
What is the impact of decreasing the volume of the equilibrium mixture at a constant temperature?
A.
The amount of H2 (g) remains the same but its concentration decreases.
B.
The forward reaction is favoured.
C.
The reverse reaction is favoured.
D.
The value of Kc remains unchanged.
Turn over
– 10 –
23.
24.
25.
26.
M15/4/CHEMI/HPM/ENG/TZ1/XX
Which factors do not affect the vapour pressure of a liquid in equilibrium with its vapour in a
closed container?
I.
Volume of container
II.
Volume of liquid
III.
Temperature
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
Which gas in the atmosphere causes the pH of unpolluted rain to be approximately 6?
A.
Carbon dioxide
B.
Sulfur dioxide
C.
Oxygen
D.
Nitrogen
Which compound is a strong acid?
A.
NH3
B.
HNO3
C.
H2CO3
D.
CH3COOH
The forward reaction of this equilibrium is endothermic.
H2O (l)  H+ (aq) + OH− (aq)
What is correct about water at 50 °C?
A.
[H+] > [OH−]
B.
[H+] < [OH−]
C.
pH < 7.0
D.
pH = 7.0
Kw = 1.0 × 10−14 at 25 C
– 11 –
27.
28.
29.
30.
M15/4/CHEMI/HPM/ENG/TZ1/XX
Which equation represents a reaction for which a base dissociation constant expression, Kb, can
be written?
A.
CH3COOH (aq) + NH3 (aq)  CH3COO− (aq) + NH4+ (aq)
B.
HF (aq)  H+ (aq) + F− (aq)
C.
HCN (aq) + OH− (aq)  CN− (aq) + H2O (l)
D.
NH3 (aq) + H2O (l)  NH4+ (aq) + OH− (aq)
An equal amount of each of the following salts is added separately to the same volume of water.
Which salt will have the greatest effect on the pH of water?
A.
Al (NO3)3
B.
Na2SO4
C.
RbCl
D.
KBr
Which mixture will form a buffer in aqueous solution?
A.
0.10 mol NH3 + 0.20 mol HCl
B.
0.10 mol NH3 + 0.20 mol NaOH
C.
0.10 mol NaOH + 0.20 mol KCl
D.
0.20 mol NH3 + 0.10 mol HCl
Which represents a redox reaction?
A.
NaH (s) + H2O (l) → NaOH (aq) + H2 (g)
B.
CaCO3 (s) → CaO (s) + CO2 (g)
C.
CuCl2 (aq) + K2S (aq) → CuS (s) + 2KCl (aq)
D.
HCl (aq) + NH3 (aq) → NH4+Cl− (aq)
Turn over
– 12 –
31.
32.
Two half-cells are connected via a salt bridge to make a voltaic cell. Which statement about this
cell is correct?
A.
Oxidation occurs at the positive electrode (cathode).
B.
It is also known as an electrolytic cell.
C.
Ions flow through the salt bridge.
D.
It requires a power supply to operate.
Which signs are correct for a spontaneous redox reaction?
Standard electrode potential, E À
33.
M15/4/CHEMI/HPM/ENG/TZ1/XX
Standard free energy change, ∆G À
A.
+
−
B.
−
+
C.
−
−
D.
+
+
Consider the standard electrode potentials:
Fe2+ (aq) + 2e−  Fe (s)
E À = −0.45 V
Cl2 (g) + e−  Cl− (aq)
E À = +1.36 V
1
2
What is the standard cell potential, in V, for the reaction?
Cl2 (g) + Fe (s) → 2Cl− (aq) + Fe2+ (aq)
A.
+0.91
B.
+1.81
C.
+2.27
D.
+3.17
M15/4/CHEMI/HPM/ENG/TZ1/XX
– 13 –
34.
Applying IUPAC rules, what is the name of the compound?
CH3
CH3
CH
CH
C
CH3
CH2
CH3
35.
36.
A.
1-ethyl-1,3-dimethylbut-2-ene
B.
2-ethyl-4-methylpent-3-ene
C.
2-methyl-4-ethylpent-3-ene
D.
2,4-dimethylhex-2-ene
What is the product of the addition of chlorine, Cl2, to propene, C3H6?
A.
1,1-dichloropropane
B.
2,2-dichloropropane
C.
1,2-dichloropropane
D.
1,3-dichloropropane
What should be changed to alter the rate of nucleophilic substitution of tertiary halogenoalkanes?
A.
The nucleophile
B.
The concentration of the nucleophile
C.
The concentration of the tertiary halogenoalkane
D.
The size of the reaction flask
Turn over
– 14 –
37.
M15/4/CHEMI/HPM/ENG/TZ1/XX
Which compound could be X in the two-stage reaction pathway?
C2H6 → X → C2H5NH2
38.
A.
C2 H 4
B.
C2H5Cl
C.
C2H4Cl2
D.
C2H5OH
Which pair are geometric isomers?
A.
H
HO
H 3C
C
H
H
C
OH
H
and
O
C
O
H
C
C
OH
OH
B.
H 3C
Cl
H
C
H
C.
H 3C
C
H
C
H
CH 3
H 3C
C
H
H
C
and
H
CH 3
CH 3
H
C
C
H
and
C
Cl
Cl
H
H
D.
H
CH 3
H 3C
C
C
and
C
Cl
H
H 3C
H
C
CH 3
– 15 –
39.
40.
M15/4/CHEMI/HPM/ENG/TZ1/XX
Which reagent(s) can be used to convert CH3CH2CN to CH3CH2CH2NH2?
A.
H2 only
B.
H2O only
C.
H2 in the presence of Ni
D.
H2O in the presence of H+
A student weighs a standard 70.00 g mass five times using the same balance. Each time she
obtains a reading of 71.20 g. Which statement is correct about the precision and accuracy of the
measurements?
A.
Precise and accurate
B.
Precise but inaccurate
C.
Accurate but not precise
D.
Neither accurate nor precise
M15/4/CHEMI/HPM/ENG/TZ1/XX/M
Markscheme
May 2015
Chemistry
Higher level
Paper 1
2 pages
–2–
M15/4/CHEMI/HPM/ENG/TZ1/XX/M
1.
C
16.
D
31.
C
46.
–
2.
D
17.
C
32.
A
47.
–
3.
B
18.
B
33.
B
48.
–
4.
A
19.
A
34.
D
49.
–
5.
C
20.
B
35.
C
50.
–
6.
D
21.
B
36.
C
51.
–
7.
B
22.
D
37.
B
52.
–
8.
A
23.
A
38.
D
53.
–
9.
C
24.
A
39.
C
54.
–
10.
D
25.
B
40.
B
55.
–
11.
A
26.
C
41.
–
56.
–
12.
D
27.
D
42.
–
57.
–
13.
B
28.
A
43.
–
58.
–
14.
A
29.
D
44.
–
59.
–
15.
C
30.
A
45.
–
60.
–
m15/4/CHEMI/HPM/eng/TZ2/XX
Chemistry
Higher level
Paper 1
Thursday 14 May 2015 (afternoon)
1 hour
Instructions to candidates
• Do not open this examination paper until instructed to do so.
• Answer all the questions.
• For each question, choose the answer you consider to be the best and indicate your choice on
the answer sheet provided.
• The periodic table is provided for reference on page 2 of this examination paper.
• The maximum mark for this examination paper is [40 marks].
17 pages
2215 – 6113
© International Baccalaureate Organization 2015
39
Y
88.91
12
Mg
24.31
20
Ca
40.08
38
Sr
87.62
11
Na
22.99
19
K
39.10
37
Rb
85.47
40
Zr
91.22
22
Ti
47.90
41
Nb
92.91
23
V
50.94
87
Fr
(223)
88
Ra
(226)
‡
†
89 ‡
Ac
(227)
90
91
Th
Pa
232.04 231.04
58
59
Ce
Pr
140.12 140.91
26
Fe
55.85
27
Co
58.93
28
Ni
58.71
29
Cu
63.55
30
Zn
65.37
6
C
12.01
14
Si
28.09
32
Ge
72.59
13
Al
26.98
31
Ga
69.72
4
5
B
10.81
3
33
As
74.92
15
P
30.97
7
N
14.01
5
34
Se
78.96
16
S
32.06
8
O
16.00
6
10
Ne
20.18
18
Ar
39.95
36
Kr
83.80
17
Cl
35.45
35
Br
79.90
84
Po
(210)
85
At
(210)
93
Np
(237)
94
Pu
(242)
95
Am
(243)
96
Cm
(247)
97
Bk
(247)
98
Cf
(251)
99
Es
(254)
100
Fm
(257)
101
Md
(258)
102
No
(259)
103
Lr
(260)
66
61
68
64
67
62
69
65
63
70
71
60
Dy
Pm
Sm
Tm
Tb
Lu
Nd
Er
Gd
Ho
Eu
Yb
144.24 146.92 150.35 151.96 157.25 158.92 162.50 164.93 167.26 168.93 173.04 174.97
92
U
238.03
2
He
4.00
0
9
F
19.00
7
86
Rn
(222)
45
48
43
50
46
49
44
54
51
47
52
53
In
I
Rh
Cd
Tc
Sn
Pd
Ru
Xe
Sb
Ag
Te
98.91 101.07 102.91 106.42 107.87 112.40 114.82 118.69 121.75 127.60 126.90 131.30
25
Mn
54.94
The Periodic Table
80
75
82
78
81
76
83
79
77
74
Re
Pb
Pt
Tl
Os
Bi
Au
W
Ir
Hg
183.85 186.21 190.21 192.22 195.09 196.97 200.59 204.37 207.19 208.98
42
Mo
95.94
24
Cr
52.00
Relative atomic mass
Element
Atomic number
56
57 †
72
73
55
Ba
La
Ta
Cs
Hf
132.91 137.34 138.91 178.49 180.95
21
Sc
44.96
4
Be
9.01
2
3
Li
6.94
1
H
1.01
1
–2–
M15/4/CHEMI/HPM/ENG/TZ2/XX
–3–
1.
2.
M15/4/CHEMI/HPM/ENG/TZ2/XX
What is the total number of protons and electrons in one mole of hydrogen gas?
A.
2
B.
4
C.
1.2 × 1024
D.
2.4 × 1024
Which expression gives the sum of all the coefficients for the general equation for the complete
combustion of hydrocarbons?
___ CxHy (g) + ___ O2 (g) → ___ CO2 (g) + ___ H2O (l)
3.
4.
y
A.
1+ x +
B.
1+ x +
C.
1+ 2x +
3y
4
D.
1+ 2x +
3y
2
4
y
2
A gas with a molar mass (M) of 44 g mol–1 occupies a volume of 2.00 × 103 cm3 at a pressure of
1.01 × 105 Pa and a temperature of 25 °C. Which expression is correct for the calculation of the
mass of the gas, in g? (R = 8.31 J K–1 mol–1)
A.
44 × 1.01× 105 × 2.00 × 10 −3
8.31× 298
B.
44 × 1.01× 105 × 2.00 × 103
8.31× 25
C.
1.01× 105 × 2.00 × 10−3
44 × 8.31× 298
D.
44 × 1.01× 105 × 2.00 × 103
8.31× 298
Which ion will be deflected most in a mass spectrometer?
A.
16
O+
B.
16
O2+
C.
18
O+
D.
18
O2+
Turn over
–4–
5.
6.
7.
8.
M15/4/CHEMI/HPM/ENG/TZ2/XX
What is the electron configuration of the copper(I) ion, Cu+?
A.
1s22s22p63s23p64s13d9
B.
1s22s22p63s23p64s23d8
C.
1s22s22p63s23p64s13d10
D.
1s22s22p63s23p63d10
Which combination of properties best describes sodium oxide, Na2O?
Nature of bonding
Acidic or basic behaviour
A.
covalent
acidic
B.
ionic
basic
C.
covalent
basic
D.
ionic
acidic
What is the definition of electronegativity?
A.
The relative measure of the tendency of an atom when bonded in a molecule to attract a
shared pair of electrons towards itself.
B.
The minimum energy required to remove a mole of electrons from a mole of gaseous atoms.
C.
The enthalpy change occurring in kJ mol–1 when a gaseous atom gains one electron to form a
negative ion.
D.
The strength of an atom measured in kJ mol–1 to attract an electron to itself when bonded in a
molecule.
Which species cannot act as a ligand?
A.
NH4+
B.
H2 O
C.
Cl–
D.
OH–
M15/4/CHEMI/HPM/ENG/TZ2/XX
–5–
9.
10.
The formula of gallium phosphate is GaPO4. What is the correct formula of gallium sulfate?
A.
GaSO4
B.
GaS
C.
Ga2 (SO4)3
D.
Ga2S3
Which diagrams can be used to represent the Lewis (electron dot) structure of boron trifluoride?
I.
II.
F
F
X
B
F
11.
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
III.
X
F
F
B
X
F
X
X
X X
X
X
X X
F
BX X
F XX F XX
X X
X
X
X
X
X X
X X
Which correctly lists butane (Mr = 58), propanone (Mr = 58), propan-1-ol (Mr = 60) and propan-2-ol
(Mr = 60) in order of increasing boiling point?
A.
C4H10 < CH3COCH3 < CH3CH(OH)CH3 < CH3CH2CH2OH
B.
CH3CH2CH2OH < CH3CH(OH)CH3 < CH3COCH3 < C4H10
C.
C4H10 < CH3CH(OH)CH3 < CH3CH2CH2OH < CH3COCH3
D.
C4H10 < CH3COCH3 < CH3CH2CH2OH < CH3CH(OH)CH3
Turn over
–6–
12.
13.
M15/4/CHEMI/HPM/ENG/TZ2/XX
Which combination of shape and bond angle is correct for a molecule of xenon tetrafluoride, XeF4?
Shape
Bond angle
A.
square pyramid
90°
B.
square planar
90°
C.
tetrahedral
109.5°
D.
octahedral
90°
Which combination correctly describes the types of hybridization shown by the two carbon atoms
labelled α and β and the oxygen atom labelled γ in the molecule of paracetamol shown below?
H
α
H
O
γ
H
H
C
N
C
C
C
C
C
H
H
C
C β
O
H
H
Paracetamol
α
β
γ
A.
sp2
sp2
sp3
B.
sp3
sp2
sp2
C.
sp2
sp2
sp2
D.
sp2
sp3
sp3
H
–7–
14.
M15/4/CHEMI/HPM/ENG/TZ2/XX
When four moles of aluminium and four moles of iron combine with oxygen to form their oxides,
the enthalpy changes are –3338 kJ and –1644 kJ respectively.
4Al (s) + 3O2 (g) → 2Al2O3 (s)
∆H = –3338 kJ
4Fe (s) + 3O2 (g) → 2Fe2O3 (s)
∆H = –1644 kJ
What is the enthalpy change, in kJ, for the reduction of one mole of iron(III) oxide by aluminium?
Fe2O3 (s) + 2Al (s) → 2Fe (s) + Al2O3 (s)
15.
16.
A.
+1694
B.
+ 847
C.
– 847
D.
–1694
Which enthalpy changes can be calculated using only bond enthalpy data?
I.
N2 (g) + 3H2 (g) → 2NH3 (g)
II.
C2H5OH (l) + 3O2 (g) → 2CO2 (g) + 3H2O (g)
III.
CH4 (g) + Cl2 (g) → CH3Cl (g) + HCl (g)
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
Which equation represents the standard enthalpy change of formation, ΔHfÀ, of tetrachloromethane?
A.
C (g) + 4Cl (g) → CCl4 (g)
B.
C (s) + 4Cl (g) → CCl4 (l)
C.
C (g) + 2Cl2 (g) → CCl4 (g)
D.
C (s) + 2Cl2 (g) → CCl4 (l)
Turn over
–8–
17.
18.
M15/4/CHEMI/HPM/ENG/TZ2/XX
What is the correct order for increasing lattice enthalpy?
A.
MgO < MgCl2 < NaCl < CsCl
B.
CsCl < NaCl < MgCl2 < MgO
C.
NaCl < CsCl < MgO < MgCl2
D.
NaCl < CsCl < MgCl2 < MgO
Which combinations of values will result in a spontaneous reaction?
∆H / kJ mol–1
∆S / J K–1 mol–1
T/K
I.
– 100
– 100
300
II.
+ 100
– 100
300
III.
+ 100
+ 100
3000
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
–9–
100 cm3 of a 1.00 mol dm–3 solution of hydrochloric acid is added to 2.00 g of small pieces of
calcium carbonate at 20 °C. The volume of carbon dioxide produced against time is plotted to give
curve P.
Volume of CO2 (g) / cm3
19.
M15/4/CHEMI/HPM/ENG/TZ2/XX
Q
P
Time / s
Which change will produce curve Q, given that calcium carbonate is always the limiting reagent?
20.
A.
Increasing the volume of the hydrochloric acid to 200 cm3
B.
Increasing the mass of calcium carbonate to 4.00 g
C.
Increasing the concentration of the hydrochloric acid to 2.00 mol dm–3
D.
Replacing the 2.00 g of small pieces of calcium carbonate with 2.00 g of larger pieces of
calcium carbonate
What are the units of the rate constant for a zero-order reaction?
A.
s
B.
s–1
C.
mol–1 dm3 s–1
D.
mol dm–3 s–1
Turn over
– 10 –
21.
M15/4/CHEMI/HPM/ENG/TZ2/XX
The hydrolysis of tertiary bromoalkanes with a warm dilute aqueous sodium hydroxide solution
proceeds by a two-step SN1 mechanism.
Step I:
R – Br → R+ + Br–
Step II:
R+ + OH– → R – OH
Which description of this reaction is consistent with the above information?
22.
Step I
Step II
Rate expression
A.
fast
slow
rate = k [R – Br]
B.
slow
fast
rate = k [R – Br]
C.
fast
slow
rate = k [R – Br][OH–]
D.
slow
fast
rate = k [R – Br][OH–]
Which combination of temperature and pressure will give the greatest yield of sulfur trioxide?
2SO2 (g) + O2 (g)  2SO3 (g)
Temperature
Pressure
A.
high
low
B.
low
high
C.
high
high
D.
low
low
∆H = –196 kJ
– 11 –
23.
M15/4/CHEMI/HPM/ENG/TZ2/XX
The equation for the reaction between two gases, A and B, is:
2A (g) + 3B (g)  C (g) + 3D (g)
When the reaction is at equilibrium at 600 K the concentrations of A, B, C and D are 2, 1, 3 and
2 mol dm–3 respectively. What is the value of the equilibrium constant at 600 K?
24.
25.
A.
1
6
B.
9
7
C.
3
D.
6
Which species cannot function as a Lewis acid?
A.
BF3
B.
AlCl3
C.
CCl4
D.
H+
10.0 cm3 of a 1.00 × 10–2 mol dm–3 aqueous solution of sodium hydroxide is added to a volumetric
flask and the total volume is made up to 1.00 dm3 with distilled water. The resulting solution is then
thoroughly mixed.
What is the pH of the diluted solution?
A.
9
B.
10
C.
12
D.
14
Turn over
– 12 –
26.
M15/4/CHEMI/HPM/ENG/TZ2/XX
The strengths of four acids are:
glycine
chloroethanoic acid
phenol
butanoic acid
pKa = 9.87
Ka = 1.38 × 10–3
Ka = 1.00 × 10–10
pKa = 4.82
What is the order of increasing acid strength?
27.
28.
A.
chloroethanoic acid < butanoic acid < phenol < glycine
B.
glycine < phenol < chloroethanoic acid < butanoic acid
C.
phenol < chloroethanoic acid < butanoic acid < glycine
D.
phenol < glycine < butanoic acid < chloroethanoic acid
The pKa of ethanoic acid is 4.8 at 298 K. Which combination will produce a buffer solution with a
pH of 4.8 at 298 K?
A.
20.0 cm3 of 1.0 mol dm–3 CH3COOH and 10.0 cm3 of 1.0 mol dm–3 NaOH
B.
20.0 cm3 of 1.0 mol dm–3 CH3COOH and 20.0 cm3 of 1.0 mol dm–3 NaOH
C.
10.0 cm3 of 1.0 mol dm–3 CH3COOH and 20.0 cm3 of 1.0 mol dm–3 NaOH
D.
14.8 cm3 of 1.0 mol dm–3 CH3COOH and 10.0 cm3 of 1.0 mol dm–3 NaOH
Which compound forms an acidic solution when dissolved in water?
A.
FeCl3
B.
CH3NH2
C.
NaNO3
D.
Na2CO3
– 13 –
29.
30.
31.
M15/4/CHEMI/HPM/ENG/TZ2/XX
For which titration can the end point not be determined accurately by using an acid-base indicator?
A.
NH3 (aq) + CH3COOH (aq)
B.
NaOH (aq) + HNO3 (aq)
C.
NH3 (aq) + HNO3 (aq)
D.
NaOH (aq) + CH3COOH (aq)
Which is a redox reaction?
A.
[Cu (H2O)4]2+ (aq) + 4Cl– (aq) → [CuCl4]2– (aq) + 4H2O (l)
B.
Ag+ (aq) + Cl– (aq) → AgCl (s)
C.
Zn (s) + 2HCl (aq) → ZnCl2 (aq) + H2 (g)
D.
2K2CrO4 (aq) + 2HCl (aq) → K2Cr2O7 (aq) + H2O (l) + 2KCl (aq)
What is the coefficient for I– when the following equation is balanced using the smallest possible
whole numbers?
IO3– (aq) + ___ I– (aq) + ___ H+ (aq) → ___ I2 (aq) + ___ H2O (l)
A.
1
B.
2
C.
3
D.
5
Turn over
– 14 –
32.
M15/4/CHEMI/HPM/ENG/TZ2/XX
The standard electrode potentials for three reactions involving copper and copper ions are:
Cu2+ (aq) + e–  Cu+ (aq)
E À= + 0.15 V
Cu2+ (aq) + 2e–  Cu (s)
E À= + 0.34 V
Cu+ (aq) + e–  Cu (s)
E À= + 0.52 V
Which statement is correct?
33.
A.
Cu2+ ions are a better oxidizing agent than Cu+ ions.
B.
Copper metal is a better reducing agent than Cu+ ions.
C.
Cu+ ions will spontaneously form copper metal and Cu2+ ions in solution.
D.
Copper metal can be spontaneously oxidized by Cu2+ ions to form Cu+ ions.
The same quantity of electricity is passed through separate dilute aqueous solutions of sulfuric acid
and copper(II) sulfate using platinum electrodes under the same conditions. Which statement is
correct?
A.
The same volume of oxygen is obtained in both cases.
B.
The same volume of hydrogen is obtained in both cases.
C.
The amount of copper deposited at the negative electrode in the copper(II) sulfate solution is
half the amount of hydrogen gas formed at the negative electrode in the sulfuric acid solution.
D.
The pH of both solutions increases as the electrolysis proceeds.
M15/4/CHEMI/HPM/ENG/TZ2/XX
– 15 –
34.
Which of the following functional groups are present in aspirin?
O
H
C
C
H
C
C
H
O
O
C
C
H
C
C
O
H
H
C
H
H
Aspirin
35.
A.
Hydroxyl (alcohol) and ester
B.
Carboxyl (carboxylic acid) and ester
C.
Carboxyl (carboxylic acid) and carbonyl (ketone)
D.
Hydroxyl (alcohol) and carbonyl (ketone)
Which statements are correct for the reaction of ethene with bromine in the absence of
ultraviolet light?
I.
It is an addition reaction.
II.
The organic product is colourless.
III.
The organic product is saturated.
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
Turn over
– 16 –
36.
37.
38.
39.
M15/4/CHEMI/HPM/ENG/TZ2/XX
Applying IUPAC rules, what is the name of CH3CH (CH3)CONH2?
A.
Aminobutanone
B.
1-amino-2-methylpropanone
C.
2-methylpropanamide
D.
Butanamide
What is the correct order for the increasing rate of hydrolysis of halogenoalkanes by dilute
aqueous sodium hydroxide?
A.
CH3CH (CH3)CH2Cl < CH3CHClCH2CH3 < (CH3)3CCl < (CH3)3CBr
B.
(CH3)3CBr < (CH3)3CCl < CH3CHClCH2CH3 < CH3CH (CH3) CH2Cl
C.
(CH3)3CCl < (CH3)3CBr < CH3CHClCH2CH3 < CH3CH (CH3) CH2Cl
D.
CH3CHClCH2CH3 < CH3CH (CH3)CH2Cl < (CH3)3CBr < (CH3)3CCl
Which pairs of compounds can react together to undergo condensation polymerization reactions?
I.
HOOC – C6H4 – COOH and C2H5OH
II.
H2N – (CH2)6 – NH2 and HOOC – (CH2)4 – COOH
III.
H2N – CH2 – COOH and H2N – CH (CH3) – COOH
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
How many four-membered ring isomers are there of dichlorocyclobutane, C4H6Cl2?
A.
3
B.
4
C.
5
D.
6
– 17 –
40.
M15/4/CHEMI/HPM/ENG/TZ2/XX
What is the best way to minimize the random uncertainty when titrating an acid of unknown
strength against a standard solution of sodium hydroxide (ie one of known concentration)?
A.
First standardize the sodium hydroxide solution against a standard solution of a
different acid.
B.
Use a pH meter rather than an indicator to determine the equivalence point.
C.
Keep your eye at the same height as the meniscus when reading the burette.
D.
Repeat the titration several times.
M15/4/CHEMI/HPM/ENG/TZ2/XX/M
Markscheme
May 2015
Chemistry
Higher level
Paper 1
2 pages
–2–
M15/4/CHEMI/HPM/ENG/TZ2/XX/M
1.
D
16.
D
31.
D
46.
–
2.
C
17.
B
32.
C
47.
–
3.
A
18.
B
33.
A
48.
–
4.
B
19.
C
34.
B
49.
–
5.
D
20.
D
35.
D
50.
–
6.
B
21.
B
36.
C
51.
–
7.
A
22.
B
37.
A
52.
–
8.
A
23.
D
38.
C
53.
–
9.
C
24.
C
39.
C
54.
–
10.
C
25.
B
40.
D
55.
–
11.
A
26.
D
41.
–
56.
–
12.
B
27.
A
42.
–
57.
–
13.
A
28.
A
43.
–
58.
–
14.
C
29.
A
44.
–
59.
–
15.
B
30.
C
45.
–
60.
–
M15/4/CHEMI/HP2/ENG/TZ1/XX
Chemistry
Higher level
Paper 2
Thursday 14 May 2015 (afternoon)
Candidate session number
2 hours 15 minutes
Instructions to candidates








Write your session number in the boxes above.
Do not open this examination paper until instructed to do so.
Section A: answer all questions.
Section B: answer two questions.
Write your answers in the boxes provided.
A calculator is required for this paper.
A clean copy of the chemistry data booklet is required for this paper.
The maximum mark for this examination paper is [90 marks].
2215 – 6108
© International Baccalaureate Organization 2015
24 pages
24EP01
–2–
M15/4/CHEMI/HP2/ENG/TZ1/XX
Section A
Answer all questions. Write your answers in the boxes provided.
1.
Ethanedioic acid is a diprotic acid. A student determined the value of x in the formula of
hydrated ethanedioic acid, HOOC−COOH•xH2O, by titrating a known mass of the acid with
a 0.100 mol dm−3 solution of NaOH (aq).
0.795 g of ethanedioic acid was dissolved in distilled water and made up to a total volume of
250 cm3 in a volumetric flask.
25 cm3 of this ethanedioic acid solution was pipetted into a flask and titrated against aqueous
sodium hydroxide using phenolphthalein as an indicator.
The titration was then repeated twice to obtain the results below.
Volume of 0.100 mol dm–3 NaOH / cm3
Titration 1
Titration 2
Titration 3
Final burette reading (± 0.05)
13.00
25.70
38.20
Initial burette reading (± 0.05)
0.00
13.00
25.70
Volume added
(a)
Calculate the average volume of NaOH added, in cm3, in titrations 2 and 3, and then
calculate the amount, in mol, of NaOH added.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(This question continues on the following page)
24EP02
[2]
–3–
M15/4/CHEMI/HP2/ENG/TZ1/XX
(Question 1 continued)
(b)
(i)
The equation for the reaction taking place in the titration is:
HOOC−COOH (aq) + 2NaOH (aq) → NaOOC−COONa (aq) + 2H2O (l)
Determine the amount, in mol, of ethanedioic acid that reacts with the average
volume of NaOH (aq).
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Determine the amount, in mol, of ethanedioic acid present in 250 cm3 of
the original solution.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii)
Determine the molar mass of hydrated ethanedioic acid.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv)
Determine the value of x in the formula HOOC−COOH•xH2O.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (c)
Identify the strongest intermolecular force in solid ethanedioic acid.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(This question continues on the following page)
Turn over
24EP03
–4–
M15/4/CHEMI/HP2/ENG/TZ1/XX
(Question 1 continued)
(d)
Deduce the Lewis (electron dot) structure of ethanedioic acid, HOOC−COOH.
[1]
(e)
Predict and explain the difference in carbon-oxygen bond lengths in ethanedioic acid
and its conjugate base, −OOC−COO−.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
24EP04
–5–
2.
M15/4/CHEMI/HP2/ENG/TZ1/XX
This question is about the compounds of some period 3 elements.
(a)
State the equations for the reactions of sodium oxide with water and phosphorus(V)
oxide with water.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(b)
(i)
Explain why the melting point of phosphorus(V) oxide is lower than that of sodium
oxide in terms of their bonding and structure.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Predict whether phosphorus(V) oxide and sodium oxide conduct electricity in their
solid and molten states. Complete the boxes with “yes” or “no”.
[2]
Phosphorus(V) oxide
Sodium oxide
Solid state
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Molten state
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
24EP05
–6–
M15/4/CHEMI/HP2/ENG/TZ1/XX
(Question 2 continued)
(c)
Predict and explain the pH of the following aqueous solutions, using equations to
support your answer.
Ammonium chloride, NH4Cl (aq):
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Sodium methanoate, HCOONa (aq):
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
24EP06
[4]
–7–
3.
M15/4/CHEMI/HP2/ENG/TZ1/XX
The rate of reaction is an important factor in industrial processes such as the Contact
process to make sulfur trioxide, SO3 (g).
(a)
Define the term rate of reaction.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(b)
Describe the collision theory.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(c)
The Contact process involves this homogeneous equilibrium:
2SO2 (g) + O2(g)  2SO3 (g)
(i)
∆H = −198 kJ
State and explain how increasing the pressure of the reaction mixture affects the
yield of SO3.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
24EP07
–8–
M15/4/CHEMI/HP2/ENG/TZ1/XX
(Question 3 continued)
(ii)
2.00 mol of SO2 (g) are mixed with 3.00 mol of O2 (g) in a 1.00 dm3 container until
equilibrium is reached. At equilibrium there are 0.80 mol of SO3 (g).
Determine the equilibrium constant (Kc) assuming all gases are at the same
temperature and pressure.
[4]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii)
State the effect of increasing temperature on the value of Kc for this reaction.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (d)
Outline the economic importance of using a catalyst in the Contact process.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
24EP08
[2]
–9–
4.
M15/4/CHEMI/HP2/ENG/TZ1/XX
Copper is a metal that has been used by humans for thousands of years.
(a)
State the full electron configuration of 65Cu.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(b)
State one difference in the physical properties of the isotopes 63Cu and 65Cu and
explain why their chemical properties are the same.
[2]
Physical:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chemical:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(c)
Describe the bonding in solid copper.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Turn over
24EP09
– 10 –
M15/4/CHEMI/HP2/ENG/TZ1/XX
Section B
Answer two questions. Write your answers in the boxes provided.
5.
Ethanol has many industrial uses.
(a)
State an equation for the formation of ethanol from ethene and the necessary
reaction conditions.
[3]
Equation:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Conditions:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(b)
(i)
Define the term average bond enthalpy.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Ethanol can be used as a fuel. Determine the enthalpy of combustion of ethanol
at 298 K, in kJ mol−1, using the values in table 10 of the data booklet, assuming all
reactants and products are gaseous.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
24EP10
[4]
– 11 –
M15/4/CHEMI/HP2/ENG/TZ1/XX
(Question 5 continued)
(c)
Students can also measure the enthalpy of combustion of ethanol in the laboratory
using calorimetry. Suggest the major source of systematic error in these procedures.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(d)
State the equation for the acid-catalysed reaction of ethanol with propanoic acid and
state the name of the organic product.
[2]
Equation:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Name of the organic product:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(e)
(i)
A polyester can be formed when ethane-1,2-diol reacts with benzene-1,4dicarboxylic acid.
Deduce the structure of the repeating unit and state the other product formed.
[2]
Repeating unit:
Other product:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
24EP11
– 12 –
M15/4/CHEMI/HP2/ENG/TZ1/XX
(Question 5 continued)
(ii)
State the type of polymerization that occurs.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (f)
(i)
The standard enthalpy change of combustion, ∆H Àc , of propanoic acid is
−1527 kJ mol−1. Determine the standard enthalpy change of formation of
propanoic acid, in kJ mol−1, using this information and data from table 12 of the
data booklet.
[4]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Deduce, giving a reason, the sign of the standard entropy change of the system
for the formation of propanoic acid from its elements.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (g)
Identify three allotropes of carbon and describe their structures.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
24EP12
[4]
– 13 –
6.
M15/4/CHEMI/HP2/ENG/TZ1/XX
Bromomethane was used as a pesticide until it was found to be ozone-depleting.
(a)
State the equation for the reaction between methane and bromine to form bromomethane.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(b)
(i)
Explain, using equations, the complete free-radical mechanism for the reaction of
methane with bromine, including necessary reaction conditions.
[4]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Bromomethane reacts with aqueous sodium hydroxide. State the organic
product of this reaction.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (c)
Explain why the rate of the reaction between iodomethane, CH3I, and NaOH (aq) is
faster than the rate of the reaction between CH3Br and NaOH (aq).
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(This question continues on the following page)
Turn over
24EP13
– 14 –
M15/4/CHEMI/HP2/ENG/TZ1/XX
(Question 6 continued)
(d)
(i)
Bromine can be produced by the electrolysis of molten sodium bromide.
Deduce the half-equation for the reaction at each electrode.
[2]
Positive electrode (anode):
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Negative electrode (cathode):
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Predict the products formed at the electrodes during the electrolysis of
concentrated aqueous sodium bromide.
Positive electrode (anode):
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Negative electrode (cathode):
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
24EP14
[2]
– 15 –
M15/4/CHEMI/HP2/ENG/TZ1/XX
(Question 6 continued)
(e)
Bromine reacts with aqueous sodium iodide.
Br2 (aq) + 2NaI (aq) → I2 (aq) + 2NaBr (aq)
[1]
Identify the oxidizing agent in this reaction.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(f)
(i)
Define the term standard electrode potential, E À.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(ii)
Draw a labelled diagram for the voltaic cell in which the following reaction occurs.
Mg (s) + Cu2+ (aq) → Mg2+ (aq) + Cu (s)
Include in your answer the direction of electron flow and the polarity of
the electrodes.
[4]
(This question continues on the following page)
Turn over
24EP15
– 16 –
M15/4/CHEMI/HP2/ENG/TZ1/XX
(Question 6 continued)
(iii)
A student measures a voltage of 2.65 V in the voltaic cell formed between
magnesium and copper half-cells using a digital voltmeter.
State the random uncertainty of this value, in V, and the number of significant
figures in the answer.
[2]
Random uncertainty:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Significant figures:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv)
Outline how the student can reduce the random error in her results.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (g)
Determine the standard enthalpy change of formation, ∆H Àf , of NaCl (s), in kJ mol−1,
using a Born-Haber cycle and tables 7, 10 and 13 of the data booklet. The standard
enthalpy change of atomization (standard enthalpy change of sublimation), ∆H À
at , of
−1
Na (s) is +108 kJ mol .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
24EP16
[4]
– 17 –
7.
(a)
(i)
M15/4/CHEMI/HP2/ENG/TZ1/XX
Ethanol is a primary alcohol that can be oxidized by acidified potassium
dichromate(VI). Distinguish between the reaction conditions needed to produce
ethanal and ethanoic acid.
[2]
Ethanal:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ethanoic acid:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Determine the oxidation number of carbon in ethanol and ethanal.
[2]
Ethanol:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ethanal:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii)
Deduce the half-equation for the oxidation of ethanol to ethanal.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv)
Deduce the overall redox equation for the reaction of ethanol to ethanal with
acidified potassium dichromate(VI).
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
24EP17
– 18 –
M15/4/CHEMI/HP2/ENG/TZ1/XX
(Question 7 continued)
(b)
Ethanol can be made by reacting aqueous sodium hydroxide with bromoethane.
Explain the mechanism for this reaction, using curly arrows to represent the movement
of electron pairs.
(c)
(i)
[4]
Determine the orders of reaction of the reactants and the overall rate expression
for the reaction between 2-bromobutane and aqueous sodium hydroxide using
the data in the table.
Experiment
[NaOH] / mol dm−3
[C4H9Br] / mol dm−3
Rate / mol dm−3 s−1
1
1.00
1.00
1.66 × 10−3
2
0.50
1.00
8.31 × 10−4
3
0.25
0.25
1.02 × 10−4
4
1.00
0.50
8.29 × 10−4
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
24EP18
[2]
– 19 –
M15/4/CHEMI/HP2/ENG/TZ1/XX
(Question 7 continued)
(ii)
Determine the rate constant, k, with its units, using the data from experiment 3.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii)
Identify the molecularity of the rate-determining step in this reaction.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (d)
2-bromobutane exists as optical isomers.
(i)
State the essential feature of optical isomers.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Outline how a polarimeter can distinguish between these isomers.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (e)
Describe, using an equation, the elimination of HBr from 2-bromobutane, stating the
reagent used.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(This question continues on the following page)
Turn over
24EP19
– 20 –
M15/4/CHEMI/HP2/ENG/TZ1/XX
(Question 7 continued)
(f)
Describe the formation of σ and π bonds in an alkene.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(g)
The two most abundant isotopes of bromine have the mass numbers 79 and 81.
Calculate the relative abundance of 79Br using table 5 of the data booklet, assuming the
abundance of the other isotopes is negligible.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
24EP20
[2]
– 21 –
8.
M15/4/CHEMI/HP2/ENG/TZ1/XX
Acids can be described as strong or weak.
(a)
(i)
Outline the difference in dissociation between strong and weak acids of the same
concentration.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Describe three tests that can be carried out in the laboratory, and the expected
results, to distinguish between 0.10 mol dm−3 HCl (aq) and 0.10 mol dm−3
CH3COOH (aq).
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
Calculate the pH, using table 15 of the data booklet, of a solution of ethanoic acid
made by dissolving 1.40 g of the acid in distilled water to make a 500 cm3 solution.
[4]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(This question continues on the following page)
Turn over
24EP21
– 22 –
M15/4/CHEMI/HP2/ENG/TZ1/XX
(Question 8 continued)
(c)
(i)
Determine the pH at the equivalence point of the titration and the pKa of an
unknown acid using the acid-base titration curve below.
[3]
14
13
12
11
10
9
8
pH
7
6
5
4
3
2
1
0
0
2
4
6
8
10
12
14
16 18
20
22
24
3
Volume of NaOH / cm
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Identify, using table 16 of the data booklet, a suitable indicator to show the
end-point of this titration.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
24EP22
[1]
– 23 –
M15/4/CHEMI/HP2/ENG/TZ1/XX
(Question 8 continued)
(iii)
Describe how an indicator, that is a weak acid, works. Use Le Chatelier’s
principle in your answer.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (d)
(i)
[1]
State the formula of the conjugate base of chloroethanoic acid, CH2ClCOOH.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Identify, with a reason, whether chloroethanoic acid is weaker or stronger than
ethanoic acid using table 15 of the data booklet.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
24EP23
– 24 –
M15/4/CHEMI/HP2/ENG/TZ1/XX
(Question 8 continued)
(iii)
Determine the pH of the solution resulting when 100 cm3 of 0.50 mol dm−3
CH2ClCOOH is mixed with 200 cm3 of 0.10 mol dm−3 NaOH.
[4]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (e)
Describe how chlorine’s position in the periodic table is related to its electron
arrangement.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(f)
SCl2 and SClF5 are two sulfur chloride type compounds with sulfur having different
oxidation states. Predict the name of the shape, the bond angle and polarity of these
molecules.
Molecule
Shape
Bond angle
Polarity
SCl2
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SClF5
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24EP24
[3]
M15/4/CHEMI/HP2/ENG/TZ1/XX/M
Markscheme
May 2015
Chemistry
Higher level
Paper 2
15 pages
–2–
M15/4/CHEMI/HP2/ENG/TZ1/XX/M
This markscheme is the property of the International
Baccalaureate and must not be reproduced or distributed
to any other person without the authorization of the IB
Assessment Centre.
–3–
M15/4/CHEMI/HP2/ENG/TZ1/XX/M
Subject details: chemistry HL paper 2 markscheme
Mark allocation
Candidates are required to answer ALL questions in Section A [40 marks] and TWO questions in
Section B [2 x 25 marks]. Maximum total = [90 marks].
1.
A markscheme often has more marking points than the total allows. This is intentional.
2.
Each marking point has a separate line and the end is shown by means of a semicolon (;).
3.
An alternative answer or wording is indicated in the markscheme by a slash (/). Either wording can
be accepted.
4.
Words in brackets ( ) in the markscheme are not necessary to gain the mark.
5.
Words that are underlined are essential for the mark.
6.
The order of marking points does not have to be as in the markscheme, unless stated otherwise.
7.
If the candidate’s answer has the same “meaning” or can be clearly interpreted as being of
equivalent significance, detail and validity as that in the markscheme then award the mark.
Where this point is considered to be particularly relevant in a question it is emphasized by
OWTTE (or words to that effect).
8.
Remember that many candidates are writing in a second language. Effective communication is
more important than grammatical accuracy.
9.
Occasionally, a part of a question may require an answer that is required for subsequent
marking points. If an error is made in the first marking point then it should be penalized. However,
if the incorrect answer is used correctly in subsequent marking points then follow through marks
should be awarded. When marking, indicate this by adding ECF (error carried forward) on the
script.
10.
Do not penalize candidates for errors in units or significant figures, unless it is specifically referred
to in the markscheme.
11.
If a question specifically asks for the name of a substance, do not award a mark for a correct
formula unless directed otherwise in the markscheme. Similarly, if the formula is specifically asked
for, unless directed otherwise in the markscheme do not award a mark for a correct name.
12.
If a question asks for an equation for a reaction, a balanced symbol equation is usually expected,
do not award a mark for a word equation or an unbalanced equation unless directed otherwise in
the markscheme.
13.
Ignore missing or incorrect state symbols in an equation unless directed otherwise in the
markscheme.
–4–
M15/4/CHEMI/HP2/ENG/TZ1/XX/M
Section A
1.
(a)
(b)
 (12.70 + 12.50) 
=  12.60(cm3 ) ;

2


(0.01260 × 0.100 =)1.26 × 10−3 (mol) ;
Award [2] for correct final answer.
(i)
 1.26 × 10−3 
=  6.30 × 10 −4 (mol) ;

2


[1]
(ii)
(6.30 × 10 −4 × 10 = ) 6.30 × 10 −3 (mol) ;
[1]
(iii)
 0.795

−1
 6.30 × 10−3 =  126 (gmol ) ;


[1]
(iv)
(c)
(d)
Mr (C 2 H2O4 ) = 90.04 and Mr (H2O) = 18.02 ;
x = 2;
Accept integer values for Mr’s of 90 and 18 and any reasonable calculation.
Award [1 max] if no working shown.
hydrogen bonding;
O
O
XX
XX
;
H X O X C XX CX O X H
Mark cannot be scored if lone pairs are missing on oxygens.
Accept any combination of lines, dots or crosses to represent electron pairs.
(e)
[2]
[2]
[1]
[1]
Acid:
one double and one single bond / one shorter and one longer bond;
Accept “two double and two single”.
Conjugate base:
two 1.5 bonds / both bonds same length;
Accept “four / all”.
electrons delocalized / resonance forms;
Award marks for suitable diagrams.
[3]
–5–
2.
(a)
M15/4/CHEMI/HP2/ENG/TZ1/XX/M
Na2O(s) + H2O(l ) → 2NaOH(aq) ;
Accept Na2O(s) + H2O ( l ) → 2Na+ (aq) + 2OH −(aq) .
P4 O10 (s) + 6H2O (l ) → 4H3PO4 (aq) ;
[2]
Accept P2O5 (s) + 3H2O ( l ) → 2H3 PO4 (aq).
Accept P 4 O10 (s) + 6H2O( l ) → 4H + (aq) + 4H2 PO4− (aq) .
Ignore state symbols.
(b)
(i)
Na2O ionic and P4O10 covalent (within molecule);
Na2O in giant/3D/network/lattice structure with strong (ionic) bonds and
P4O10 has a (simple) molecular structure/weak intermolecular forces
(between molecules);
Award [1] for stating that bonds require more energy to break in Na2O than
in P4O10.
(ii)
Phosphorus(V) oxide
Sodium oxide
Solid state
no
no
Molten state
no
yes
[2]
;;
[2]
Award [2] for four correct.
Award [1] for two or three correct.
(c)
Ammonium chloride:
Accept any value in the range: 3 < pH < 7 ;
NH4 + (aq)  NH3 (aq) + H+ (aq) ;
Sodium methanoate:
7 < pH < 11;
HCOO− (aq) + H2O(l )  HCOOH(aq) + OH− (aq) ;
Award [1 max] for both M1 and M3 combined if stated “pH < 7/acidic for
ammonium chloride and pH > 7/alkaline/basic for sodium methanoate”.
Accept alternative suitable equations.
Award [1 max] for two correct explanations, such as “salt of weak acid and
strong base” or “salt of weak base and strong acid”, without equations.
Penalize missing equilibrium sign once only.
Ignore state symbols.
[4]
–6–
3.
(a)
(b)
M15/4/CHEMI/HP2/ENG/TZ1/XX/M
change in concentration of reactant/product with time / rate of change of
concentration;
Accept “increase” instead of “change” for product and “decrease” instead of
“change” for reactant.
Accept “mass/amount/volume” instead of “concentration”.
Do not accept substance.
collision frequency;
two particles must collide;
particles must have sufficient energy to overcome the activation energy/ E ≥ Ea ;
Concept of activation energy must be mentioned.
appropriate collision geometry/orientation;
(c)
[1]
(i)
(ii)
increases yield;
(equilibrium shifts to the right/products as) more gaseous moles in
reactants/on left / fewer gaseous moles in products/on right;
[3 max]
[2]
Eqm[O2 ] = 2.6 (mol dm−3 ) ;
Eqm[SO2 ] = 1.2(mol dm−3 ) ;
[SO3 ]2
;
[SO2 ]2 [O2 ]
K c = 0.17 ;
Award [4] for correct final answer.
Ignore units.
[4]
(K c ) decreases;
[1]
Kc =
(iii)
(d)
4.
catalyst increases rate of reaction / equilibrium reached faster / increases yield of
product per unit time;
reduces costs / reduces energy needed;
Do not accept just “increases the yield”.
(a)
1s22s22p63s23p63d104s1 / 1s22s22p63s23p64s13d10;
(b)
Physical:
63Cu lower boiling point/melting point/density/greater rate of diffusion than 65Cu;
Accept converse argument.
Do not accept “different mass”.
Chemical:
(properties identical because) same electron configuration/arrangement of
electrons;
Accept “same number of protons and electrons”.
Do not accept “same number of electrons” OR “same valence (electrons)” OR
“same atomic number” only.
(c)
electrostatic attraction;
between (a lattice of) cations/positive ions and delocalized/sea of electrons;
Do not award any mark for only stating “metallic bonding”.
[2]
[1]
[2]
[2]
–7–
M15/4/CHEMI/HP2/ENG/TZ1/XX/M
Section B
5.
(a)
Equation:
CH2CH2 + H2O → CH3 CH2OH / C2H4 + H2O → C2H5 OH ;
Conditions:
(concentrated) sulfuric acid/ H2 SO 4 ;
Do not accept dilute sulfuric acid.
Accept phosphoric acid/ H3 PO4 (on pellets of silicon dioxide) (for industrial
preparation).
heat / high temperature;
Do not accept warm.
Accept high pressure (for industrial preparation) for M3 only if H3 PO4 is
given for M2.
(b)
(i)
(ii)
energy needed to break (1 mol of) a bond in the gaseous state/phase;
(averaged over) similar compounds;
Do not accept “similar bonds” instead of “similar compounds”.
Concept of “similar” is important for M2.
[3]
[2]
CH3 CH2OH + 3O2 → 2CO2 + 3H2O ;
Bonds broken:
347 + (5 × 413) + 358 + 464 + (3 × 498) / 4728(kJ) /
C–C + 5C–H + C–O + O–H + 3O=O;
Bonds made:
(4 × 746) + (6 × 464) = 5768 (kJ) / 4C=O + 6O−H ;
ΔH = (4728 − 5768 = ) − 1040 (kJmol−1 ) / bonds broken − bonds formed;
Award [4] for correct final answer.
Award [3] for (+)1040 (kJ mol–1).
[4]
(c)
heat loss (to the surroundings);
[1]
(d)
CH3 CH2OH + CH3 CH2COOH  CH3CH2OOCCH2CH3 + H2O ;
ethyl propanoate;
Do not penalize if equilibrium arrow missing.
[2]
(e)
(i)
Repeating unit:
Continuation lines must be shown.
Ignore brackets and n.
Accept condensed formulas such as CH2 and C6H4.
(ii)
Other product:
H2O/water;
[2]
condensation;
[1]
–8–
(f)
(i)
M15/4/CHEMI/HP2/ENG/TZ1/XX/M
3C(s) + 3H2 (g) + O2 (g) → CH3 CH2COOH(l ) ;
ΔH Öf =  ΔH Öc (reactants) −  ΔH Öc (products) ;
Accept any suitable energy cycle.
 ΔH Öc (reactants) = 3 × ( −394) + 3 × (−286) / −2040 (kJ mol−1 ) ;
( ΔH Öf = [3 × ( −394) + 3 × ( −286)] − ( −1527) =) − 513 (kJ mol−1 ) ;
OR
CH3 CH2COOH(l ) + 3.5O2 (g) → 3CO2 (g) + 3H2O(g) ;
ΔH Öc =  ΔH Öf (products) −  ΔH Öf (reactants) ;
 ΔH
Ö
f
(products) = 3 × ( −394) + 3 × ( −286) / −2040 (kJ mol−1 ) ;
( ΔH Öf = [3 × ( −394) + 3 × ( −286)] − ( −1527) =) − 513 (kJ mol−1 ) ;
[4]
Ignore state symbols.
Award [4] for correct final answer.
(ii)
(g)
negative;
reduction in the number of gaseous molecules;
[2]
Allotropes:
Any three allotropes for [1] from:
diamond
graphite
fullerene
graphene;
Allow (carbon) nanotubes for graphene.
Accept C60 /C70 /buckminsterfullerene/bucky balls for fullerene.
Structures:
Any three for [3] from:
Diamond:
tetrahedral arrangement of (carbon) atoms/each carbon bonded to four others /
sp3 and 3D/covalent network structure;
Graphite:
each carbon bonded to three others (in a trigonal planar arrangement) / sp2 and
2D / layers of (carbon) atoms;
Fullerene:
each (carbon) atom bonded to three others (in a trigonal arrangement) / sp2 and
joined in a ball/cage/sphere/connected hexagons and pentagons;
Accept “trigonal planar” for “each carbon atom bonded to three others” part in M4.
Graphene:
each carbon bonded to three others (in a trigonal arrangement) / sp2 and
2D structure;
[4]
–9–
6.
(a)
CH4 + Br2 → CH3Br + HBr ;
(b)
(i)
M15/4/CHEMI/HP2/ENG/TZ1/XX/M
[1]
Initiation:
UV/hf /hυ
Br2 → 2Br  ;
Reference to UV/light or high temperatures must be included.
Propagation:
Br  + CH4 → CH3  + HBr ;
CH3  + Br2 → CH3Br + Br  ;
Termination:
Award [1 max] for any one of:
Br  + Br  → Br2 ;
CH3  + Br  → CH3Br ;
CH3  + CH3  → C2H6 ;
Allow representation of radical without  (eg Br, CH3) if consistent throughout
mechanism.
Award [3 max] if initiation, propagation and termination are not stated or are
incorrectly labelled for equations.
(ii)
(c)
(d)
methanol/CH3OH;
[1]
C–I bond is weaker than the C–Br bond so more easily broken;
C–I bond is longer than the C–Br bond / I larger than Br so bonding electrons not
as tightly held / I– is better leaving group than Br–;
(i)
[4 max]
[2]
Positive electrode (anode):
2Br – → Br2 (g) + 2e− / Br − →
1
Br2 (g) + e− ;
2
Negative electrode (cathode):
Na+ + e− → Na (l ) ;
[2]
Award [1 max] for correct equations at incorrect electrodes.
Ignore state symbols.
Accept e instead of e–.
Penalize use of equilibrium signs once only.
(ii)
Positive electrode (anode):
bromine/Br2;
Negative electrode (cathode):
hydrogen/H2;
Allow sodium hydroxide/NaOH/hydroxide/ OH − formation.
[2]
– 10 –
(e)
bromine/Br2;
Do not accept bromide/ Br − .
(f)
(i)
M15/4/CHEMI/HP2/ENG/TZ1/XX/M
[1]
potential of reduction half-reaction under standard conditions measured
relative to standard hydrogen electrode/SHE / potential under standard
conditions relative to standard hydrogen electrode/SHE;
Instead of standard state allow either solute concentration of 1 mol dm–3 or
100 kPa/1.00 × 105 Pa for gases.
Allow 1 bar for 100 kPa/1.00 × 105 Pa.
Allow 1 atm.
Allow voltage instead of potential.
[1]
(ii)
direction of electron flow
Mg (s)
Cu (s)
Mg2+ (aq)
Cu2+ (aq)
correct diagram including (voltmeter), 4 correct species (state symbols not
required) and connecting wires;
No credit if wires to electrodes immersed in the solutions.
Accept ammeter/meter/lamp instead of voltmeter.
labelled salt bridge;
Accept an appropriate salt (name or formula) instead of salt bridge
(eg, potassium nitrate).
(iii)
(iv)
correctly labelled electrodes as +/cathode and −/anode;
flow of electrons from Mg to Cu in external circuit;
[4]
Random uncertainty: (±) 0.01 (V);
Significant figures: 3;
[2]
repeat readings and take an average / use more precise equipment;
[1]
– 11 –
(g)
M15/4/CHEMI/HP2/ENG/TZ1/XX/M
1
1
bond enthalpy / 243 / 121.5 (kJ mol−1);
2
2
correct values for ionization Na (+496 kJ mol−1) and electron affinity Cl (−349 kJ mol−1)
and lattice enthalpy of NaCl (+790 kJ mol−1 / +769 kJ mol−1);
Born-Haber energy cycle;
Accept lines or arrows in energy cycle.
atomization of chlorine =
ΔH Öf (NaCl (s)) = −413.5 / −413 / −414(kJ mol−1 ) ;
[4]
Accept −392.5 / −392 / −393 if +769 used for lattice enthalpy.
Award [4] for correct final answer.
7.
(a)
(i)
(ii)
(iii)
Ethanal: distill off product as it forms;
Accept distillation.
Ethanoic acid: (heat under) reflux / use excess oxidizing agent;
[2]
Ethanol: –2/–II;
Ethanal: –1/–I;
Do not accept 2–, 1– but penalize once only.
[2]
CH3 CH2OH → CH3 CHO + 2H+ + 2e − ;
[1]
Half-equation required. Do not accept C2 H5OH + 2[O] → CH3CHO + H2O .
Accept e for e−.
(iv)
3CH3 CH2OH(aq) + Cr2O7 2− (aq) + 8H+ (aq) → 2Cr 3 + (aq) + 3CH3CHO(l ) + 7H2O(l)
correct reactants and products;
correct balancing;
M2 can only be scored if M1 correct.
Ignore state symbols.
[2]
– 12 –
M15/4/CHEMI/HP2/ENG/TZ1/XX/M
(b)
curly arrow going from lone pair/negative charge on O in HO– to C;
Do not allow curly arrow originating on H in HO–.
curly arrow showing Br leaving;
Accept curly arrow either going from bond between C and Br to Br in
bromoethane or in the transition state.
representation of transition state showing negative charge, square brackets and
partial bonds;
Do not penalize if HO and Br are not at 180° to each other.
Do not award M3 if OH----C bond is represented.
formation of organic product CH3CH2OH and Br–;
Award [3 max] for correct SN1 mechanism.
(c)
(i)
[NaOH] / [OH− ] is 1/first order and [C4H9Br] is 1/first order;
rate = k [OH− ][C4H9Br] / rate = k [NaOH][C4H9Br] ;
Square brackets must be used for M2.
(ii)
(d)

=  0.0016 / 1.6 × 10−3 ;

−1
3 −1
mol dm s ;
Accept M–1 s–1.
Ignore order of units.
Must use experiment 3 data.
[2]
 1.02 × 10−4

 0.25 × 0.25
[2]
(iii)
bimolecular/2;
Accept dimolecular.
(i)
chiral/asymmetric carbon / carbon attached to 4 different groups / nonsuper imposable mirror images;
[1]
enantiomers rotate plane of (plane-) polarized light;
in opposite directions (by equal amounts);
[2]
(ii)
(e)
[4]
[1]
CH3 CHBrCH2CH3 + OH− → CH3 CHCHCH3 + H2O + Br − /
CH3 CHBrCH2CH3 + OH− → CH2CHCH2CH3 + H2O + Br − /
CH3 CHBrCH2CH3 + CH3 CH2O − → CH3 CHCHCH3 + CH3 CH2OH + Br − ;
Accept equations with NaOH.
alcoholic sodium hydroxide / ethanolic OH–;
[2]
– 13 –
(f)
M15/4/CHEMI/HP2/ENG/TZ1/XX/M
Sigma bonds:
result from head-on/end-on overlap of orbitals / OWTTE;
Accept axial overlap of orbitals.
Accept “symmetric orbital” with respect to same plane / OWTTE.
Pi bonds:
/
result from sideways overlap of orbitals / OWTTE;
Accept “antisymmetric orbitals” with respect to (defining) plane (containing at
least one atom) / OWTTE.
(g)
8.
(a)
79.91 = 79 x + 81(1 − x ) ;
Award M1 for any suitable calculation.
(abundance 79Br =) 54.5 %;
Award [2] for correct final answer.
(i)
(ii)
weak acids dissociate only partially and strong acids (are assumed to)
dissociate fully;
[2]
[2]
[1]
measuring electrical conductivity and strong acids have greater electrical
conductivity/weak acids have lower electrical conductivity;
Do not accept conductivity for electrical conductivity.
Accept explanation in terms of lightbulb in circuit.
measure pH/use universal indicator and pH higher for weak acid/pH lower
for strong acid;
conduct titration with a strong base and equivalence point higher for weak
acid / buffer region for weak acid;
adding a reactive metal/carbonate/hydrogen carbonate and stronger
effervescence/faster reaction with strong acids;
Accept converse argument.
Accept correct example.
adding a strong base and strong acid would increase more in temperature/
weak acids increase less in temperature;
Accept correct example.
Award [1 max] for three suitable tests without correct results.
Accept specific examples with given strong acid and weak acid.
Accept “addition of AgNO3 (aq) and white precipitate with HCl (aq)”.
Do not accept “smell”.
[3 max]
– 14 –
(b)
M15/4/CHEMI/HP2/ENG/TZ1/XX/M
0.0233
1.40
= 0.0233 (mol) and
= 0.0466 (mol dm−3 ) ;
0.500
60.06
(pK a = 4.76) K a = 1.7 × 10−5 ;
[H+ ] = K a [HA] = 8.9 × 10−4 ;
Accept 9.0 ×10 −4 .
pH = 3.05 ;
Award [4] for correct final answer.
Accept alternative methods.
(c)
(i)
[4]
Equivalence point: pH of 9.5;
Accept values between 9 and 10.
pK a = pH at half equivalence point;
(d)
pK a = 5.4;
Accept any value between 5.2 and 5.6.
Award [2] for M2 and M3 if correct pKa given without explanation.
[3]
(ii)
phenolphthalein;
[1]
(iii)
HIn (aq)  H+ (aq) + In– (aq) and HIn and In– have different colours;
Ignore state symbols.
equilibrium shifts depending on addition of H+ and OH– / more HIn in
acid/low pH / more In– in alkali/high pH;
[2]
(i)
CH2ClCOO–;
[1]
(ii)
stronger because pKa of chloroethanoic acid is < pKa of ethanoic acid;
[1]
0.030
= 0.10 (mol dm−3 ) ;
0.300
0.020
= 0.067(mol dm−3 ) ;
Concentration of base/salt:
0.300
K × [HA] 1.3 × 10−3 × 0.10
[H+ ] = a −
/
/ 1.9 × 10−3 (mol dm−3 ) ;
0.067
[A ]
pH = 2.72 ;
Award [4] for correct final answer.
Accept 2.69, 2.70 or 2.7.
Alternative for M3 and M4 if Henderson-Hasselbalch equation used:
[base]
 0.067 
/ 2.87 + log 
M3: pH = pKa + log

[acid]
 0.10 
M4: pH = 2.70 .
[4]
(iii)
Concentration of acid:
Award [1 max] for nacid ( = 100 × 0.50 ÷ 1000) = 0.050 mol and
nbase ( = 200 × 0.10 ÷ 1000) = 0.020 mol .
– 15 –
(e)
M15/4/CHEMI/HP2/ENG/TZ1/XX/M
Cl has 7 valence electrons and is in group 7;
Accept “group 17” as suggested by IUPAC.
Cl has 3 occupied (electron) shells/energy levels and so is in period 3;
(f)
Molecule
Shape
SCl2
bent/angular/
v-shaped
SClF5
Octahedral
Accept square
bipyramidal.
Bond angle
< 109.5°
Accept 100° − 108°.
Literature value is 103°.
90° (180°)
[2]
Polarity
polar
polar
Do not accept ECF for bond angles and polarities from incorrect shapes.
Award [3] for all six correct.
Award [2] for four or five correct.
Award [1] for two or three correct.
;;;
[3]
M15/4/CHEMI/HP2/ENG/TZ2/XX
Chemistry
Higher level
Paper 2
Thursday 14 May 2015 (afternoon)
Candidate session number
2 hours 15 minutes
Instructions to candidates








Write your session number in the boxes above.
Do not open this examination paper until instructed to do so.
Section A: answer all questions.
Section B: answer two questions.
Write your answers in the boxes provided.
A calculator is required for this paper.
A clean copy of the chemistry data booklet is required for this paper.
The maximum mark for this examination paper is [90 marks].
2215 – 6114
© International Baccalaureate Organization 2015
28 pages
28EP01
–2–
M15/4/CHEMI/HP2/ENG/TZ2/XX
Section A
Answer all questions. Write your answers in the boxes provided.
1.
A student carried out an experiment to determine the concentration of a hydrochloric acid
solution and the enthalpy change of the reaction between aqueous sodium hydroxide and
this acid by thermometric titration.
She added 5.0 cm3 portions of hydrochloric acid to 25.0 cm3 of 1.00 mol dm–3 sodium
hydroxide solution in a glass beaker until the total volume of acid added was 50.0 cm3,
measuring the temperature of the mixture each time. Her results are plotted in the
graph below.
32
31
Temperature / °C
30
29
28
27
26
25
24
0.0
10.0
20.0
30.0
40.0
Volume of hydrochloric acid added / cm
50.0
3
The initial temperature of both solutions was the same.
(a)
(i)
By drawing appropriate lines, determine the volume of hydrochloric acid required
to completely neutralize the 25.0 cm3 of sodium hydroxide solution.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
28EP02
[2]
–3–
M15/4/CHEMI/HP2/ENG/TZ2/XX
(Question 1 continued)
(ii)
Determine the concentration of the hydrochloric acid, including units.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
(i)
Determine the change in temperature, ΔT.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Calculate the enthalpy change, in kJ mol–1, for the reaction of hydrochloric acid
and sodium hydroxide solution.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii)
The accepted theoretical value from the literature of this enthalpy change is
–58 kJ mol–1. Calculate the percentage error correct to two significant figures.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
28EP03
–4–
M15/4/CHEMI/HP2/ENG/TZ2/XX
(Question 1 continued)
(iv)
Suggest the major source of error in the experimental procedure and an
improvement that could be made to reduce it.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28EP04
[2]
–5–
2.
(a)
M15/4/CHEMI/HP2/ENG/TZ2/XX
Define the term rate of reaction.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(b)
Explain why increasing the particle size of a solid reactant decreases the rate
of reaction.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(c)
Nitrogen(II) oxide reacts with hydrogen according to the equation below.
2NO (g) + 2H2 (g) → N2 (g) + 2H2O (g)
A suggested mechanism for this reaction is:
(i)
Step 1:
NO + H2  X
fast
Step 2:
X + NO → Y + H2O
slow
Step 3:
Y + H2 → N2 + H2O
fast
Identify the rate-determining step.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
A student hypothesized that the order of reaction with respect to H2 is 2.
Evaluate this hypothesis.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
28EP05
–6–
3.
M15/4/CHEMI/HP2/ENG/TZ2/XX
Carbon monoxide reacts with hydrogen to produce methanol.
CO (g) + 2H2 (g) → CH3OH (l)
ΔH Àf / kJ mol–1
ΔG Àf / kJ mol–1
S À / J mol–1 K–1
CO (g)
– 110.5
– 137.2
+ 197.6
CH3OH (l)
– 239.0
– 166.0
+ 126.8
Substance
(a)
Calculate the standard enthalpy change, ΔH À, in kJ mol–1, for the reaction.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(b)
Calculate the standard free energy change, ΔG À, in kJ mol–1, for the reaction
(ΔG Àf (H2) = 0 kJ mol–1).
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(c)
Using the values obtained in parts (a) and (b), calculate the standard entropy change,
ΔS À, in J mol–1 K–1, for the reaction at 298 K.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(d)
Determine the absolute entropy, S À, in J mol–1 K–1, for H2 (g) at 298 K.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
28EP06
[2]
–7–
4.
M15/4/CHEMI/HP2/ENG/TZ2/XX
A buffer solution with a pH of 3.87 contains 7.41 g dm–3 of propanoic acid, CH3CH2COOH,
together with an unknown quantity of sodium propanoate, CH3CH2COONa.
(a)
Define the term buffer solution.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(b)
Explain, using appropriate equations, how this solution acts as a buffer solution.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(c)
Calculate the concentration, in mol dm–3, of sodium propanoate in this buffer solution.
The pKa of propanoic acid is 4.87 at 298 K.
[4]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Turn over
28EP07
5.
(a)
–8–
M15/4/CHEMI/HP2/ENG/TZ2/XX
State two features of a homologous series.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(b)
Ethane, a member of the homologous series of alkanes, can react with bromine.
Explain the free-radical mechanism of this reaction, including any necessary reaction
conditions.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
28EP08
[4]
–9–
6.
M15/4/CHEMI/HP2/ENG/TZ2/XX
Electrolysis is an important industrial process used to obtain very reactive elements from
their common ores.
(a)
Molten magnesium chloride can be electrolysed using inert graphite electrodes
at 800 °C.
Deduce the half-equations, including state symbols, for the reactions occurring at
each electrode. (The melting points of MgCl2 and Mg are 714 °C and 649 °C
respectively.)
[3]
Positive electrode (anode):
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Negative electrode (cathode):
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(b)
Aluminium can also be obtained by electrolysis. Suggest one reason why aluminium is
often used instead of iron by engineers.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Turn over
28EP09
– 10 –
M15/4/CHEMI/HP2/ENG/TZ2/XX
Section B
Answer two questions. Write your answers in the boxes provided.
7.
When nitrogen gas and hydrogen gas are allowed to react in a closed container the following
equilibrium is established.
N2 (g) + 3H2 (g)  2NH3 (g)
(a)
(i)
ΔH = –92.6 kJ
Outline two characteristics of a reversible reaction in a state of
dynamic equilibrium.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Predict, with a reason, how each of the following changes affects the position
of equilibrium.
[2]
The volume of the container is increased.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ammonia is removed from the equilibrium mixture.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii)
Define the term activation energy, Ea.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
28EP10
[1]
– 11 –
M15/4/CHEMI/HP2/ENG/TZ2/XX
(Question 7 continued)
(b)
Ammonia is manufactured by the Haber process in which iron is used as a catalyst.
Explain the effect of a catalyst on the rate of reaction.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(c)
Typical conditions used in the Haber process are 500 °C and 200 atm, resulting in
approximately 15 % yield of ammonia.
(i)
Explain why a temperature lower than 500 °C is not used.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Outline why a pressure higher than 200 atm is not often used.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
28EP11
– 12 –
M15/4/CHEMI/HP2/ENG/TZ2/XX
(Question 7 continued)
(d)
(i)
Deduce the equilibrium constant expression, Kc, for the reaction on page 10.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
When 1.00 mol of nitrogen and 3.00 mol of hydrogen were allowed to reach
equilibrium in a 1.00 dm3 container at a temperature of 500 °C and a pressure of
1000 atm, the equilibrium mixture contained 1.46 mol of ammonia.
Calculate the value of Kc at 500 °C.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (e)
(i)
Define the term base according to the Lewis theory.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Define the term weak base according to the Brønsted–Lowry theory.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
28EP12
[1]
– 13 –
M15/4/CHEMI/HP2/ENG/TZ2/XX
(Question 7 continued)
(iii)
Deduce the formulas of conjugate acid-base pairs in the reaction below.
CH3NH2 (aq) + H2O (l)  CH3NH3+ (aq) + OH− (aq)
(f)
[2]
Acid
Conjugate base
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Determine the pH of a 0.100 mol dm−3 solution of ammonia, NH3 (aq), using
tables 2 and 15 of the data booklet.
[4]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(This question continues on the following page)
Turn over
28EP13
– 14 –
M15/4/CHEMI/HP2/ENG/TZ2/XX
(Question 7 continued)
(g)
(i)
Sketch the pH titration curve obtained when 50.0 cm3 of 0.100 mol dm–3 NH3 (aq) is
added to 25.0 cm3 of 0.100 mol dm–3 HCl (aq).
[3]
12
7
pH
0
0
5
10
15
20
25
30
35
40
45
50
NH3 (aq) volume / cm3
(ii)
Identify an indicator from table 16 of the data booklet that could be used
for this titration.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28EP14
[1]
– 15 –
8.
M15/4/CHEMI/HP2/ENG/TZ2/XX
Chromium is a transition metal with many uses.
(a)
(i)
Draw an orbital diagram (using the arrow-in-box notation) showing the electrons
in the 4s and 3d sub-levels in chromium metal.
[1]
(ii)
Outline the nature of the metallic bonding present in chromium.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii)
Explain why chromium metal is malleable.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
(i)
State the name of Cr2O3.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Describe the ionic bonding present in Cr2O3 and how the ions are formed.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
28EP15
– 16 –
M15/4/CHEMI/HP2/ENG/TZ2/XX
(Question 8 continued)
(iii)
Suggest why solid Cr2O3 does not conduct electricity.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (c)
Chromium forms the complex ion [Cr (NH3)4Cl2]+.
(i)
Deduce the oxidation number of chromium in this complex.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Describe the nature of the ligand-chromium ion bonds in terms of acid-base
theory.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii)
Explain why [Cr (NH3)4Cl2]+ is coloured.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
28EP16
[4]
– 17 –
M15/4/CHEMI/HP2/ENG/TZ2/XX
(Question 8 continued)
(d)
(iv)
Draw the structures of two possible isomers of this complex ion.
[2]
(i)
The dichromate ion, Cr2O72– (aq), and the iodide ion, I– (aq), react together in the
presence of an acid to form Cr3+ (aq) and IO3– (aq) ions. Deduce the half-equation
for the reaction of I– to IO3– and the overall equation for this reaction.
[2]
Half-equation:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Overall equation:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Explain in terms of oxidation numbers whether iodine is oxidized or reduced
in part (d) (i).
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
28EP17
– 18 –
M15/4/CHEMI/HP2/ENG/TZ2/XX
(Question 8 continued)
(e)
A voltaic cell is constructed as follows. One half-cell contains a chromium electrode
immersed in a solution containing Cr3+ (aq) ions. The other half-cell contains a copper
electrode immersed in a solution containing Cu2+ (aq) ions. The two electrodes are
connected to a voltmeter and the two solutions by a salt bridge.
Voltmeter
V
Salt bridge
Cu (s)
Cr (s)
Cr3+ (aq)
(i)
Cu2+ (aq)
Define the term standard electrode potential.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Calculate the cell potential, in V, under standard conditions, for this voltaic cell,
using table 14 of the data booklet and EÀCr3+/Cr = – 0.74 V.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
28EP18
[1]
– 19 –
M15/4/CHEMI/HP2/ENG/TZ2/XX
(Question 8 continued)
(iii)
Predict the balanced equation for the spontaneous reaction which will produce a
current in this voltaic cell.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv)
Identify the negative and the positive electrodes in this cell.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (v)
Predict the direction of movement of electrons in the external circuit.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (vi)
State the directions in which the negative ions (anions) and the positive ions
(cations) flow in the salt bridge.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
28EP19
– 20 –
9.
(a)
M15/4/CHEMI/HP2/ENG/TZ2/XX
Consider the structure and bonding in MgCl2 and PCl3.
(i)
State and explain the electrical conductivities of these two chloride compounds in
their liquid state.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Suggest, giving your reasons, the approximate pH values of the solutions formed
by adding each chloride compound separately to distilled water.
[4]
MgCl2 :
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PCl3 :
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
(i)
Identify the acid-base character of the oxides of each of the elements from
sodium to chlorine in period 3.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
28EP20
[2]
– 21 –
M15/4/CHEMI/HP2/ENG/TZ2/XX
(Question 9 continued)
(ii)
State the equations for the separate reactions of sodium oxide and phosphorus(V)
oxide with water.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (c)
Consider the molecules PBr3 and SF4.
(i)
Deduce the Lewis (electron dot) structure of both molecules.
[2]
(ii)
Predict the shapes of the two molecules, giving the Br–P–Br bond angle in PBr3
and the F–S–F bond angles in SF4.
[4]
PBr3
SF4
Shape:
Shape:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Bond angle:
Bond angles:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(This question continues on the following page)
Turn over
28EP21
– 22 –
M15/4/CHEMI/HP2/ENG/TZ2/XX
(Question 9 continued)
(iii)
Explain why both PBr3 and SF4 are polar.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (d)
The structure of cis-but-2-ene-1,4-dioic acid is shown below.
O
β
H
C
O
H
C
H
O
α
C
C
H
O
(i)
Describe the covalent bond between carbon and hydrogen in the molecule above
and how it is formed.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
28EP22
[2]
– 23 –
M15/4/CHEMI/HP2/ENG/TZ2/XX
(Question 9 continued)
(ii)
[1]
Deduce the hybridization of the oxygen atoms labelled α and β.
α:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . β:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii)
Describe sigma (σ) and pi (π) bonds between atoms.
[2]
σ bond:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . π bond:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv)
Identify the number of sigma (σ) and pi (π) bonds present in a molecule of
cis-but-2-ene-1,4-dioic acid.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
28EP23
– 24 –
10.
M15/4/CHEMI/HP2/ENG/TZ2/XX
Some reactions of but-2-ene are given below.
Poly(but-2-ene)
Compound A
Br2(l)
in the absence
of UV
H 3C
CH
CH
But-2-ene
CH3
concentrated H2SO4
H2O(l)
C4H9OH
Compound C
HBr
H 3C
CHBr
CH2
CH3
Compound B
(a)
(i)
Deduce the full structural formula of compound A.
[1]
(ii)
Apply IUPAC rules to name compound A.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii)
Describe the colour change observed when excess but-2-ene reacts with bromine
to form compound A.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
28EP24
[1]
– 25 –
M15/4/CHEMI/HP2/ENG/TZ2/XX
(Question 10 continued)
(b)
(i)
Outline two reasons why the polymerization of alkenes is of economic importance.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (c)
(ii)
Identify the structure of the repeating unit of poly(but-2-ene).
[1]
(i)
Compound C, C4H9OH, can also be formed by reacting compound B,
CH3CHBrCH2CH3, with aqueous potassium hydroxide. This reaction proceeds by
both SN1 and SN2 mechanisms. Explain the SN2 mechanism, using curly arrows
to represent the movement of electron pairs.
[4]
(This question continues on the following page)
Turn over
28EP25
– 26 –
M15/4/CHEMI/HP2/ENG/TZ2/XX
(Question 10 continued)
(ii)
Explain why the hydroxide ion is a better nucleophile than water.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (d)
(i)
Compound B, CH3CHBrCH2CH3, also reacts with potassium cyanide.
Apply IUPAC rules to name the organic product formed.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
The organic product of the reaction in part (d) (i) can be reduced to:
H
H
H
CH3 H
H
C
C
C
C
N
H
H
H
H
H
State the two reagents required.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii)
Deduce the full structural formula of the organic product formed when the
compound in part (d) (ii) reacts with ethanoic acid in the presence of an acid
catalyst.
(This question continues on the following page)
28EP26
[1]
– 27 –
M15/4/CHEMI/HP2/ENG/TZ2/XX
(Question 10 continued)
(e)
Compound C, C4H9OH, can be oxidized by acidified potassium dichromate(VI) to form
compound F.
(i)
State the name of the functional group present in compound F.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (f)
(ii)
Deduce the structural formula of an alcohol which is a structural isomer of
compound C and cannot be oxidized by acidified potassium dichromate(VI).
[1]
Explain why but-2-ene is more volatile than compound C.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(g)
Deduce the equation for the complete combustion of compound C.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(This question continues on the following page)
Turn over
28EP27
– 28 –
M15/4/CHEMI/HP2/ENG/TZ2/XX
(Question 10 continued)
(h)
But-2-ene can exist as two geometrical isomers. Geometrical isomerism is a form
of stereoisomerism.
(i)
Define the term stereoisomers.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
State the conditions needed for a compound to show geometrical isomerism.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii)
Draw the structures of the two geometrical isomers of but-2-ene, clearly
identifying each as cis or trans.
28EP28
[2]
M15/4/CHEMI/HP2/ENG/TZ2/XX/M
Markscheme
May 2015
Chemistry
Higher level
Paper 2
17 pages
–2–
M15/4/CHEMI/HP2/ENG/TZ2/XX/M
This markscheme is the property of the International
Baccalaureate and must not be reproduced or distributed
to any other person without the authorization of the IB
Assessment Centre.
–3–
M15/4/CHEMI/HP2/ENG/TZ2/XX/M
Subject Details: Chemistry HL Paper 2 Markscheme
Mark Allocation
Candidates are required to answer ALL questions in Section A [40 marks] and TWO questions in
Section B [2 x 25 marks]. Maximum total = [90 marks].
1.
A markscheme often has more marking points than the total allows. This is intentional.
2.
Each marking point has a separate line and the end is shown by means of a semicolon (;).
3.
An alternative answer or wording is indicated in the markscheme by a slash (/). Either wording can
be accepted.
4.
Words in brackets ( ) in the markscheme are not necessary to gain the mark.
5.
Words that are underlined are essential for the mark.
6.
The order of marking points does not have to be as in the markscheme, unless stated otherwise.
7.
If the candidate’s answer has the same “meaning” or can be clearly interpreted as being of
equivalent significance, detail and validity as that in the markscheme then award the mark.
Where this point is considered to be particularly relevant in a question it is emphasized by
OWTTE (or words to that effect).
8.
Remember that many candidates are writing in a second language. Effective communication is
more important than grammatical accuracy.
9.
Occasionally, a part of a question may require an answer that is required for subsequent
marking points. If an error is made in the first marking point then it should be penalized. However,
if the incorrect answer is used correctly in subsequent marking points then follow through marks
should be awarded. When marking, indicate this by adding ECF (error carried forward) on the
script.
10.
Do not penalize candidates for errors in units or significant figures, unless it is specifically referred
to in the markscheme.
11.
If a question specifically asks for the name of a substance, do not award a mark for a correct
formula unless directed otherwise in the markscheme. Similarly, if the formula is specifically asked
for, unless directed otherwise in the markscheme do not award a mark for a correct name.
12.
If a question asks for an equation for a reaction, a balanced symbol equation is usually expected,
do not award a mark for a word equation or an unbalanced equation unless directed otherwise in
the markscheme.
13.
Ignore missing or incorrect state symbols in an equation unless directed otherwise in the
markscheme.
14.
Penalize missing hydrogens or incorrect bond linkages (eg C–H3C) once only.
–4–
M15/4/CHEMI/HP2/ENG/TZ2/XX/M
Section A
32
(a) (i)
31
30
Temperature / OC
1.
29
28
27
26
25
24
0.0
10.0
20.0
30.0
40.0
50.0
Volume of hydrochloric acid added / cm
3
drawing best-fit straight lines to show volume;
There should be approximately the same number of points above and
below for both lines.
27.0 (cm3);
Accept any value in the range 26.0 to 28.0 (cm3) if consistent with student’s
annotation on the graph.
Accept ECF for volumes in the range 27.0–30.0 cm3 if it corresponds to
maximum temperature of line drawn.
Volume should be given to one decimal place.
(ii)
1.00  0.0250
;
0.0270
 0.926mol dm3 ;
Volume of 26.0 gives [HCl] = 0.962 moldm–3. Volume of 28.0 gives [HCl] =
0.893 moldm–3.
Award [2] for correct final answer with units.
Award [1 max] for correct concentration without units.
Accept M, mol L–1, mol/dm3 as units.
[2]
([HCl]) 
[2]
–5–
(b)
(i)
(30.2  25.0  )(  )5.2( C/K) ;
Any accepted value must be consistent with student’s annotation on the
graph but do not accept T  5.1 .
Accept (+)5.6 (C/K) (ie, taking into account heat loss and using T when
volume = 0.0 cm3).
(ii)
Q   m  c  T  (25.0  27.0)  4.18  5.2  1130.272 J   1.13(kJ) ;
n  (1.00  0.0250 )0.0250(mol) ;
Q
H  (   45210.88 Jmol1 )  45(kJmol1 ) ;
n
Award [3] for correct final answer.
Award [2] for +45 (kJ mol –1).
Apply ECF for M3 even if both m and T are incorrect in M1.
Accept use of c = 4.2 Jg–1K–1.
(iii)
(iv)
2.
(a)
(b)
(c)
M15/4/CHEMI/HP2/ENG/TZ2/XX/M
 45  ( 58)

 100   22 (%) ;

( 58)


Answer must be given to two significant figures.
Ignore sign.
heat losses;
better (thermal) insulation / using a polystyrene cup / putting a lid on the
beaker;
Accept other suitable methods for better thermal insulation but do not
accept just “use a calorimeter” without reference to insulation.
change in concentration of reactant/product with time / rate of change of
concentration;
Accept “increase” instead of “change” for product and “decrease” instead of
“change” for reactant.
Accept “mass/amount/volume” instead of “concentration”.
Do not accept substance.
[1]
[3]
[1]
[2]
[1]
surface area decreases;
frequency/probability of collisions decreases;
Accept number of collisions per unit time decreases.
[2]
(i)
step 2 / X + NO → Y + H2O / slow;
[1]
(ii)
invalid / unlikely as order most likely one (with respect to hydrogen);
rate = k[NO]2[H2] / H2 only involved once in the formation of the
intermediate before the slow step / OWTTE;
Award M2 only if M1 is correct.
[2]
–6–
3.
M15/4/CHEMI/HP2/ENG/TZ2/XX/M
(a)
( 239.0  [ 110.5] )  128.5 (kJmol1 ) ;
[1]
(b)
( 166.0  [ 137.2]  )  28.8 (kJmol1 ) ;
[1]

 298  S Ö  
Ö
 G  28.8  128.5  
 
 1000  


1
( S Ö  )  335 (
);
[1]
(c)
K
1
l
o
m
J
(d)
S Ö   S Ö products   S Ö reactants / 335  126.8  197.6  2S ÖH2 ;
S ÖH2  (  )132(Jmol1 K 1 ) ;
[2]
Award [2] for correct final answer.
Award [1 max] for S ÖH2  (  )264(Jmol1 K 1 ) .
4.
(a)
(b)
a solution that resists changes in pH / changes pH slightly / OWTTE;
when small amounts of an acid/H+ or a base/alkali/OH– are added;
[2]
addition of acid:
CH3 CH2COO (aq)  H (aq)  CH3 CH2COOH(aq) / propanoate ions combine with
H+ ions to form undissociated propanoic acid;
addition of base:
CH3 CH2COOH(aq)  OH (aq)  CH3 CH2COO (aq)  H2O(l ) / addition of OH–
removes H+ and more propanoic acid dissociates/ionizes;
[2]
Ignore state symbols.
Accept reversible arrows.
Award [1 max] if correct equations are given without reference to addition of acid
or alkali.
(c)
Ka 
[H (aq)][CH3 CH2COO  (aq)]
 [base] 
/ pH  pK a  log 
;
[CH3 CH2 COOH(aq)]
 [acid] 

log 

H
O O
O O
C C
2
H H2
C C
H 3H 3
C C
K a  1.3  10 5 /10 4.87 and [H ]  1.3  10 4 /10 3.87 (mol dm3 ) /


 3.87  4.87  1;

7.41 

1
3
 [CH3 CH2COOH]  74.09   0.100/1.00  10 (mol dm ) ;


([CH3 CH2COONa]  ) 0.010/1.0  10 2 (mol dm3 ) ;
Award [4] for correct final answer.
Accept corresponding use of [H3O]+ for [H+], [acid] for [CH3CH2COOH], and
[base] or [salt] for [CH3CH2COO–] throughout.
[4]
–7–
5.
(a)
(b)
M15/4/CHEMI/HP2/ENG/TZ2/XX/M
same functional group;
same general formula;
(successive members) differ by CH2;
similar chemical properties;
gradation in physical properties;
Do not accept “same” instead of “similar”, or vice-versa.
Initiation:
UV / hf / h
Br2 
 2Br  ;
Reference to UV light or high temperatures must be included.
Propagation:
Br   C2H6  C2H5   HBr ;
C2H5   Br2  C2H5Br  Br  ;
Termination:
Br   Br   Br2 / C2H5   Br   C2H5Br / C2H5   C2H5   C4H10 ;
Accept representation of radical without  (eg, Br, C2H5) if consistent throughout
mechanism.
Penalize reference to heterolytic fission once only.
Award [0] to any mechanism involving ions.
Accept further bromination.
Award [3 max] if initiation, propagation and termination are not stated or are
incorrectly labelled for equations.
Accept correct description of processes without equations.
6.
(a)
[4]
Positive electrode (anode):
2Cl  (l )  Cl 2 (g)  2e / Cl  (l )  21 Cl 2 (g)  e ;
Negative electrode (cathode):
Mg2 (l )  2e  Mg(l ) ;
Accept e instead of e–.
Award [1 max] for correct half-equations given at the wrong electrode.
Penalize use of reversible arrows once only.
correct state symbols in both equations;
(b)
[2 max]
aluminium/Al is less dense (compared to iron/Fe) / Al is more ductile or malleable
/ aluminium forms a protective oxide layer / Al does not corrode / iron/Fe rusts /
OWTTE;
Do not accept “Al is lighter” OR “less expensive” OR “Al can be recycled”.
[3]
[1]
–8–
M15/4/CHEMI/HP2/ENG/TZ2/XX/M
Section B
7.
(a)
(i)
(ii)
rates of forward and reverse reactions are equal / opposing changes occur
at equal rates;
the concentrations of all reactants and products remain constant /
macroscopic properties remain constant;
closed/isolated system;
Accept “the same” for “equal” in M1 and for “constant” in M2.
The volume of the container is increased:
position of equilibrium shifts to the left/reactants and fewer moles of gas on
the right hand side/pressure decreases / OWTTE;
Ammonia is removed from the equilibrium mixture:
position of equilibrium shifts to the right/products and [NH3] decreases so
[N2] and [H2] must also decrease to keep Kc constant
OR
position of equilibrium shifts to the right/products and rate of reverse
reaction decreases / OWTTE;
Award [1 max] if both predicted changes are correct.
Do not accept “to increase [NH3]” or reference to LCP without explanation.
(iii)
(b)
minimum energy needed (by reactants/colliding particles) to react/start/
initiate a reaction;
Accept “energy difference between reactants and transition state”.
[2]
[1]
rate increases;
more effective/successful collisions per unit time / greater proportion of collisions
effective;
alternative pathway and a lower activation energy
OR
lowers activation energy so that more particles have enough energy to react;
Do not accept just “lowers/reduces the activation energy”.
Accept “provides a surface for reacting/reactants/reaction”.
(c)
[2 max]
(i)
(ii)
slower rate / OWTTE;
uneconomic / OWTTE;
high cost for building/maintaining plant / high energy cost of compressor /
OWTTE;
Do not accept “high pressure is expensive” without justification.
Accept high pressure requires high energy.
[2 max]
[2]
[1]
–9–
(d)
(i)
(ii)
M15/4/CHEMI/HP2/ENG/TZ2/XX/M
[NH3 (g)]2
;
[N2 (g)]  [H2 (g)]3
Ignore state symbols.
Concentrations must be represented by square brackets.
(K c  )
[1]
moles at equilibrium: nitrogen 0.27, hydrogen 0.81 / concentrations at
equilibrium: nitrogen 0.27 (mol dm–3), hydrogen 0.81 (mol dm–3) (and ammonia
1.46 mol dm–3);
K c  15 ;
[2]
(e)
9
7
0
.
0
=
2 1
6
4 ×
3
.
3
1
=
Kc
Actual calculation gives K c  14.86.
Award [2] for correct final answer.


Award [1 max] if




(i)
electron pair donor;
Accept lone pair donor.
[1]
(ii)
proton acceptor and partially/slightly ionized;
Accept “proton acceptor and partially/slightly dissociated”.
[1]
(iii)
Acid
Conjugate base
CH3NH3+
and
CH3NH2;
H2O
and
OH−;
[2]
Award [1 max] for two correct acids OR two correct conjugate bases.
(f)
Kb 
[NH4  ][OH ]
 1.8  10 5 / 10 4.75 ;
[NH3 ]
[NH4  ]  [OH ] and [NH3 ]  1.00  101 (mol dm3 ) ;
[OH ]  ( 1.8  106 )1.3  103 (mol dm3 ) / pOH  2.89 ;
pH  (14.0  2.89 )11.1;
Award [4] for correct final answer.
[4]
M15/4/CHEMI/HP2/ENG/TZ2/XX/M
– 10 –
(g)
(i)
12
pH
7
0
0
5
10
15
20
25
30
35
40
45
50
NH3(aq) volume / cm3
(ii)
For volume = 0: pH  1;
vertical jump should be positioned in volume range 24 cm3 to 26 cm3 and
include pH range between 3 to 6;
For volume = 50: pH between 8 to 11;
[3]
methyl orange / bromophenol blue / bromocresol green / methyl red;
[1]
– 11 –
8.
(a)
M15/4/CHEMI/HP2/ENG/TZ2/XX/M
(i)
[1]
4s
3d
Accept full-arrows.
Accept boxes in reverse order or at different energy levels.
Do not award the mark if sub-levels are incorrectly labelled or if no boxes are
drawn.
(ii)
(c)
[1]
(delocalized electrons allows) the layers/rows of cations/positive/Cr3+ ions
to slide past each other (without disrupting the metallic bonding);
Accept atoms instead of ions.
[1]
(i)
chromium(III) oxide;
Do not award the mark for chromium oxide.
[1]
(ii)
(electrostatic) attraction between positive and negative ions/oppositely
charged ions/Cr3+ and O2–;
formed as a result of electron transfer from chromium atoms to oxygen
atoms / OWTTE;
Ignore reference to number of electrons transferred or charges of ion for M2.
(iii)
(b)
(electrostatic) attraction between (lattice of) cations/positive/Cr3+ ions and
delocalized electrons;
[2]
(iii)
ions are not free to move (when solid) / ions in rigid lattice / OWTTE;
[1]
(i)
III / +3;
Do not cccept incorrect notation such as 3+/3.
[1]
(ii)
ligand has lone/non-bonding electron pair /
dative (covalent)/coordinate/coordination bond forms;
ligand is Lewis base / ion is Lewis acid;
(iii)
partially filled/incomplete d sub levels/orbitals;
d orbitals split into two levels;
energy difference is in visible part of spectrum / electrons absorb visible
light/one colour/frequency/wavelength;
electron transitions occur from lower to higher energy level (within
d sub-level);
complementary colour/colour not absorbed is seen;
Do not accept complementary colour "emitted".
[2]
[4 max]
– 12 –
M15/4/CHEMI/HP2/ENG/TZ2/XX/M
(iv)
[2]
Accept any other octahedral arrangement of ligands.
Ignore missing square brackets and charge.
(d)
(i)
Half equation:
I  (aq)  3H2O (l)  IO3  (aq)  6H (aq)  6e ;
Accept e instead of e–.
Accept reversible arrows.
Overall equation:
Cr2O7 2 (aq)  I  (aq)  8H (aq)  2Cr 3  (aq)  IO3  (aq)  4H2O (l ) ;
[2]
Ignore state symbols.
(e)
(ii)
oxidized and increase (in oxidation number) of 6/from –1/–I to +5/+V;
(i)
potential (of reduction half-reaction) under standard conditions measured
relative to standard hydrogen electrode/SHE / OWTTE;
Accept “solute concentration of 1 mol dm–3” or “1 bar/1 atm (pressure) for
gases” instead of “standard conditions”.
Accept voltage/emf for potential.
[1]
[1]
(ii)
(+)1.08 (V);
[1]
(iii)
2Cr (s)  3Cu2 (aq)  2Cr 3  (aq)  3Cu(s) ;
Ignore state symbols.
Do not accept reversible arrows.
[1]
(iv)
Negative electrode: chromium/Cr and Positive electrode: copper/Cu;
Accept “Cr is the anode and Cu the cathode".
[1]
(v)
from chromium/Cr to copper/Cu;
Accept “from negative electrode/anode to positive electrode/cathode” if
electrodes correctly identified in (iv).
[1]
(vi)
negative ions/anions towards the chromium(III) solution and positive
ions/cations towards the copper(II) solution / OWTTE;
[1]
– 13 –
9.
(a)
(i)
(ii)
M15/4/CHEMI/HP2/ENG/TZ2/XX/M
MgCl2 conducts electricity and PCl3 does not;
MgCl2 is ionic and PCl3 is covalent/molecular;
ions/charged particles can move in MgCl2 / no free charged particles in PCl3;
Award [1 max] if all three points correct for one substance but not other.
MgCl2:
4  pH  6.9 ;
high charge density/high charge and small size of Mg2+ makes [Mg(H2O)6]2+
hydrolyse / polarizes water to produce H+;
PCl3:
0  pH  4 ;
(reacts with water to) form HCl/H3PO3;
Do not accept H3PO4.
(b)
(i)
[3]
[4]
Na, Mg (oxides): basic
Al (oxide): amphoteric
Do not accept amphiprotic.
Si to Cl (oxides): acidic
[2]
Award [2] for all three listed sets correct.
Award [1] for one or two listed sets correct.
Award [1] for stating oxides become more acidic towards right/Cl or more
basic towards left/Na.
Do not penalize if reference is to Ar instead of Cl.
Do not penalize for incorrect formulas of oxides.
(ii)
Na 2 O (s)  H2 O (l )  2NaOH(aq) ;
P4 O10 (s)  6H2O(l )  4H3PO4 (aq) ;
[2]
Ignore state symbols.
Accept P2O5 (s) + 3H2O (l)  2H3PO4 (aq).
Do not award marks if incorrect formulas of the oxides are used.
(c)
(i)
[2]
Penalize lone pairs missing on Br and F once only.
Accept any combination of lines, dots or crosses to represent electron pairs.
– 14 –
(ii)
PBr3
Shape:
trigonal pyramidal;
Accept triangular pyramidal.
M15/4/CHEMI/HP2/ENG/TZ2/XX/M
SF4
Shape:
see-saw/K-shaped;
Accept distorted tetrahedral.
No ECF for shape if Lewis structure is incorrect.
Bond angle:
Any value 99  <109  ;
Literature value = 101  .
Bond angle:
Any two for [1] of:
(Feq–S–Feq): Any value 100  <120 
Literature value = 103 
(Fax–S–Fax): Any value 175  <185 
Literature value = 179  /180 
(Fax–S–Feq): Any value 85  < 95 
Literature value = 89 
No ECF for angle if shape is incorrect.
Do not award mark for correct angles if shape is incorrect.
(iii)
(d)
(i)
P–Br and S–F bonds are polar / bonds in both molecules are polar;
non-symmetrical distribution of electron cloud / polar bonds/dipoles do not
cancel because of non-symmetrical shape;
M2 may also be scored with a suitable diagram showing the vectorial
addition of the individual S–F dipole moments to show a net dipole moment
centred along the axis between the Feq–S–Feq bond.
[4]
[2]
EITHER
(electrostatic) attraction between (positively charged) nuclei and a pair of
electrons;
formed as a result of electron sharing (between the carbon and hydrogen
nuclei);
OR
(ii)
sigma bond formed by overlap of atomic orbitals;
s orbital from H and p/sp2 from carbon;
[2]
α: sp3 and : sp2;
[1]
Accept if numbers are given as subscripts.
(iii)
 bond:
end-on / axial overlap of two orbitals;
 bond:
sideways overlap of two (parallel) p orbitals;
[2]
Accept suitable diagrams for both marks.
(iv)
11  and 3 ;
[1]
M15/4/CHEMI/HP2/ENG/TZ2/XX/M
– 15 –
Penalize missing hydrogens only once in Question 10.
10.
(a)
(i)
;
[1]
Accept bromine atoms cis to each other.
(b)
(ii)
2,3-dibromobutane;
Do not penalize the incorrect use of spaces, comma or hyphen.
[1]
(iii)
red/brown/orange/yellow to colourless/decolourized;
Do not accept clear.
Do not accept just “decolorized”.
[1]
(i)
(synthesis of) plastics/polymers/organic materials not naturally available /
synthetic materials;
wide range of uses/physical properties / versatile;
large industry / many tons of plastics consumed by society / OWTTE;
Do not accept “useful” for M2.
Award [1 max] if specific addition polymer and its use is given.
Penalize reference to condensation polymers once only.
[2 max]
(ii)
[1]
Ignore n.
Brackets are not required for the mark, but continuation bonds are.
Do not penalize if methyl groups are trans to each other.
(c)
(i)
CH2CH3
HO
C
H3C
Br
H
CH2CH3
HO
C
CH2CH3
Br
+
C
H
HO
CH3 H
Br–
CH3
–
curly arrow going from lone pair/negative charge on O in HO to C;
Do not accept curly arrow originating on H in HO–.
curly arrow showing Br leaving;
Accept curly arrow either going from bond between C and Br to Br in
2-bromobutane or in the transition state.
Accept if arrow goes from C–Br bond to/or beyond Br.
representation of transition state showing negative charge, square brackets
and partial bonds;
Do not penalize if HO and Br are not at 180  to each other.
Do not award M3 if OH----C bond is represented.
formation of organic product CH3CHOHCH2CH3 and KBr/Br–;
[4]
– 16 –
(ii)
(d)
M15/4/CHEMI/HP2/ENG/TZ2/XX/M
OH– has a negative charge/higher electron density;
stronger attraction to the carbon atom with the partial positive charge /
OWTTE;
Do not accept just stronger attraction.
Reference to carbon atom needed for M2.
[2]
(i)
2-methylbutanenitrile;
Accept small errors in spelling.
Accept 2-cyanobutane.
Do not accept butan-2-nitrile.
[1]
(ii)
hydrogen/H2 and nickel/Ni;
Accept other suitable metal catalysts such as platinum/Pt, palladium/Pd.
[1]
(iii)
;
[1]
Accept condensed CH3 branch in structural formula as this was present in
structure given in question.
(e)
(i)
carbonyl;
Accept ketone.
[1]
(ii)
;
[1]
Accept condensed or full structural formula.
(f)
(g)
hydrogen bonding in compound C;
dipole-dipole forces in C / C is more polar;
C has greater molar mass/more dispersion/London/instantaneous induced dipoleinduced dipole forces/van der Waal forces;
Accept converse argument.
Award [1 max] for stronger intermolecular forces.
C4H9 OH(l )  6O2 (g)  4CO2 (g)  5H2O(l ) ;
Ignore state symbols.
[2 max]
[1]
– 17 –
(h)
(i)
(ii)
M15/4/CHEMI/HP2/ENG/TZ2/XX/M
compounds with the same structural formula and different arrangement in
space/3D structures;
Accept molecular formula instead of structural formula.
Do not accept “similar” instead of “same”.
restricted rotation around a (double) bond;
carbon atoms of the C=C/carbon-carbon double bond (in alkene)/carbon
atoms of the C–C/carbon-carbon single bond (in cycloalkane) must have
two different atoms/groups of atoms / OWTTE;
Do not accept “functional groups” for “groups of atoms” in M2.
[1]
[2]
(iii)
[2]
Award [1 max] if cis and trans isomers are correctly drawn and identified
for alkene other than but-2-ene.
Award [1 max] if student draws and labels one structure correctly but not
the other.
N15/4/CHEMI/HPM/ENG/TZ0/XX
Chemistry
Higher level
Paper 1
Friday 13 November 2015 (afternoon)
1 hour
Instructions to candidates
• Do not open this examination paper until instructed to do so.
• Answer all the questions.
• For each question, choose the answer you consider to be the best and indicate your choice on
the answer sheet provided.
• The periodic table is provided for reference on page 2 of this examination paper.
• The maximum mark for this examination paper is [40 marks].
15 pages
8815 – 6101
© International Baccalaureate Organization 2015
23
V
50.94
87
Fr
(223)
88
Ra
(226)
‡
†
89 ‡
Ac
(227)
90
Th
232.04
58
Ce
140.12
91
Pa
231.04
59
Pr
140.91
73
Ta
180.95
38
Sr
87.62
37
Rb
85.47
22
Ti
47.90
56
57 †
72
55
Ba
La
Cs
Hf
132.91 137.34 138.91 178.49
20
Ca
40.08
19
K
39.10
41
Nb
92.91
39
Y
88.91
12
Mg
24.31
11
Na
22.99
92
U
238.03
60
Nd
144.24
74
W
183.85
42
Mo
95.94
24
Cr
52.00
Relative Atomic Mass
Element
Atomic number
40
Zr
91.22
21
Sc
44.96
4
Be
9.01
2
3
Li
6.94
1
H
1.01
1
30
Zn
65.37
32
Ge
72.59
31
Ga
69.72
33
As
74.92
34
Se
78.96
16
S
32.06
10
Ne
20.18
18
Ar
39.95
36
Kr
83.80
17
Cl
35.45
35
Br
79.90
2
He
4.00
0
9
F
19.00
7
84
Po
(210)
85
At
(210)
93
Np
(237)
94
Pu
(242)
95
Am
(243)
96
Cm
(247)
97
Bk
(247)
98
Cf
(251)
99
Es
(254)
100
Fm
(257)
101
Md
(258)
102
No
(259)
103
Lr
(260)
61
66
68
62
67
69
63
70
64
71
65
Pm
Dy
Sm
Tm
Lu
Tb
Er
Ho
Eu
Yb
Gd
146.92 150.35 151.96 157.25 158.92 162.50 164.93 167.26 168.93 173.04 174.97
75
80
82
76
81
83
77
78
79
Re
Pb
Os
Tl
Bi
Pt
Au
Hg
Ir
186.21 190.21 192.22 195.09 196.97 200.59 204.37 207.19 208.98
86
Rn
(222)
49
48
54
50
44
51
45
52
46
53
47
In
I
Cd
Sn
Xe
Ru
Sb
Rh
Te
Pd
Ag
101.07 102.91 106.42 107.87 112.40 114.82 118.69 121.75 127.60 126.90 131.30
29
Cu
63.55
15
P
30.97
8
O
16.00
6
43
Tc
98.91
28
Ni
58.71
14
Si
28.09
13
Al
26.98
7
N
14.01
5
26
Fe
55.85
6
C
12.01
4
5
B
10.81
3
25
Mn
54.94
27
Co
58.93
The Periodic Table
–2–
N15/4/CHEMI/HPM/ENG/TZ0/XX
–3–
1.
2.
N15/4/CHEMI/HPM/ENG/TZ0/XX
Which compound’s molecular formula is the same as its empirical formula?
A.
C2H5OH
B.
CH3COOH
C.
C6H6
D.
C8H18
The equation for the complete combustion of propene, C3H6 , is shown below.
2C3H6 (g) + 9O2 (g) → 6CO2 (g) + 6H2O (l)
Which mixture, when ignited, will lead to incomplete combustion and the formation of CO (g)?
3.
A.
2 dm3 of propene and 10 dm3 of oxygen
B.
0.5 dm3 of propene and 2.3 dm3 of oxygen
C.
1 dm3 of propene and 4 dm3 of oxygen
D.
3 dm3 of propene and 14 dm3 of oxygen
What is the percentage yield when 1.1 g of ethanal, CH3CHO, is obtained from 4.6 g of ethanol,
CH3CH2OH? Mr (CH3CH2OH) = 46; Mr (CH3CHO) = 44
CH3CH2OH (l) + [O] → CH3CHO (l) + H2O (l)
A.
B.
1.1× 46 × 100
44 × 4.6
1.1× 100
4 .6
C.
4.6 × 44 × 100
4 .6 × 1 .1
D.
1.1× 46
44 × 4.6
Turn over
–4–
5.
Which stage of operation immediately follows ionization in the mass spectrometer?
A.
Acceleration
B.
Deflection
C.
Detection
D.
Vaporization
Which statement is correct about the first ionization energies of consecutive elements shown in
the graph?
2000
First ionization energy / kJ mol–1
4.
N15/4/CHEMI/HPM/ENG/TZ0/XX
1500
1000
500
3
4
5
6
7
8
9
10
Atomic number
[Source: Values from Nuffied Advance Science - Book of Data, Revised Edition (1984)]
A.
The graph falls between Be and B because there is an electron in the third energy level.
B.
The graph increases from B to N because the atomic radius is increasing.
C.
The graph increases from Li to Ne because the number of electrons is increasing.
D.
The graph falls between Be and B because the outer electron in B is in a p sub-level.
–5–
6.
7.
8.
9.
10.
N15/4/CHEMI/HPM/ENG/TZ0/XX
Which element has the greatest first ionization energy?
A.
Al
B.
Ar
C.
Cl
D.
Cs
Which elements are in the same group of the periodic table?
A.
Ca, Na, Rb, Sr
B.
Al, Ar, Cl, S
C.
Au, Hg, Pb, Pt
D.
As, Bi, P, Sb
Which property of transition metals enables them to behave as catalysts?
A.
High melting point
B.
Variable oxidation number
C.
High density
D.
Split d sub-levels
Which statement best describes the lattice structure of solid sodium chloride?
A.
Each sodium ion is surrounded by one chloride ion.
B.
Each chloride ion is surrounded by two sodium ions.
C.
Each chloride ion is surrounded by four sodium ions.
D.
Each sodium ion is surrounded by six chloride ions.
Which compound is most likely to contain ionic bonding?
A.
ClO2
B.
CsCl
C.
SCl2
D.
SiCl4
Turn over
–6–
11.
12.
13.
14.
N15/4/CHEMI/HPM/ENG/TZ0/XX
Which molecule is polar?
A.
C2H6
B.
CH2Cl2
C.
CO2
D.
CCl4
What is the shape of the hexacyanoferrate(III) ion, [Fe(CN)6]3-?
A.
Square planar
B.
Hexagonal
C.
Octahedral
D.
Trigonal bipyramidal
Which set contains two or more species with delocalized π electrons?
A.
CH3CH3 , H2C=CH2 , H2C=O
B.
NaCl , C6H6 , H2C=O
C.
CO32- , C6H6 , C6H12
D.
O2 , CH3COCH3 , CH3COOCH3
Which of the following changes are exothermic?
I.
H2SO4 (aq) + 2NaOH (aq) → Na2SO4 (aq) + 2H2O (l)
II.
2C8H18 (g) + 17O2 (g) → 16CO (g) + 18H2O (g)
III.
C8H18 (g) → C8H18 (l)
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
–7–
15.
16.
17.
18.
N15/4/CHEMI/HPM/ENG/TZ0/XX
Which change represents the standard enthalpy change of formation?
A.
The formation of 1 mol of a compound in its standard state from its gaseous atoms
B.
The formation of 1 mol of a compound in its standard state from its elements
C.
The formation of 1 mol of a compound in its standard state from its gaseous atoms in their
standard states
D.
The formation of 1 mol of a compound in its standard state from its elements in their
standard states
Which equation represents electron affinity?
A.
C (g) + e− → C− (g)
B.
Na+ (aq) + e− → Na (s)
C.
1
2 Cl2 (g)
D.
B (g) + e− → B+ (g) + 2e−
+ e− → Cl− (g)
Which combination results in an ionic compound having the greatest magnitude of lattice
enthalpy?
Sum of ionic radii
Ionic charges
A.
small
large
B.
large
large
C.
large
small
D.
small
small
Under which conditions does a sample of the same mass of carbon dioxide have the lowest
entropy value?
A.
Solid at high temperature
B.
Solid at low temperature
C.
Gas at high temperature
D.
Gas at low temperature
Turn over
–8–
Curves I and II represent samples of the same gas at a constant pressure but at different
temperatures. The areas under curves I and II are equal. What does curve II represent?
Probability of molecules
with kinetic energy E
19.
N15/4/CHEMI/HPM/ENG/TZ0/XX
I
II
Kinetic energy E
A.
Curve II is at the lower temperature and there are less molecules in the sample.
B.
Curve II is at the lower temperature and there are the same number of molecules in
the samples.
C.
Curve II is at the higher temperature and there are more molecules in the sample.
D.
Curve II is at the higher temperature and there are the same number of molecules in
the samples.
–9–
20.
N15/4/CHEMI/HPM/ENG/TZ0/XX
The graph shows a plot for a reaction with second-order kinetics. How should the axes be
labelled?
y
x
21.
x-axis
y-axis
A.
concentration
time
B.
time
concentration
C.
rate
concentration
D.
concentration
rate
Which factors affect the rate constant, k, of a reaction?
I.
Catalyst
Concentration of reactants
II.
III.
Temperature
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
Turn over
– 10 –
22.
23.
N15/4/CHEMI/HPM/ENG/TZ0/XX
Which best describes a reaction in a state of equilibrium?
A.
The rates of the forward and reverse reactions are zero and the concentrations of products
and reactants are equal.
B.
The rate of the forward reaction equals the rate of the reverse reaction and the
concentrations of products and reactants are equal.
C.
The rates of the forward and reverse reactions are zero and the concentrations of products
and reactants are constant.
D.
The rate of the forward reaction equals the rate of the reverse reaction and the
concentrations of products and reactants are constant.
The equilibrium concentrations of X, Y, Z and W are 1, 2, 4 and 2 mol dm–3 respectively.
X (g) + 2Y (g)  Z (g) + W (g)
What is the value of the equilibrium constant, Kc?
24.
25.
A.
0.25
B.
0.5
C.
2
D.
4
Which of the following molecules can act as a Lewis acid but not as a Brønsted–Lowry acid?
A.
BF3
B.
PCl3
C.
NH3
D.
H2 O
Which is a 0.001 mol dm-3 solution of a weak acid?
Conductivity
pH
A.
poor
5
B.
good
7
C.
poor
10
D.
good
3
– 11 –
26.
N15/4/CHEMI/HPM/ENG/TZ0/XX
What is the order of increasing acid strength? Approximate Ka and pKa values at 298 K are given.
pKa
Ka
27.
28.
ClCH2COOH
1×10−3
C6H5OH
10.0
CH3CH2COOH
1×10−5
C6H5NH3+
4.6
A.
ClCH2COOH < CH3CH2COOH < C6H5NH3+ < C6H5OH
B.
C6H5OH < C6H5NH3+ < ClCH2COOH < CH3CH2COOH
C.
C6H5OH < C6H5NH3+ < CH3CH2COOH < ClCH2COOH
D.
C6H5OH < CH3CH2COOH < C6H5NH3+ < ClCH2COOH
Which solutions, mixed in equal concentrations and volumes, form an acid buffer solution?
A.
HCl (aq) + NaCl (aq)
B.
CH3CO2H (aq) + CH3CO2Na (aq)
C.
CH3CO2H (aq) + NaOH (aq)
D.
CH3CO2H (aq) + CH3CH2CO2H (aq)
Which salt forms the most acidic solution when dissolved in water?
Salt
Ionic radius of cation / 10–12 m
A.
CrCl3
63
B.
FeCl2
76
C.
MgCl2
65
D.
NaCl
98
Turn over
– 12 –
29.
N15/4/CHEMI/HPM/ENG/TZ0/XX
What is the buffer region in the acid–base titration curves below?
D
10
10
pH
B
5
pH
5
C
A
0
Volume of alkali added
30.
0
Volume of alkali added
Which element undergoes reduction in the following reaction?
(NH4)2Cr2O7 (s) → N2 (g) + 4H2O (l) + Cr2O3 (s)
31.
A.
Cr
B.
H
C.
N
D.
O
Which best describes reduction?
A.
Increase in oxidation number and gain of electrons
B.
Increase in oxidation number and loss of electrons
C.
Decrease in oxidation number and gain of electrons
D.
Decrease in oxidation number and loss of electrons
– 13 –
32.
N15/4/CHEMI/HPM/ENG/TZ0/XX
What is E À, in V, for the following reaction?
VO2+ (aq) + 2H+ (aq) + V2+ (aq) → 2V3+ (aq) + H2O (l)
Standard electrode potential, E À / V
33.
34.
V2+ (aq) + 2e−  V (s)
−1.18
V3+ (aq) + e−  V2+ (aq)
−0.26
VO2+ (aq) + 2H+ (aq) + e−  V3+ (aq) + H2O (l)
+0.34
VO2+ (aq) + 2H+ (aq) + e−  VO2+ (aq) + H2O (l)
+1.00
A.
−0.60
B.
+0.08
C.
+0.60
D.
+1.26
What product is formed at the positive electrode (anode) when 0.001 mol dm–3 H2SO4 (aq) is
electrolysed?
A.
Hydrogen
B.
Oxygen
C.
Sulfur
D.
Sulfur dioxide
Which pair of compounds can be distinguished by reacting them with dilute bromine water in
the dark?
A.
CH3CH2COOH and CH3CH2CHO
B.
CH3CH2CHCHCH3 and CH3CH2CH2CH2CH3
C.
CH3CH2CH(CH3)2 and CH3CH2CH2CH2CH3
D.
CH3CH2CH2CHBrCH3 and CH3CH2CHBrCH2CH3
Turn over
– 14 –
35.
36.
Which compound is most soluble in water?
A.
CH3CH2CHO
B.
CH3CH2CH2CHO
C.
CH3CH2CO2H
D.
CH3CH2CH2CO2H
Which are features of successive members of a homologous series?
I.
II.
III.
37.
38.
N15/4/CHEMI/HPM/ENG/TZ0/XX
Similar chemical properties
Same general formula
Differ by −CH2−
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
Which formula represents propanenitrile?
A.
CH3CH2CN
B.
CH3CH2CH2CN
C.
CH3CH2CH2NH2
D.
CH3CH(NH2)CH3
Which halogenoalkane reacts fastest with warm NaOH (aq)?
A.
(CH3)3CCl
B.
(CH3)3CBr
C.
CH3CH2CH2CH2Cl
D.
CH3CH2CH2CH2Br
– 15 –
39.
N15/4/CHEMI/HPM/ENG/TZ0/XX
Which is the geometric isomer of cis-1,2-dichlorocyclopropane?
H
A.
Cl
B.
C
C
H
C
C
C
C
Cl
Cl
H
Cl
H
Cl
C.
H
H
H
Cl
D.
C
C
40.
Cl
H
H
H
H
C
C
Cl
H
C
Cl
C
H
Which is the best-fit line or best-fit curve for the points plotted on the graph?
A.
B.
C.
D.
N15/4/CHEMI/HPM/ENG/TZ0/XX/M
Markscheme
November 2015
Chemistry
Higher level
Paper 1
2 pages
–2–
N15/4/CHEMI/HPM/ENG/TZ0/XX/M
1.
A
16.
A
31.
C
46.
–
2.
C
17.
A
32.
C
47.
–
3.
A
18.
B
33.
B
48.
–
4.
A
19.
D
34.
B
49.
–
5.
D
20.
D
35.
C
50.
–
6.
B
21.
B
36.
D
51.
–
7.
D
22.
D
37.
A
52.
–
8.
B
23.
C
38.
B
53.
–
9.
D
24.
A
39.
C
54.
–
10.
B
25.
A
40.
C
55.
–
11.
B
26.
D
41.
–
56.
–
12.
C
27.
B
42.
–
57.
–
13.
C
28.
A
43.
–
58.
–
14.
D
29.
C
44.
–
59.
–
15.
D
30.
A
45.
–
60.
–
N15/4/CHEMI/HP2/ENG/TZ0/XX
Chemistry
Higher level
Paper 2
Friday 13 November 2015 (afternoon)
Candidate session number
2 hours 15 minutes
Instructions to candidates








Write your session number in the boxes above.
Do not open this examination paper until instructed to do so.
Section A: answer all questions.
Section B: answer two questions.
Write your answers in the boxes provided.
A calculator is required for this paper.
A clean copy of the chemistry data booklet is required for this paper.
The maximum mark for this examination paper is [90 marks].
8815 – 6102
© International Baccalaureate Organization 2015
28 pages
28EP01
–2–
N15/4/CHEMI/HP2/ENG/TZ0/XX
Section A
Answer all questions. Write your answers in the boxes provided.
1.
A student used the technique of titration to determine the concentration of ascorbic acid
(C6H8O6) in a sample of orange juice. Excess potassium iodide, KI (aq), was added to
acidified orange juice. The resulting solution was titrated with potassium iodate, KIO3 (aq),
in the presence of starch as an indicator. The end-point of the titration was shown by a
blue-black colour.
Step 1
IO3− (aq) + 5I− (aq) + 6H+ (aq) → 3I2 (aq) + 3H2O (l)
Iodine is only slightly soluble in water; but in the presence of excess iodide ions, I− (aq),
it forms the soluble tri-iodide ion, I3− (aq).
Step 2
I2 (aq) + I− (aq)  I3− (aq)
Ascorbic acid reacts with tri-iodide ions as follows.
Step 3
C6H8O6 (aq) + I3− (aq) → C6H6O6 (aq) + 2H+ (aq) + 3I− (aq)
(a)
Deduce the changes in oxidation number of iodine in step 1.
(i)
[2]
IO3− to I2:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I− to I2:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Identify the oxidizing and reducing agents in step 1.
Oxidizing agent:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reducing agent:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
28EP02
[1]
–3–
N15/4/CHEMI/HP2/ENG/TZ0/XX
(Question 1 continued)
(b)
Calculate the mass, in g, of potassium iodate, KIO3(s), which was required to prepare
0.250 dm3 of a 2.00 × 10−3 mol dm−3 solution.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(c)
The concentration of KIO3 used in the titration was 2.00 × 10−3 mol dm−3.
The titration produced the following results.
Titration 1
Titration 2
Titration 3
Final volume of KIO3 (± 0.05 cm3)
7.10
14.40
21.60
Initial volume of KIO3 (± 0.05 cm3)
0.00
7.10
14.40
Volume added of KIO3 (± 0.10 cm3)
7.10
7.30
7.20
Mean volume added of KIO3 (± 0.10 cm3)
(i)
7.20
Calculate the percentage uncertainty associated with the mean volume of
KIO3 (aq).
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
The colour of orange juice interfered with the blue-black colour at the equivalence
point. State the name of this type of error and suggest how this can be
minimized.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
28EP03
–4–
N15/4/CHEMI/HP2/ENG/TZ0/XX
(Question 1 continued)
(iii)
Determine the amount, in mol, of KIO3 (aq), in the mean volume.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (d)
Determine the amount, in mol, of ascorbic acid, C6H8O6 (aq), in the sample of acidified
orange juice.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(e)
Calculate the mass, in g, of ascorbic acid, C6H8O6 (aq), present in the sample of
acidified orange juice.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(This question continues on the following page)
28EP04
[1]
–5–
N15/4/CHEMI/HP2/ENG/TZ0/XX
(Question 1 continued)
(f)
The student found by further experimentation that oxidation of ascorbic acid follows
1
first-order kinetics. The graph of ln k against is shown below.
T
Determine the activation energy to three significant figures, including units.
0.0030
0.0031
1
/ K−1
T
0.0032
0.0033
0.0034
0.0035
[3]
0.0036
-10.4
-10.5
ln k
-10.6
-10.7
-10.8
-10.9
-11.0
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Turn over
28EP05
–6–
2.
(a)
N15/4/CHEMI/HP2/ENG/TZ0/XX
State the full electron configurations of copper, Cu, and copper (II) ion, Cu2+.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(b)
Cu2+ (aq) reacts with ammonia to form the complex ion [Cu (NH3)4]2+.
Explain this reaction in terms of acid-base theory, and outline the bonding in the
complex formed between Cu2+ and NH3.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(c)
Explain why complexes of Zn2+ (aq) are colourless whereas complexes of Cu2+ (aq)
are coloured.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
28EP06
[4]
–7–
3.
N15/4/CHEMI/HP2/ENG/TZ0/XX
Propane, C3H8 (g), undergoes complete combustion to form carbon dioxide, CO2 (g), and
water, H2O (g).
(a)
State an equation for the complete combustion of propane, C3H8 (g).
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(b)
Calculate the standard enthalpy change for the reaction in part (a) using bond enthalpy
values given in table 10 of the data booklet.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Turn over
28EP07
–8–
4.
(a)
(b)
N15/4/CHEMI/HP2/ENG/TZ0/XX
The monomers hexanedioic acid and 1,6-diaminohexane react together to form a
synthetic polymer.
Deduce the structural formula of each monomer.
[2]
State the type of polymerization reaction that occurs between these two monomers and
identify the structural feature needed in the monomers.
[2]
Type:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Structural feature:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(c)
Draw the structure of the linkage formed in this polymer, and identify the other product
of this polymerization reaction.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
28EP08
[2]
–9–
5.
(a)
(i)
N15/4/CHEMI/HP2/ENG/TZ0/XX
Define the term electronegativity.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Suggest why the noble gases are generally not assigned electronegativity values.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
Explain why the melting points of the group 1 metals (Li → Cs) decrease down the group
[3]
whereas the melting points of the group 7 elements (F → I) increase down the group.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(c)
Outline one reason why the sodium ion, Na+, has a smaller radius than the sodium
atom.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Turn over
28EP09
– 10 –
N15/4/CHEMI/HP2/ENG/TZ0/XX
Section B
Answer two questions. Write your answers in the boxes provided.
6.
Iron (III) oxide is the main source of iron but the decomposition of Fe2O3 (s) into its elements
is extremely difficult due to a large positive value of ∆G À.
(a)
Consider the following reactions:
Fe2O3 (s) → 2Fe (s) +
3
O2 (g)
2
∆G À = +742 kJ mol-1
1
O2 (g) → CO2 (g)
∆G À = −257 kJ mol-1
2
Suggest, with a reason, whether it is possible to produce iron by reacting Fe2O3 with CO.
CO (g) +
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(b)
The thermite reaction is one of the most exothermic reactions.
Fe2O3 (s) + 2Al (s) → 2Fe (l) + Al2O3 (s)
(i)
∆H À = −825.2 kJ
Species
S À / J K-1 mol-1
∆G Àf / kJ mol-1
Al (s)
+28.3
0
Al2O3 (s)
+50.9
−1582
Fe (l)
+34.8
+10.0
Fe2O3 (s)
+87.5
−742
Calculate the standard free energy change, ∆G À, in kJ mol-1, by using values of
the standard free energy change of formation, ∆G Àf , from the table above.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
28EP10
[2]
– 11 –
N15/4/CHEMI/HP2/ENG/TZ0/XX
(Question 6 continued)
(ii)
Calculate the standard entropy change, ∆S À, in J K-1 mol-1, by using values of
standard entropy, S À, from the table.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(iii)
Calculate the standard free energy change, ∆G À, for the reaction using ∆H À and
∆S À values at 25ûC.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(c)
(i)
Deduce the type of hybridization shown by the nitrogen atoms in NF4+, N2H2 and
N2H4.
NF4+
Hybridization
(ii)
N 2H 2
[3]
N 2H 4
............... ............... ...............
Describe how sigma (σ) and pi (π) bonds form.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(This question continues on the following page)
Turn over
28EP11
– 12 –
N15/4/CHEMI/HP2/ENG/TZ0/XX
(Question 6 continued)
(iii)
(d)
(i)
Draw the Lewis (electron dot) structures of SF4 and SF6. Use the valence shell
electron pair repulsion (VSEPR) theory to predict the name of the shape of each
molecule.
[4]
List the following compounds in order of increasing boiling point:
CH3CHO, CH3CH2CH3, CH3COOH, CH3CH2OH.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Explain the order of boiling points in the compounds listed in part (d) (i), in terms
of intermolecular forces.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
28EP12
[4]
– 13 –
N15/4/CHEMI/HP2/ENG/TZ0/XX
(Question 6 continued)
(e)
In the operation of a mass spectrometer, the first stage is vaporization and the last is
detection. State the names of the other three stages and outline what happens in
each one.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Turn over
28EP13
– 14 –
7.
(a)
N15/4/CHEMI/HP2/ENG/TZ0/XX
The following reaction is used in industry to obtain hydrogen from natural gas by partial
oxidation with steam.
CH4 (g) + H2O (g)  3H2 (g) + CO (g)
(i)
∆H À = +206 kJ
Describe the effect, if any, of each of the following changes on the equilibrium
amount of hydrogen, giving a reason in each case.
[4]
Increasing the pressure, at constant temperature:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Increasing the temperature, at constant pressure:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Discuss the effects of adding a solid catalyst to the mixture of methane and
steam, at constant pressure and temperature.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii)
Deduce the equilibrium constant expression, Kc , for the reaction.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
28EP14
[1]
– 15 –
N15/4/CHEMI/HP2/ENG/TZ0/XX
(Question 7 continued)
(iv)
Identify which of the changes in part (a) (i) will affect the value of Kc and whether
the value will increase or decrease.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
The equilibrium constant, Kc , for the reaction
CO (g) + H2O (g)  H2 (g) + CO2 (g)
was found to be 10.0 at 420ûC.
1.00 mol of CO (g) and 1.00 mol of H2O (g) are mixed in a 1.00 dm3 container at 420ûC.
Calculate the equilibrium concentration of each component in the mixture, showing
your working.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(This question continues on the following page)
Turn over
28EP15
– 16 –
N15/4/CHEMI/HP2/ENG/TZ0/XX
(Question 7 continued)
(c)
The oxidation of nitrogen monoxide takes place as follows:
2NO (g) + O2 (g) → 2NO2 (g)
The following experimental data was obtained at 101.3 kPa and 298 K.
(i)
Experiment
Initial [NO] /
mol dm−3
Initial [O2] /
mol dm−3
Initial rate /
mol dm−3 s−1
1
2.30 × 10−2
1.15 × 10−2
1.05 × 10−3
2
2.30 × 10−2
2.30 × 10−2
2.09 × 10−3
3
4.60 × 10−2
4.60 × 10−2
1.68 × 10−2
Deduce the orders of reaction with respect to O2 and NO.
[2]
Order with respect to O2:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Order with respect to NO:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
State the rate expression for the reaction.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii)
Calculate the value of the rate constant, k, and include its units.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
28EP16
[2]
– 17 –
N15/4/CHEMI/HP2/ENG/TZ0/XX
(Question 7 continued)
(iv)
Suggest a mechanism that is consistent with the rate expression, indicating the
rate-determining step.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (d)
Consider the following spontaneous reactions.
Fe (s) + Ni2+ (aq) → Fe2+ (aq) + Ni (s)
Zn (s) + Fe2+ (aq) → Zn2+ (aq) + Fe (s)
Ni (s) + Pb2+ (aq) → Ni2+ (aq) + Pb (s)
(i)
Deduce the order of increasing reactivity of the metals based on the reactions
above.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Identify the strongest oxidizing agent in the reactions above.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
28EP17
– 18 –
N15/4/CHEMI/HP2/ENG/TZ0/XX
(Question 7 continued)
(e)
Deduce the half-equations for the formation of the major product at the positive
electrode (anode) when the following aqueous solutions are electrolysed.
Dilute sodium chloride:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Concentrated sodium chloride:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
28EP18
[2]
– 19 –
N15/4/CHEMI/HP2/ENG/TZ0/XX
Please do not write on this page.
Answers written on this page
will not be marked.
Turn over
28EP19
– 20 –
8.
(a)
N15/4/CHEMI/HP2/ENG/TZ0/XX
20.0 cm3 aqueous solutions of two bases, each with a concentration of 0.100 mol dm−3
were separately titrated with 0.100 mol dm−3 hydrochloric acid, HCl (aq), and the
following graph was obtained.
14
13
I
12
11
10
II
9
8
pH
7
6
5
4
3
2
1
0
0
2
4
6
8
10
12
14
3
Volume of HCl / cm
(This question continues on the following page)
28EP20
16
18
20
22
– 21 –
N15/4/CHEMI/HP2/ENG/TZ0/XX
(Question 8 continued)
(i)
Deduce the pH at the equivalence points for base I and base II.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Suggest why the titration curve for base I is different from base II.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii)
State the formulas of two possible bases which could be used as base I.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv)
Calculate, using data from the graph, the dissociation constant, Kb, of base II,
showing your working.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (v)
Suggest an indicator that can be used for both titrations.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
28EP21
– 22 –
N15/4/CHEMI/HP2/ENG/TZ0/XX
(Question 8 continued)
(b)
(i)
State what is meant by the term buffer solution.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Calculate the pH of a solution prepared by mixing 40.0 cm3 of 0.200 mol dm–3
NH3 (aq) and 40.0 cm3 of 0.100 mol dm–3 HCl (aq), showing your working.
(pKb NH3 = 4.75 at 298 K)
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (c)
The equations of two acid-base reactions are given below.
(i)
Reaction A
H2CO3 (aq) + H2O (l)  HCO3− (aq) + H3O+ (aq)
Reaction B
HCO3− (aq) + H2O (l)  CO32− (aq) + H3O+ (aq)
Explain whether HCO3− (aq) behaves as an acid or a base in each of the
reactions A and B.
Reaction A:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reaction B:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
28EP22
[2]
– 23 –
N15/4/CHEMI/HP2/ENG/TZ0/XX
(Question 8 continued)
(ii)
Deduce two conjugate acid-base pairs from reactions A and B.
Acid
[2]
Base
Conjugate acid-base pair 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Conjugate acid-base pair 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(d)
Nitric acid, HNO3, and nitrous acid, HNO2, are described as strong and weak acids
respectively.
(i)
Distinguish between strong and weak acids.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
A 1.00 g sample of solid magnesium carbonate, MgCO3, is added to separate
solutions of HNO3 and HNO2 of the same concentration and temperature. State
one similarity and one difference in the observations made in these reactions.
[2]
Similarity:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Difference:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
28EP23
– 24 –
N15/4/CHEMI/HP2/ENG/TZ0/XX
(Question 8 continued)
(iii)
A solution of HNO3 has a pH of 1, while a solution of HNO2 has a pH of 5.
Determine the ratio of the hydrogen ion concentration in HNO3:HNO2.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (e)
(i)
State the acid-base character of the oxides of the period 3 elements Na to Ar.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
State balanced equations to illustrate the acid-base character of sodium oxide
and sulfur trioxide.
Sodium oxide:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sulfur trioxide:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28EP24
[2]
– 25 –
9.
(a)
N15/4/CHEMI/HP2/ENG/TZ0/XX
A 0.842 g sample of a liquid halogenoalkane, RBr(l), was heated under reflux with
1.35 × 10−2 mol of aqueous sodium hydroxide, NaOH (aq). After cooling the mixture, the
excess NaOH was titrated with hydrochloric acid, HCl (aq), and required 7.36 × 10−3 mol
of the acid.
(i)
State the equation for the substitution reaction of the halogenoalkane with sodium
hydroxide.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Calculate the amount, in mol, of sodium hydroxide that reacted with the
halogenoalkane.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii)
Calculate the molar mass of the halogenoalkane.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv)
Given that each molecule of the halogenoalkane contains one bromine atom,
determine its molecular formula.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
28EP25
– 26 –
N15/4/CHEMI/HP2/ENG/TZ0/XX
(Question 9 continued)
(b)
(v)
Deduce the structural formulas of four structural isomers of the halogenoalkane
based on the molecular formula and label each isomer as primary, secondary or
tertiary.
(If you have not been able to determine the molecular formula in part (a) (iv), use
C5H11Br to deduce the four structural isomers.)
[4]
The reaction between a primary halogenoalkane drawn in part (a) (v) and potassium
cyanide follows a SN2 mechanism.
(i)
State the importance of this reaction in organic synthesis.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
28EP26
[1]
– 27 –
N15/4/CHEMI/HP2/ENG/TZ0/XX
(Question 9 continued)
(ii)
Explain the mechanism of the reaction using curly arrows to represent the
movement of electron pairs.
[4]
(iii)
The organic product obtained in part (b) (ii) can be reduced to form an amine.
State an equation for this reaction and a suitable catalyst.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (c)
The reaction between the primary halogenoalkane, obtained in part (a) (v), and hot,
concentrated alcoholic NaOH is an example of an elimination reaction.
(i)
Explain the mechanism of the elimination reaction using curly arrows to represent
the movement of electron pairs.
[4]
(This question continues on the following page)
Turn over
28EP27
– 28 –
N15/4/CHEMI/HP2/ENG/TZ0/XX
(Question 9 continued)
(ii)
Under certain conditions, the major product obtained in the elimination reaction
can undergo polymerization. Identify the type of polymerization and draw a
section of the polymer consisting of two repeating units.
[2]
Type of polymerization:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Section of polymer:
(d)
Ethane can react with chlorine. Explain the free-radical mechanism of this reaction,
including any necessary reaction conditions.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
28EP28
[4]
N15/4/CHEMI/HP2/ENG/TZ0/XX/M
Markscheme
November 2015
Chemistry
Higher level
Paper 2
16 pages
–2–
N15/4/CHEMI/HP2/ENG/TZ0/XX/M
This markscheme is the property of the International Baccalaureate
and must not be reproduced or distributed to any other person
without the authorization of the IB Assessment Centre.
–3–
N15/4/CHEMI/HP2/ENG/TZ0/XX/M
Subject Details: Chemistry HL Paper 2 Markscheme
Mark Allocation
Candidates are required to answer ALL questions in Section A [40 marks] and TWO question in
Section B [2 x 25 marks]. Maximum total = [90 marks].
1.
A markscheme often has more marking points than the total allows. This is intentional.
2.
Each marking point has a separate line and the end is shown by means of a semicolon (;).
3.
An alternative answer or wording is indicated in the markscheme by a slash (/). Either wording can
be accepted.
4.
Words in brackets ( ) in the markscheme are not necessary to gain the mark.
5.
Words that are underlined are essential for the mark.
6.
The order of marking points does not have to be as in the markscheme, unless stated otherwise.
–4–
N15/4/CHEMI/HP2/ENG/TZ0/XX/M
Section A
1.
(a)
(i)
IO3 to I 2 : V/5 to 0;
I  to I 2 :  I/1 to 0;
[2]
Accept change in oxidation number 5 and 1.
Penalize incorrect notation such as 5 or 5 once only.
(ii)
(b)

Oxidizing agent: IO3 /iodate and Reducing agent: I /iodide;
[1]
0.250  2.00  103 / 5.00  104 (mol of KIO3);
(5.00  104  214.00 ) 0.107(g) ;
[2]
Award [2] for the correct final answer.
(c)
(i)
1.4 (%);
Accept 1 (%).
(ii)
systematic;
dilute the orange juice;
Accept other valid suggestions, eg. compare with a standard (showing
colour at equivalence) / look at mixture through a yellow filter / add more
starch (for a sharper colour change) / filter orange juice (through charcoal).
Do not accept repeat titrations or alternative indicator.
(iii)
(d)
1.44  105 (mol) ;
[1]
[2]
[1]
IO3 : 3C6H8O6 / 1:3 mole ratio;
(1.44  105 mol  3 ) 4.32  105 (mol) ;
[2]
Award [2] for the correct final answer.
Award [1 max] for “4.80 x 106 (mol)” obtained from reversed ratio, 3:1.
(e)
(f)
(4.32  105  176.14 ) 7.61 103 (g) ;
Accept Mr  176 and mass  7.60 103(g).
[1]
Ea
/ 1233 (K) ;
R
Accept value from 1200 to 1260 (K).
gradient  
Ea  (1233  8.31 ) 1.02  104 Jmol1 / 10.2kJ mol1
correct Ea value;
correct units;
Allow value in range 9.97  10.5 kJ mol1.
Answer must be given to three significant figures.
Award [3] for correct final answer and units.
Accept J or kJ instead of J mol1 or kJ mol1.
[3]
–5–
2.
(a)
N15/4/CHEMI/HP2/ENG/TZ0/XX/M
(Cu) 1s2 2s2 2p6 3s2 3p6 4s13d10 / 1s2 2s2 2p6 3s2 3p6 3d10 4s1 ;
Do not accept [Ar] 4s13d10.
(Cu2 ) 1s2 2s2 2p6 3s2 3p6 3d9 ;
Do not accept [Ar]
(b)
(c)
3.
4.
[2]
3d9.
(NH3) Lewis base and (Cu2) Lewis acid;
NH3/ligand donates an electron pair (to Cu2) / Cu2 accepts an electron pair
(from NH3);
forming coordinate/dative (covalent) bond;
Accept coordination bond.
Do not accept just covalent bond.
[3]
d orbitals are split (into two sets of different energies);
(frequency/wavelength of visible) light absorbed by electrons moving between d
levels/orbitals;
colour due to remaining frequencies/complementary colour transmitted;
Cu2 has unpaired electrons/partially filled d sub-level / Zn2 has filled d sub-level;
Accept d-d transitions possible between orbitals for M2.
[4]
(a)
C3H8 (g)  5O2 (g)  3CO2 (g)  4H2O(g) ;
Ignore state symbols.
[1]
(b)
bonds broken: 2(CC)/694  8(CH)/3304  5(OO)/2490 / 6488 (kJ);
bonds made: 6(CO)/4476  8(OH)/3712 / 8188 (kJ);
(6488  8188 )  1700 (kJ mol1);
Ignore signs in M1 and M2.
Award [3] for the correct final answer.
Award [2] for 1700 (kJ mol1).
Accept values from 2016 data booklet to give 6494 (kJ) for M1, 8528 (kJ) for M2,
and 2034 (kJ) for M3.
(a)
HOOC (CH2 )4 COOH ;
Accept COOH(CH2)4COOH but not COOH(CH2)4HOOC or HOOC(CH2)4HOOC.
H2N(CH2 )6 NH2 ;
[3]
[2]
Accept NH2(CH2)6NH2 but not H2N(CH2)6H2N or NH2(CH2)6H2N.
Accept full or condensed structural formulas.
(b)
Type: condensation (polymerization);
Structural feature: two functional groups on each monomer;
[2]
Accept —CONH— ;
Accept this group if correctly identified as part of polymer chain.
water/H2O;
[2]
(c)
–6–
5.
(a)
(i)
(ii)
(b)
N15/4/CHEMI/HP2/ENG/TZ0/XX/M
ability of an atom to attract (a pair of) electrons in a covalent bond/molecule
/ ability of an atom to attract a shared pair of electrons;
Do not accept element/nucleus instead of atom.
do not form bonds/compounds / do not share electrons / have (full/stable)
octet / have full/stable outer shell;
Accept (chemically) inert / do not react / stable electron arrangements/
configurations.
[1]
[1]
(Li  Cs) atomic/ionic radius increases;
force of attraction between metal ions and delocalized electrons decreases;
Accept metallic bonding gets weaker.
(F  I ) London/dispersion/instantaneous induced dipole-induced dipole forces
increase;
Accept vdW/van der Waals' forces for London/dispersion forces.
with increasing number of electrons/molar mass/surface area/size of electron
cloud;
Do not accept “with increasing size” or “with increasing mass” only.
(c)
Na has one less energy level/shell compared to Na atom / Na has 2 energy
levels/shells compared to 3 in Na atom;
(compared to Na atom) effective nuclear charge greater in Na (so valence
electrons attracted more strongly to nucleus) / (compared to Na atom) more
protons than electrons in Na (so valence electrons attracted more strongly to
nucleus);
[3 max]
[1 max]
–7–
N15/4/CHEMI/HP2/ENG/TZ0/XX/M
Section B
6.
(a)
(b)
possible to get iron and 3:1 ratio of the two equations;
The ratio may be shown in combining the equations/calculating overall
G/29 (kJ).
possible to get iron and resultant G is negative/29 (kJ);
“Possible to get iron” needs only to be stated once.
Do not accept “possible to get iron” without any reason.
Do not accept “it is not possible to get iron because G is positive”.
(i)
[2]
G Ö  [ 1582  2  10]  [ 742] ;
G Ö   820(kJ mol1 ) ;
Award [2] for the correct final answer.
(ii)
 S
(iii)
G Ö  [ 825.2  (298  ( 0.0236))] ;
Ö
[2]

 [50.9  2 (34.8)]  [87.5  2 (28.3)]   23.6 (JK 1 mol1 ) ;
GÖ   818(kJ mol1 ) / 8.18  105 (J mol1 ) ;
[1]
[2]
Award [2] for the correct final answer.
Award [0] if b(i) is repeated here.
(c)
(i)
Hybridization
NF4 
N2 H2
N2 H 4
sp3;
sp2;
sp3;
[3]
Do not penalize if it is not superscript.
(ii)
sigma bond: overlapping of orbitals end to end/head on / overlapping of
orbitals along internuclear axis;
Accept “axial overlapping of orbitals”.
pi bond: side-ways/parallel overlapping of p orbitals (above and below
internuclear axis);
Accept “overlapping of p orbitals above and below the internuclear axis”.
Accept suitable labelled diagrams.
[2]
–8–
N15/4/CHEMI/HP2/ENG/TZ0/XX/M
(iii)
See saw;
Octahedral;
[4]
Accept any combination of lines, dots or crosses to represent electron
pairs.
Penalize missing lone pairs on fluorine atoms once only.
For SF4 , lone pair on S required for the mark.
Do not allow ECF for a wrong Lewis structure.
Accept saw horse/distorted tetrahedron instead of see-saw.
(d)
(i)
CH3CH2CH3  CH3CHO  CH3CH2OH  CH3COOH ;;
Award [2] for correct order.
Award [1] for CH3COOH  CH3CH2OH  CH3CHO  CH3CH2CH3 as
compounds are not listed in order of increasing boiling point.
Award [1] if one error in the order.
(ii)
CH3CH2CH3 /London/dispersion/instantaneous induced dipole-induced
dipole forces
CH3CHO dipole-dipole forces (and London/dispersion forces)
CH3CH2OH H-bonding (and dipole-dipole and London/dispersion forces)
CH3COOH H-bonding (and dipole-dipole and London/dispersion forces);;
Award [2] for all four correct.
Award [1] for two or three correct.
[2]
H-bonding strongest / London/dispersion forces weakest / dipole-dipole
stronger than London/dispersion / dipole-dipole weaker than H-bonding;
Accept van der Waals’ forces for London/dispersion forces.
CH3COOH forms more/stronger H-bonds than CH3CH2OH / CH3COOH is
more polar than CH3CH2OH;
Accept CH3COOH has more electrons/higher molar mass than CH3CH2OH.
(e)
ionization and (bombardment) by high energy/fast moving electrons/electron gun
(to form positive ions);
acceleration and passing through electric field/potential difference/oppositely
charged plates;
deflection and passing through magnetic field/electromagnet;
Award [1] for naming 3 processes (ionization, acceleration, deflection) in the
correct order with incorrect details.
[4]
[3]
–9–
7.
(a)
(i)
N15/4/CHEMI/HP2/ENG/TZ0/XX/M
Increasing the pressure, at constant temperature:
decreases;
more (gas) molecules/moles on the right / fewer (gas) molecules/moles on
the left;
Increasing the temperature, at constant pressure:
increases;
(forward) reaction is endothermic;
(ii)
(iii)
(iv)
(b)
equilibrium reached faster;
no change in the concentration of reactants/products/yield (at equilibrium) /
position of equilibrium is not affected;
rates of forward and reverse reactions increase (equally);
reduces activation energy;
no change in Kc;
[H2 ]3 [CO]
(K c  )
;
[CH4 ][H2O]
[4]
[3 max]
[1]
(increasing) temperature and (Kc) increases;
Award [0] if both temperature and pressure stated.
[1]
CO (g)  H2 O (g)  H2 (g)  CO 2 (g)
(1.00  x ) (1.00  x )
x
x
x2
K c  10.0 
/ 10.0 
(1.00  x )
x  0.760 / (1.00  x )  0.240 ;
2
x
(1.00  x )
;
[CO]  0.240(moldm3 ) and [H2O] = 0.240(moldm3 ) and [H2 ]  0.760(moldm3 )
3
and [CO2 ]  0.760(moldm ) ;
(c)
[3]
Order with respect to O2: first (order);
Order with respect to NO: second (order);
[2]
(ii)
(rate  ) k [NO]2 [O2 ] ;
[1]
(iii)
172.6 / 173 ;
mol2 dm6 s1 ;
(i)
2
1
Accept M s /mol
[2]
2
L2
1
s .
– 10 –
(iv)
N15/4/CHEMI/HP2/ENG/TZ0/XX/M
NO  NO  N2O 2 (fast);
N2O2 O2 → 2NO2 (slow);
second step is rate determining step;
OR
NO + O2  O + NO2 (fast);
O + NO → NO2 (slow);
second step is rate determining step;
OR
NO + O2 NO3 (fast);
NO3 + NO → 2NO2 (slow);
second step is rate determining step;
Accept single arrow instead of reversible sign.
Accept fast/slow next to the equations.
Do not accept the following mechanisms:
NO + NO  NO2 + N (fast)
N + O2 → NO2 (slow)
OR
NO + NO + O2  N2O4 (slow)
(d)
(e)
N2O 4 → 2NO 2 (fast)
[3]
(i)
Pb  Ni  Fe  Zn;;
Award [2] for the correct order.
Award [1] for Zn  Fe  Ni  Pb as metals not listed in order of increasing
reactivity.
Award [1] if one error in the order.
[2]
(ii)
Pb2/ lead(II) (ions);
Do not accept Pb/lead.
[1]
Dilute sodium chloride:
1
1
H2O(l )  O2 (g)  2H (aq)  2e  / 2OH (aq)  O2 (g)  H2O(l )  2e  ;
2
2
Concentrated sodium chloride:
Cl (aq) 
1
Cl2 (g)  e ;
2
Award [1 max] if equations are given the wrong way round.
Accept e instead of e–.
Ignore state symbols and equilibrium sign.
Accept correct half-equations balanced with different coefficients.
[2]
N15/4/CHEMI/HP2/ENG/TZ0/XX/M
– 11 –
8.
(a)
(i)
base I: 7.0;
base II: 5.5;
[2]
(ii)
base I: strong base and base II: weak base;
[1]
(iii)
NaOH and KOH;
Accept LiOH.
[1]
(iv)

3
3
(from the graph: initial pH  11, pOH  3) [OH ]  10 (mol dm ) ;
103  103 103  103
/
;
0.100  x
0.100
Kb  1.0  105 ;
Kb 
OR
at half-equivalence point, pH  9.0  pKa for base II;
pKb  14.0  9.0  5.0 ;
Award M1 and M2 for stating: “at half-equivalence point pOH  5  pKb for
base II”.
Kb  1.0  105 ;
[3]
Accept other valid methods of working.
Accept a slightly different value of pKb and so Kb if the student uses the pH
at the end point, rather than the initial or half-neutralisation values.
(b)
(v)
methyl red;
Do not accept bromocresol green (since from table 16 data booklet
pH range, 3.8 is too low).
(i)
resists change in pH;
on addition of small amounts of acid and base;
(ii)
[2]
(after mixing) [NH3 ]  [NH4  ] / n NH3  n NH4  / n  4.00  103 mol ;
[OH ]  Kb
[base]
/ pOH  pKb  4.75;
[salt]
pH  9.25;
Award [1 max] if no working shown.
Accept other valid methods of working.
(c)
(i)
[1]
[3]
Reaction A: base and accepts a proton/H;
Accept donates a pair of electrons.
Reaction B: acid and donates a proton/H;
[2]
Award [1] if acid and base identified correctly without a reason.
(ii)
Conjugate acid-base pair 1/2
Conjugate acid-base pair 2/1
Conjugate acid-base pair 1/2
Acid
H2CO3
HCO3
H3O
and
and
and
Base
HCO3;
CO32;
H2O;
[2 max]
– 12 –
(d)
(i)
(ii)
(e)
N15/4/CHEMI/HP2/ENG/TZ0/XX/M
strong acid: (assumed to be) completely/100% dissociated/ionized and
weak acid: partially dissociated/ionized;
Similarity: bubbling/effervescence/gas / heat/increase in temperature / solid
dissolves;
Difference: strong acid more vigorous / faster reaction / greater temperature
increase;
Accept converse statements for weak acid.
(iii)
104(: 1) / 101:105 / 1:104 ;
Do not accept inverse ratio, 1:104.
(i)
Na and Mg: basic
Al: amphoteric
Do not accept amphiprotic.
Si to Cl: acidic
Ar: no oxide ;;
Award [2] for three or four correct, award [1] for two correct.
Award [1] for stating oxides become more acidic towards the right/chlorine
or more basic towards the left/sodium.
Do not penalize incorrect formulas of oxides.
(ii)
[1]
[2]
[1]
[2]
Na2O(s)  H2O(l )  2NaOH(aq) / Na2O(s)  2HCl (aq)  2NaCl (aq)  H2O(l ) ;
Accept a correct equation with any acid or acidic oxide.
SO3 (l)  H2O(l)  H2SO4 (aq) / SO3 (l)  2NaOH (aq)  Na2SO4 (aq)  H2O (l);
Accept a correct equation with any metal hydroxide, metal oxide, metal
carbonate or metal hydrogen carbonate.
Do not accept equation with SO2.
[2]
Ignore state symbols.
Accept ionic equations for M1 and/or M2.
9.
(a)
RBr (l )  NaOH(aq)  ROH(aq)  NaBr (aq) /
RBr (l)  OH (aq)  ROH(aq)  Br (aq) ;
Ignore state symbols.
[1]
(ii)
(1.35  102  7.36  103 ) 6.14  103 / 6.1103 (mol) ;
[1]
(iii)
(molar mass 
(i)
0.842
 )137 (g mol–1);
6.14  10 3
[1]
Accept 138.
(iv)
(137  80  57 which corresponds to C4H9, hence molecular formula)
C4H9Br;
Accept correct structural formula of one of the isomers as molecular
formula.
Do not accept ECF from 9a(iii) for an impossible molecular formula, such
as C4H10Br.
[1]
– 13 –
(v)
N15/4/CHEMI/HP2/ENG/TZ0/XX/M
CH3CH2CH2CH2Br and primary;
(CH3)2CHCH2Br and primary;
CH3CHBrCH2CH3 and secondary;
(CH3)3CBr and tertiary;
If primary, secondary or tertiary not stated, award [3] for four correct, [2] for
three correct and [1] for two correct structural formulas.
Penalize missing hydrogens once only.
Accept either full or condensed structural formulas.
If C5H11Br was used, accept any correct structural formulas.
CH3CH2CH2CH2CH2Br and primary;
(CH3)2CHCH2CH2Br and primary;
CH3CH2CH(CH3)CH2Br and primary;
(CH3)3CCH2Br and primary;
CH3CHBrCH2CH2CH3 and secondary;
CH3CH2CHBrCH2CH3 and secondary;
CH3CHBrCH(CH3)2 and secondary;
CH3CH2C(CH3)2Br and tertiary;
If primary, secondary or tertiary not stated, award [3] for four correct, [2] for
three correct and [1] for two correct structural formulas.
Penalize missing hydrogens once only.
Accept either full or condensed structural formulas.
[4]
– 14 –
(b)
(i)
N15/4/CHEMI/HP2/ENG/TZ0/XX/M
increase in carbon chain;
[1]
(ii)
curly arrow going from lone pair/negative charge on NC– to C;
curly arrow showing Br leaving;
Accept curly arrow either going from bond between C and Br to Br in
1-bromobutane/1-bromo-2-methylpropane or in the transition state.
representation of transition state showing negative charge, square brackets
and partial bonds;
Do not penalize if NC and Br are not at 180° to each other.
Products: CH3CH2CH2CH2CN/(CH3 )2CHCH2CN and Br –/KBr;
[4]
Penalize missing hydrogens and/or incorrect bond linkages (eg CNC
instead of NCC) only once in this question.
Remember to apply ECF from part (a)(v).
(iii)
CH3CH2CH2CH2CN  2H2  CH3CH2CH2CH2CH2NH2
OR
(CH3 )2CHCH2CN  2H2  (CH3 )2CHCH2CH2NH2 ;
Ni / Co / Ru;
Accept Pt/Pd/Cu/Rh.
Accept either chemical symbol or name.
[2]
– 15 –
(c)
N15/4/CHEMI/HP2/ENG/TZ0/XX/M
(i)
HO–
H
H
H
H
H
C
C
C
C
Br
H
H
H
H
H
H
C
+ H2O + Br–
C
H
C2H5
H
CH3
OR
HO–
H
H
H
C
C
CH3
C
C
+ H2O + Br–
H
CH3
Br
CH3
curly arrow going from lone pair/negative charge on O in OH to H on C;
Do not allow curly arrow originating on H in OH.
curly arrow going from CH bond to form CC bond;
curly arrow showing Br leaving;
H2CCHCH2CH3  H2O  Br  / H2CC(CH3)2  H2O  Br;
[4]
Accept NaBr for Br.
Remember to apply ECF from part (a)(v).
Do not penalize if mechanism shown with a secondary bromoalkane.
Do not penalize incorrect side-chain.
Penalize missing hydrogens only once in this question.
(ii)
addition;
CH(C2H5)CH2CH(C2H5)CH2 / C(CH3)2CH2C(CH3)2CH2 ;
Continuation bonds required for the mark.
[2]
– 16 –
(d)
N15/4/CHEMI/HP2/ENG/TZ0/XX/M
Initiation:
UV/ hf / h / heat
Cl2 
 2Cl ;
Reference to UV light or high temperatures must be included.
Propagation:
Cl  C2H6  C2H5   HCl ;
C2H5   Cl2  C2H5Cl  Cl ;
Termination:
Cl  Cl  Cl2 / C2H5   Cl  C2H5Cl / C2H5   C2H5   C4H10 ;
Accept representation of radical without  (eg, Cl, C2H5) if consistent throughout
mechanism.
Accept further chlorination.
Award [3 max] if initiation, propagation and termination are not stated or are
incorrectly labelled for equations.
Accept correct description of processes without equations.
Award [3 max] if Br used correctly instead of Cl.
[4]
M16/4/CHEMI/HPM/ENG/TZ0/XX
Chemistry
Higher level
Paper 1
Thursday 12 May 2016 (morning)
1 hour
Instructions to candidates
• Do not open this examination paper until instructed to do so.
• Answer all the questions.
• For each question, choose the answer you consider to be the best and indicate your choice on
the answer sheet provided.
• The periodic table is provided for reference on page 2 of this examination paper.
• The maximum mark for this examination paper is [40 marks].
16 pages
2216 – 6101
© International Baccalaureate Organization 2016
‡
†
89 ‡
Ac
(227)
56
57 †
72
55
Ba
La
Cs
Hf
132.91 137.33 138.91 178.49
6
88
Ra
(226)
38
Sr
87.62
37
Rb
85.47
5
87
Fr
(223)
73
Ta
180.95
39
Y
88.91
20
Ca
40.08
19
K
39.10
4
7
41
Nb
92.91
40
Zr
91.22
21
Sc
44.96
12
Mg
24.31
11
Na
22.99
3
6
90
Th
232.04
58
Ce
140.12
104
Rf
(267)
22
Ti
47.87
91
Pa
231.04
59
Pr
140.91
105
Db
(268)
23
V
50.94
92
U
238.03
60
Nd
144.24
106
Sg
(269)
74
W
183.84
42
Mo
95.96
24
Cr
52.00
Relative atomic mass
Element
4
Be
9.01
Atomic number
5
3
Li
6.94
4
2
3
1
2
1
H
1.01
1
27
Co
58.93
9
28
Ni
58.69
10
29
Cu
63.55
11
30
Zn
65.38
12
6
C
12.01
14
Si
28.09
32
Ge
72.63
13
Al
26.98
31
Ga
69.72
93
Np
(237)
61
Pm
(145)
107
Bh
(270)
14
5
B
10.81
13
33
As
74.92
15
P
30.97
7
N
14.01
15
34
Se
78.96
16
S
32.07
8
O
16.00
16
10
Ne
20.18
18
Ar
39.95
36
Kr
83.90
17
Cl
35.45
35
Br
79.90
2
He
4.00
18
9
F
19.00
17
109
Mt
(278)
110
Ds
(281)
111
Rg
(281)
112
Cn
(285)
113
Unt
(286)
114
Uug
(289)
115
Uup
(288)
83
Bi
208.98
116
Uuh
(293)
84
Po
(209)
117
Uus
(294)
85
At
(210)
94
Pu
(244)
95
Am
(243)
96
Cm
(247)
97
Bk
(247)
98
Cf
(251)
99
Es
(252)
100
Fm
(257)
101
Md
(258)
102
No
(259)
103
Lr
(262)
66
68
64
62
67
69
65
63
70
71
Dy
Sm
Tm
Tb
Lu
Er
Gd
Ho
Eu
Yb
150.36 151.96 157.25 158.93 162.50 164.93 167.26 168.93 173.05 174.97
108
Hs
(269)
82
Pb
207.2
118
Uuo
(294)
86
Rn
(222)
45
48
54
50
46
44
49
51
47
52
53
In
I
Rh
Cd
Xe
Sn
Pd
Ru
Sb
Ag
Te
101.07 102.91 106.42 107.87 112.41 114.82 118.71 121.76 127.60 126.90 131.29
26
Fe
55.85
8
75
80
78
76
81
79
77
Re
Pt
Os
Tl
Au
Ir
Hg
186.21 190.23 192.22 195.08 196.97 200.59 204.38
43
Tc
(98)
25
Mn
54.94
7
The Periodic Table
–2–
M16/4/CHEMI/HPM/ENG/TZ0/XX
–3–
1.
2.
3.
4.
M16/4/CHEMI/HPM/ENG/TZ0/XX
Which equation represents sublimation?
A.
2Al (s) + 3I2 (g) → 2AlI3 (s)
B.
HgCl2 (s) → HgCl2 (g)
C.
I2 (g) → I2 (s)
D.
CaCO3 (s) + 2HCl (aq) → CaCl2 (aq) + CO2 (g) + H2O (l)
In which mixture is NaOH the limiting reagent?
A.
0.20 mol NaOH + 0.10 mol H2SO4
B.
0.10 mol NaOH + 0.10 mol H2SO4
C.
0.20 mol NaOH + 0.10 mol HNO3
D.
0.10 mol NaOH + 0.10 mol HNO3
Why do gases deviate from the ideal gas law at high pressures?
A.
Molecules have finite volume.
B.
Cohesive forces increase the volume from the ideal.
C.
Increasing pressure increases the temperature of the gas.
D.
Collisions between molecules occur more frequently as pressure increases.
Which is correct for the chromium isotope
A.
24 neutrons and 53 nucleons
B.
24 protons and 29 nucleons
C.
24 protons and 29 neutrons
D.
24 electrons and 53 neutrons
53
24
Cr?
Turn over
–4–
5.
Which electron configuration is correct for the selenide ion, Se2−?
A.
1s2 2s2 2p6 3s2 3p6 4s2 4d10 4p4
B.
1s2 2s2 2p6 3s2 3p6 4s2 4d10 4p6
C.
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p4
D.
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6
The diagram shows the first ionization energies of four consecutive elements in the periodic table.
Which element is in Group 14?
1st ionization energy
6.
M16/4/CHEMI/HPM/ENG/TZ0/XX
C
B
D
A
Increasing atomic number
7.
Which element is a metalloid?
A.
Co
B.
As
C.
Cs
D.
Es
–5–
8.
Which periodic trend is described correctly?
Trend in
9.
10.
11.
M16/4/CHEMI/HPM/ENG/TZ0/XX
Down the group
(top to bottom)
Across the period
(left to right)
A.
atomic radius
increases
increases
B.
ionic radius
decreases
increases
C.
first ionization energy
decreases
decreases
D.
electronegativity
decreases
increases
Which does not affect the colour of the complex ion formed by a particular transition metal?
A.
Oxidation state of the metal
B.
Number of ligands in the complex
C.
Identity of ligands in the complex
D.
Isotope of the metal
Which best explains why transition metal complexes are coloured?
A.
As electrons return to lower energy levels, light of a certain colour is emitted, and the
complementary colour is observed.
B.
As electrons return to lower energy levels, light of a certain colour is emitted, so the complex
appears to have the same colour.
C.
As electrons are promoted to higher energy levels, light of a certain colour is absorbed, and
the complementary colour is observed.
D.
As electrons are promoted to higher energy levels, light of a certain colour is absorbed, so
the complex appears to have the same colour.
Which species breaks the octet rule?
A.
PCl3
B.
BF4−
C.
SCl4
D.
NH4+
Turn over
–6–
12.
13.
Which compound contains both ionic and covalent bonds?
A.
SiH4
B.
NaNO3
C.
H2CO
D.
Na2S
Which of the following are van der Waals’ forces?
I.
II.
III.
14.
15.
M16/4/CHEMI/HPM/ENG/TZ0/XX
Dipole-dipole forces
Hydrogen bonds
London (dispersion) forces
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
In which group do both compounds contain delocalized electrons?
A.
C6H10, C5H10
B.
Na2CO3, NaOH
C.
NaHCO3, C6H6
D.
NaHCO3, C6H12
Which of the following is correct?
Atom
Number of electron
domains
Molecular geometry
Hybridization
A.
C in C2H2
2
linear
sp
B.
C in C2H6
4
square planar
sp3
C.
N in NH3
3
trigonal pyramidal
sp3
D.
O in H2O
4
bent
sp2
–7–
16.
M16/4/CHEMI/HPM/ENG/TZ0/XX
The equation for the formation of ethyne is:
2C (s) + H2 (g) → C2H2 (g)
What is the enthalpy change, in kJ, for this reaction using the enthalpy of combustion data below?
Reaction
C (s) + O2 (g) → CO2 (g)
2H2 (g) + O2 (g) → 2H2O (l)
2C2H2 (g) + 5O2 (g) → 4CO2 (g) + 2H2O (l)
17.
18.
∆H À / kJ
−394
−572
−2602
1
1
(−572) − (−2602)
2
2
A.
2 × (−394) +
B.
2 × (−394) + (−572) − (−2602)
C.
2 × (−394) +
D.
2 × (−394) + (−572) + (−2602)
1
1
(−572) + (−2602)
2
2
Which equation represents the average bond enthalpy of the Si−H bond in SiH4?
A.
SiH4 (g) → SiH3 (g) + H (g)
B.
1
1
SiH4 (g) → Si (g) + H (g)
4
4
C.
SiH4 (g) → SiH3 (g) +
D.
SiH4 (g) → Si (g) + 4H (g)
1
H2 (g)
2
Which transition represents an enthalpy of hydration?
A.
2H2O (l) → H3O+ (aq) + OH− (aq)
B.
NaCl (s) → Na+ (aq) + Cl− (aq)
C.
K+ (s) → K+ (aq)
D.
K+ (g) → K+ (aq)
Turn over
–8–
19.
M16/4/CHEMI/HPM/ENG/TZ0/XX
What are the signs for the entropy changes associated with this reaction?
H2O (g) → H2O (l)
∆Ssystem
A.
+
−
B.
+
+
C.
−
−
D.
−
+
Graph 1 shows a plot of volume of CO2 (g) against time for the reaction of CaCO3 (s) with
1.00 mol dm−3 HCl (aq). The acid is the limiting reagent and entirely covers the lumps of CaCO3 (s).
Which set of conditions is most likely to give the data plotted in graph 2 when the same mass of
CaCO3 (s) is reacted with the same volume of HCl (aq) at the same temperature?
Volume of CO2 (g)
20.
∆Ssurroundings
graph 2
graph 1
Time
Size of lumps
Concentration of acid / mol dm−3
A.
larger
1.00
B.
smaller
0.05
C.
smaller
1.00
D.
larger
0.05
–9–
21.
M16/4/CHEMI/HPM/ENG/TZ0/XX
The data shows the effect of changing reactant concentrations on the rate of the following reaction
at 25 °C.
F2 (g) + 2ClO2 (g) → 2FClO2 (g)
Initial [F2 (g)] /
mol dm−3
Initial [ClO2 (g)] /
mol dm−3
Initial rate of reaction /
mol dm−3 s−1
0.100
0.010
1.20 × 10−3
0.100
0.030
3.60 × 10−3
0.150
0.010
1.80 × 10−3
Which is correct for the order of reaction with respect to the fluorine concentration and the overall
order of reaction?
Order with respect to [F2 (g)]
Overall order
A.
2
1
B.
2
2
C.
1
1
D.
1
2
Turn over
– 10 –
22.
M16/4/CHEMI/HPM/ENG/TZ0/XX
Which pair of graphs represents the same order of reaction?
A.
Concentration
of reactant
Rate
Time
Concentration
of reactant
B.
Concentration
of reactant
Rate
Time
Concentration
of reactant
C.
Concentration
of reactant
Rate
Time
Concentration
of reactant
D.
Concentration
of reactant
Rate
Time
Concentration
of reactant
– 11 –
23.
M16/4/CHEMI/HPM/ENG/TZ0/XX
Which of the terms in the Arrhenius equation takes into account the orientation of the molecules?
- Ea
k = Ae RT
24.
A.
A
B.
Ea
C.
R
D.
T
What is the effect of increasing temperature on the equilibrium?
ClNO2 (g) + NO (g)  ClNO (g) + NO2 (g)
Position of equilibrium
25.
∆H À = −18.4 kJ
Kc
A.
moves to left
decreases
B.
moves to left
no change
C.
moves to right
no change
D.
moves to right
increases
Which is correct for an isolated system in equilibrium?
Gibbs free energy
Entropy
A.
maximum
maximum
B.
maximum
minimum
C.
minimum
maximum
D.
minimum
minimum
Turn over
– 12 –
26.
M16/4/CHEMI/HPM/ENG/TZ0/XX
Which is a conjugate Brønsted–Lowry acid-base pair?
CH3COOH (aq) + H2O (l)  CH3COO− (aq) + H3O+ (aq)
27.
A.
CH3COO− / H3O+
B.
H2O / CH3COO−
C.
H2O / H3O+
D.
CH3COOH / H2O
Aqueous solutions of a weak acid and a strong acid of equal concentration are compared.
Which statements are correct?
28.
I.
II.
III.
The weak acid is less dissociated than the strong acid.
The strong acid reacts with a metal oxide but the weak acid does not.
The strong acid has greater conductivity than the weak acid.
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
The diagram represents the bonding in aluminium chloride.
Cl
Cl
Al
Cl
Cl
Al
Cl
Cl
Which statement is correct?
A.
The aluminium atoms behave as Lewis acids.
B.
The aluminium atoms behave as Lewis bases.
C.
One aluminium atom is a Lewis base and the other a Lewis acid.
D.
One chlorine atom is a Lewis base and the other a Lewis acid.
– 13 –
29.
M16/4/CHEMI/HPM/ENG/TZ0/XX
Which titration curve would occur when a weak acid is added to a strong base?
A.
B.
14
pH 7
14
pH 7
Volume of weak acid
C.
Volume of weak acid
D.
14
pH 7
pH 7
Volume of weak acid
30.
31.
14
Volume of weak acid
Applying IUPAC rules, what is the name of MnO2?
A.
Magnesium(II) oxide
B.
Manganese(II) oxide
C.
Magnesium(IV) oxide
D.
Manganese(IV) oxide
Which statement is correct for a voltaic but not for an electrolytic cell?
A.
An electrolyte is required.
B.
The anode is where oxidation occurs.
C.
Ions move in the electrolyte.
D.
Electrons flow from the negative electrode to the positive electrode.
Turn over
– 14 –
32.
33.
34.
35.
M16/4/CHEMI/HPM/ENG/TZ0/XX
Which compound forms both hydrogen and oxygen at the electrodes when a concentrated
aqueous solution is electrolyzed?
A.
KI
B.
NaCl
C.
H2SO4
D.
AgNO3
z mol of copper is deposited from CuSO4 (aq) by a current, I, in time t. What is the amount of silver,
l
in mol, deposited by electrolysis from AgNO3 (aq) by a current, , in time 2t?
2
z
A.
4
z
B.
2
C.
z
D.
2z
What is the general formula of the alkyne series?
A.
CnH n
B.
CnH2n−2
C.
CnH2n
D.
CnH2n+2
Which statement is correct about the major reaction between 1-chloropropane, CH3CH2CH2Cl,
and dilute sodium hydroxide solution, NaOH (aq)?
A.
The rate equation is second order.
B.
The hydroxide ion acts as a Brønsted–Lowry base.
C.
The reaction has two distinct steps.
D.
Water is a product.
– 15 –
36.
37.
38.
39.
M16/4/CHEMI/HPM/ENG/TZ0/XX
Which molecule can be both reduced by sodium borohydride, NaBH4, and oxidized by warm
acidified potassium dichromate(VI)?
A.
CH3CHOHCH2CH3
B.
(CH3)3CCHO
C.
(CH3)3COH
D.
(CH3)3CCOC(CH3)3
Which molecule contains a chiral carbon?
A.
CH3CHOHCH2CH3
B.
(CH3)3CCHO
C.
(CH3)3COH
D.
(CH3)3COC(CH3)3
A measuring cylinder was used to obtain a known volume of a liquid. The volume was read from
the top of the meniscus and the liquid completely emptied into a flask. The exact same process
was then repeated. Which statement is correct about the overall described procedure and the
volumes measured?
A.
There is a systematic error and the volumes measured are accurate.
B.
There is a random error and the volumes measured are accurate.
C.
There is a random error and the volumes measured are inaccurate.
D.
There is a systematic error and the volumes measured are inaccurate.
Which molecule has an index of hydrogen deficiency (IHD) = 1?
A.
C6 H 6
B.
C2Cl2
C.
C4 H 9 N
D.
C 2H 6O
Turn over
– 16 –
40.
M16/4/CHEMI/HPM/ENG/TZ0/XX
Which analytical technique is used to measure bond lengths in solid compounds?
A.
IR spectroscopy
B.
Mass spectroscopy
C.
NMR spectroscopy
D.
X-ray crystallography
M16/4/CHEMI/HPM/ENG/TZ0/XX/M
Markscheme
May 2016
Chemistry
Higher level
Paper 1
2 pages
–2–
M16/4/CHEMI/HPM/ENG/TZ0/XX/M
1.
B
16.
A
31.
D
46.
–
2.
B
17.
B
32.
C
47.
–
3.
A
18.
D
33.
D
48.
–
4.
C
19.
A
34.
B
49.
–
5.
D
20.
C
35.
A
50.
–
6.
B
21.
D
36.
B
51.
–
7.
B
22.
C
37.
A
52.
–
8.
D
23.
A
38.
D
53.
–
9.
D
24.
A
39.
C
54.
–
10.
C
25.
C
40.
D
55.
–
11.
C
26.
C
41.
–
56.
–
12.
B
27.
B
42.
–
57.
–
13.
B
28.
A
43.
–
58.
–
14.
C
29.
B
44.
–
59.
–
15.
A
30.
D
45.
–
60.
–
M16/4/CHEMI/HP2/ENG/TZ0/XX
Chemistry
Higher level
Paper 2
Thursday 12 May 2016 (morning)
Candidate session number
2 hours 15 minutes
Instructions to candidates







Write your session number in the boxes above.
Do not open this examination paper until instructed to do so.
Answer all questions.
Write your answers in the boxes provided.
A calculator is required for this paper.
A clean copy of the Chemistry data booklet is required for this paper.
The maximum mark for this examination paper is [95 marks].
2216 – 6102
© International Baccalaureate Organization 2016
23 pages
24EP01
–2–
M16/4/CHEMI/HP2/ENG/TZ0/XX
Answer all questions. Write your answers in the boxes provided.
1.
Phosphine (IUPAC name phosphane) is a hydride of phosphorus, with the formula PH3.
(a)
(i)
Draw a Lewis (electron dot) structure of phosphine.
[1]
(ii)
State the hybridization of the phosphorus atom in phosphine.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii)
Deduce, giving your reason, whether phosphine would act as a Lewis acid,
a Lewis base, or neither.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv)
Outline whether you expect the bonds in phosphine to be polar or non-polar,
giving a brief reason.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
24EP02
[1]
–3–
M16/4/CHEMI/HP2/ENG/TZ0/XX
(Question 1 continued)
(v)
Phosphine has a much greater molar mass than ammonia. Explain why
phosphine has a significantly lower boiling point than ammonia.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (vi)
Ammonia acts as a weak Brønsted–Lowry base when dissolved in water.
NH3 (aq) + H2O (l)  NH4+ (aq) + OH− (aq)
Outline what is meant by the terms “weak” and “Brønsted–Lowry base”.
[2]
Weak:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Brønsted–Lowry base:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
Phosphine is usually prepared by heating white phosphorus, one of the allotropes
of phosphorus, with concentrated aqueous sodium hydroxide. The equation for the
reaction is:
P4 (s) + 3OH− (aq) + 3H2O (l) → PH3 (g) + 3H2PO2− (aq)
(i)
The first reagent is written as P4, not 4P. Describe the difference between P4
and 4P.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
24EP03
–4–
M16/4/CHEMI/HP2/ENG/TZ0/XX
(Question 1 continued)
(ii)
The ion H2PO2− is amphiprotic. Outline what is meant by amphiprotic, giving the
formulas of both species it is converted to when it behaves in this manner.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii)
State the oxidation state of phosphorus in P4 and H2PO2–.
[2]
P4:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H2PO2−:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv)
Oxidation is now defined in terms of change of oxidation number. Explore how
earlier definitions of oxidation and reduction may have led to conflicting answers
for the conversion of P4 to H2PO2− and the way in which the use of oxidation
numbers has resolved this.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
24EP04
[3]
–5–
M16/4/CHEMI/HP2/ENG/TZ0/XX
(Question 1 continued)
(c)
2.478 g of white phosphorus was used to make phosphine according to the equation:
P4 (s) + 3OH− (aq) + 3H2O (l) → PH3 (g) + 3H2PO2− (aq)
(i)
Calculate the amount, in mol, of white phosphorus used.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
This phosphorus was reacted with 100.0 cm3 of 5.00 mol dm−3 aqueous sodium
hydroxide. Deduce, showing your working, which was the limiting reagent.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii)
Determine the excess amount, in mol, of the other reagent.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv)
Determine the volume of phosphine, measured in cm3 at standard temperature
and pressure, that was produced.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
24EP05
–6–
M16/4/CHEMI/HP2/ENG/TZ0/XX
(Question 1 continued)
(d)
Impurities cause phosphine to ignite spontaneously in air to form an oxide of
phosphorus and water.
(i)
200.0 g of air was heated by the energy from the complete combustion of
1.00 mol phosphine. Calculate the temperature rise using section 1 of the data
booklet and the data below.
[1]
Standard enthalpy of combustion of phosphine, ∆H Öc = −750 kJ mol−1
Specific heat capacity of air = 1.00 J g−1 K−1 = 1.00 kJ kg−1 K−1
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
The oxide formed in the reaction with air contains 43.6 % phosphorus by mass.
Determine the empirical formula of the oxide, showing your method.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii)
The molar mass of the oxide is approximately 285 g mol−1.
Determine the molecular formula of the oxide.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
24EP06
[1]
–7–
M16/4/CHEMI/HP2/ENG/TZ0/XX
(Question 1 continued)
(iv)
State the equation for the reaction of this oxide of phosphorus with water.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (v)
Suggest why oxides of phosphorus are not major contributors to acid deposition.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (vi)
The levels of sulfur dioxide, a major contributor to acid deposition, can be
minimized by either pre-combustion and post-combustion methods. Outline one
technique of each method.
[2]
Pre-combustion:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Post-combustion:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
24EP07
–8–
2.
M16/4/CHEMI/HP2/ENG/TZ0/XX
Phosgene, COCl2, is usually produced by the reaction between carbon monoxide and
chlorine according to the equation:
CO (g) + Cl2 (g)  COCl2 (g)
(a)
(i)
Deduce the equilibrium constant expression, Kc, for this reaction.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
At exactly 600 °C the value of the equilibrium constant is 0.200. Calculate the
standard Gibbs free energy change, ∆G Ö, for the reaction, in kJ, using sections 1
and 2 of the data booklet. State your answer to three significant figures.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii)
The standard enthalpy change of formation of phosgene, ∆H Öf , is −220.1 kJ mol−1.
Determine the standard enthalpy change, ∆H Ö, for the forward reaction of the
equilibrium, in kJ, using section 12 of the data booklet.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
24EP08
[2]
–9–
M16/4/CHEMI/HP2/ENG/TZ0/XX
(Question 2 continued)
(iv)
Calculate the standard entropy change, ∆S Ö, in J K−1, for the forward reaction at
25ûC, using your answers to (a) (ii) and (a) (iii).
(If you did not obtain an answer to (a) (ii) and/or (a) (iii) use values of +20.0 kJ
and −120.0 kJ respectively, although these are not the correct answers.)
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b)
One important industrial use of phosgene is the production of polyurethanes.
Phosgene is reacted with diamine X, derived from phenylamine.
H2N
(i)
CH2
NH2
X
Classify diamine X as a primary, secondary or tertiary amine.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Phenylamine, C6H5NH2, is produced by the reduction of nitrobenzene, C6H5NO2.
Suggest how this conversion can be carried out.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
24EP09
– 10 –
M16/4/CHEMI/HP2/ENG/TZ0/XX
(Question 2 continued)
(iii)
Nitrobenzene can be obtained by nitrating benzene using a mixture of
concentrated nitric and sulfuric acids. Formulate the equation for the equilibrium
established when these two acids are mixed.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv)
Deduce the mechanism for the nitration of benzene, using curly arrows to
indicate the movement of electron pairs.
(This question continues on the following page)
24EP10
[4]
– 11 –
M16/4/CHEMI/HP2/ENG/TZ0/XX
(Question 2 continued)
(c)
The other monomer used in the production of polyurethane is compound Z shown
below.
H
H
C
O
H
(i)
O
C
H
H
H
State the name, applying IUPAC rules, of compound Z and the class of
compounds to which it belongs.
[2]
Name:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Class:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Deduce the number of signals you would expect to find in the 1H NMR spectrum
of compound Z, giving your reasons.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
24EP11
– 12 –
M16/4/CHEMI/HP2/ENG/TZ0/XX
(Question 2 continued)
The mass spectrum and infrared (IR) spectrum of compound Z are shown below:
Mass spectrum
Relative Intensity
100
80
60
40
20
0
10
15
20
25
30
35
40
45
50
55
60
65
m/z
[Source: http://sdbs.db.aist.go.jp]
IR spectrum
Transmittance / %
100
50
Q
0
4000
3000
2000
1500
Wavenumber / cm−1
[Source: http://sdbs.db.aist.go.jp]
(This question continues on the following page)
24EP12
1000
500
– 13 –
M16/4/CHEMI/HP2/ENG/TZ0/XX
(Question 2 continued)
(iii)
Identify the species causing the large peak at m/z = 31 in the mass spectrum.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv)
Identify the bond that produces the peak labelled Q on the IR spectrum, using
section 26 of the data booklet.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (d)
Phenylamine can act as a weak base. Calculate the pH of a 0.0100 mol dm−3 solution
of phenylamine at 298 K using section 21 of the data booklet.
[4]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
24EP13
– 14 –
3.
M16/4/CHEMI/HP2/ENG/TZ0/XX
The reaction between hydrogen and nitrogen monoxide is thought to proceed by the
mechanism shown below.
(a)
(i)
2NO (g)  N2O2 (g)
fast equilibrium
N2O2 (g) + H2 (g) → N2O (g) + H2O (g)
slow reaction
N2O (g) + H2 (g) → N2 (g) + H2O (g)
fast reaction
State the equation for the overall reaction.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Deduce the rate expression consistent with this mechanism.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii)
Explain how you would attempt to confirm this rate expression, giving the results
you would expect.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
24EP14
[3]
– 15 –
M16/4/CHEMI/HP2/ENG/TZ0/XX
(Question 3 continued)
(iv)
State, giving your reason, whether confirmation of the rate expression would
prove that the mechanism given is correct.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (v)
Suggest how the rate of this reaction could be measured experimentally.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The enthalpy change for the reaction between nitrogen monoxide and hydrogen is
−664 kJ and its activation energy is 63 kJ.
Energy
(b)
Progress of reaction
(i)
Sketch the potential energy profile for the overall reaction, using the axes given,
indicating both the enthalpy of reaction and activation energy.
[2]
(ii)
This reaction is normally carried out using a catalyst. Draw a dotted line labelled
“Catalysed” on the diagram above to indicate the effect of the catalyst.
[1]
(This question continues on the following page)
Turn over
24EP15
– 16 –
M16/4/CHEMI/HP2/ENG/TZ0/XX
(Question 3 continued)
(iii)
Sketch and label a second Maxwell–Boltzmann energy distribution curve
representing the same system but at a higher temperature, Thigher .
[1]
Probability of this energy
Ea
(iv)
Energy
Explain why an increase in temperature increases the rate of this reaction.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
24EP16
[2]
– 17 –
M16/4/CHEMI/HP2/ENG/TZ0/XX
(Question 3 continued)
(c)
One of the intermediates in the reaction between nitrogen monoxide and hydrogen
is dinitrogen monoxide, N2O. This can be represented by the resonance structures
below:
N
(i)
N
N
O
N
O
[3]
Analyse the bonding in dinitrogen monoxide in terms of -bonds and -bonds.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
State what is meant by resonance.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turn over
24EP17
– 18 –
4.
M16/4/CHEMI/HP2/ENG/TZ0/XX
Tin(II) chloride is a white solid that is commonly used as a reducing agent.
(a)
(i)
State why you would expect tin(II) chloride to have a similar lattice enthalpy to
strontium chloride, using section 9 of the data booklet.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Calculate the molar enthalpy change when strontium chloride is dissolved in
water, using sections 18 and 20 of the data booklet.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii)
Tin(II) chloride reacts with water to precipitate the insoluble basic chloride,
Sn(OH)Cl.
SnCl2 (aq) + H2O (l)  Sn (OH)Cl (s) + H+ (aq) + Cl− (aq)
Suggest why tin(II) chloride is usually dissolved in dilute hydrochloric acid.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
24EP18
[1]
– 19 –
M16/4/CHEMI/HP2/ENG/TZ0/XX
(Question 4 continued)
(b)
Tin can also exist in the +4 oxidation state.
Sn4+ (aq) + 2e−  Sn2+ (aq)
E Ö = +0.15 V
Vanadium can be reduced from an oxidation state of +4 to +3 according to the
equation:
VO2+ (aq) + 2H+ (aq) + e−  V3+ (aq) + H2O (l)
(i)
E Ö = +0.34 V
Calculate the cell potential, E Ö, and the standard free energy, ∆G Ö, change for
the reaction between the VO2+ and Sn2+ ions, using sections 1 and 2 of the data
booklet.
[2]
E Ö:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ∆G Ö:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Deduce, giving your reason, whether a reaction between Sn2+ (aq) and VO2+ (aq)
would be spontaneous.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (c)
Outline, giving the full electron configuration of the vanadium atom, what is meant by
the term transition metal.
[2]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (This question continues on the following page)
Turn over
24EP19
– 20 –
M16/4/CHEMI/HP2/ENG/TZ0/XX
(Question 4 continued)
(d)
In an aqueous solution of vanadium(III) chloride, the vanadium exists as [V (H2O)6]3+,
[VCl (H2O)5]2+ or [VCl2 (H2O)4]+ depending on the concentration of chloride ions in the
solution.
(i)
Describe how Cl− and H2O bond to the vanadium ion.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (ii)
Outline what would happen to the wavelength at which the vanadium complex
ions would absorb light as the water molecules are gradually replaced by chloride
ions, using section 15 of the data booklet.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (e)
Eight successive ionisation energies of vanadium are shown in the graph below:
18000
16000
14000
I.E.
/
kJ mol−1
12000
10000
8000
6000
4000
2000
0
1
2
3
4
5
6
Number of electrons removed
(This question continues on the following page)
24EP20
7
8
[2]
– 21 –
M16/4/CHEMI/HP2/ENG/TZ0/XX
(Question 4 continued)
(i)
State the sub-levels from which each of the first four electrons are lost.
First: . . . . .
(ii)
Second: . . . . .
Third: . . . . .
[1]
Fourth: . . . . .
Outline why there is an increase in ionization energy from electron 3 to
electron 5.
[1]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iii)
Explain why there is a large increase in the ionization energy between electrons 5
and 6.
[3]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv)
Vanadium is comprised almost entirely of 51 V. State the number of neutrons an
atom of 51 V has in its nucl