CH1120 Summer 2005
June 27, 2005
Preliminary Exam
Name:_______________________________
Score:____/100
1. (4 pts) Write and balance an equation for the reaction of aqueous aluminum
sulfate with aqueous sodium hydroxide to form solid aluminum hydroxide and
aqueous sodium sulfate.
Al2(SO4)3(aq) + 6NaOH(aq)
2Al(OH)3(s) + 3 Na2 SO4(aq)
2. Magnesium nitride can be formed by the reaction of magnesium metal with
nitrogen gas. The balanced reaction is:
3Mg(s) + N2(g)
Mg3N2(s)
(4 pts) How many grams of magnesium nitride can be made in the reaction of
35.00g of magnesium and 15.00g of nitrogen?
48.43 g magnesium nitride
3. (6 pts) Name each of the following compounds:
a. K2Cr2O7
potassium dichromate
CH1120 Summer 2005
June 27, 2005
b. SiS2
silicon disulfide
c. H2SO3
sulfurous acid
4. (6 pts) Write balanced molecular, ionic, and net ionic equations for the reaction
between strontium nitrate, Sr(NO3)2, and sodium sulfate, Na2SO4. Show all state
symbols.
a. Molecular:
Sr(NO3)2(aq) + Na2SO4(aq)
SrSO4(s) + 2NaNO3(aq)
b. Ionic:
Sr2+ + 2NO3- + 2Na+ + SO42-
SrSO4(s) + 2Na+ + 2NO3-
c. Net-Ionic:
Sr2+ + SO42-
SrSO4(s)
5. (4 pts) What is the [H3O+] in lemonade, which has a pH of 2.91?
1.23x10-3
CH1120 Summer 2005
June 27, 2005
6. (8 pts) Write the full and valence electron configurations for each of the following
elements.
a. sulfur
1s2 2s2 2p6 3s2 3p4
Full:
Valence:
3s2 3p4
b. Copper
1s2 2s2 2p6 3s2 3p6 4s1 3d10
Full:
Valence:
4s1 3d10
7. (8 pts) Write correct Lewis structures for each of the following, showing all bonds
and non-bonding electrons:
a. CO2
O
C
O
b. SO32-
2-
O
O
S
O
CH1120 Summer 2005
June 27, 2005
8. (4 pts) Use the following information, and the Gibbs equation to determine the
temperature at which the reaction becomes spontaneous:
2NO(g) + O2(g)
2NO2(g)
H° = -114.1 kJ
S° = -146.2 JK-1
780 K
9. (4 pts) Aerosol containers carry warnings that they should not be heated.
Suppose you have an aerosol container filled with a flammable gas at 2.50 atm
and 22°C. This canister will explode when the internal pressure exceeds 8.0
atm. At what temperature will this occur?
944 K
10. (6 pts) Arrange the following substances in expected order of increasing boiling
point and explain the position of each one in terms of their intermolecular forces:
H2O, NH3, CH4, CH3CH3.
CH4<CH3CH3<NH3<H2O
Methane and ethane are nonpolar molecules that are held together only by Van
der Waal’s forces or London Dispersion forces. These are very weak
intermolecular forces, so these have low boiling points. Ethane has a higher
boiling point because it is a larger molecule. Ammonia and water are polar
molecules that have dipole-dipole interactions holding them together, as well as
hydrogen bonding. These are much stronger forces. Water is more polar than
ammonia and has stronger intermolecular forces, so it boils at a higher
temperature.
CH1120 Summer 2005
June 27, 2005
11. (12 pts) How much energy does it take to convert 250.0g of ice at -25°C to steam
at 150°C?
Specific heat capacities: ice, 2.1 J g-1 °C-1; liquid, 4.2 J g-1 °C-1; steam 2.1 J g-1 °C1
;
Hvap = 40.7 kJ mol-1; Hfus = 6.02 kJ mol-1. Show each step clearly for full credit.
793 kJ
12. (12pts) An aqueous solution of ethylene glycol used as an automobile engine
coolant is 40.0% HOCH2CH2OH by mass and has a density of 1.05g/mL. What
are (a) molarity, (b) molality, and (c) mole fraction of HOCH2CH2OH in this
solution?
a. 6.77 M
b. 10.8 m
c. 0.162
CH1120 Summer 2005
June 27, 2005
13. (6pts) Sorbitol is a sweet substance found in fruits and berries and sometimes
used as a sugar substitute. An aqueous solution containing 1.00g sorbitol in
100.0g water is found to have a freezing point of -0.102°C. Kf (H2O) = 1.86°C m1
. Calculate the molar mass of sorbitol.
182 g/mol
3C + 2D
14. (8 pts) Consider the hypothetical reaction: A + 2B
Suppose that at one point in the reaction, [A] = 0.4658M, and 125s later [A] =
0.4282M. During this time period:
(a) What is the average rate of reaction expressed in Ms-1?
3.01x10-4
(b) What is the rate of formation of C, expressed in Ms-1?
9.03x10-4
CH1120 Summer 2005
June 27, 2005
2NOCl(g) data was collected for the
15. (8 pts) For the reaction 2NO(g) + Cl2(g)
initial rate of reaction as a function of reactant concentration.
Experiment
1
2
3
Initial [NO]
0.0125 M
0.0125 M
0.0250 M
Initial [Cl2]
0.0255 M
0.0510 M
0.0255 M
Initial Rate
2.27 x 10-5 Ms-1
4.55 x 10-5 Ms-1
9.08 x 10-5 Ms-1
a. What is the rate law for this reaction?
r = k[NO]2[Cl2]
b. Calculate the initial rate for a reaction in which [NO] = 0.100M and [Cl2] =
0.100M
5.70x10-3 M/s
CH1120 Summer 2005
June 27, 2005
1A
1
8A
18
1
H
1.01
2A
2
3A
13
4A
14
5A
15
6A
16
7A
17
2
He
4.00
3
Li
6.94
4
Be
9.01
5
B
10.8
6
C
12.0
7
N
14.0
8
O
16.0
9
F
19.0
11
Na
23.0
19
K
39.1
12
Mg
24.3
3B
3
4B
4
5B
5
6B
6
7B
7
14
Si
28.1
15
P
31.0
16
S
32.1
17
Cl
35.4
10
Ne
20.2
18
Ar
39.9
37
Rb
85.5
20
Ca
40.1
38
Sr
87.6
21
Sc
45.0
39
Y
88.9
22
Ti
47.9
40
Zr
91.2
23
V
50.9
41
Nb
92.9
24
Cr
52.0
42
Mo
95.9
32
Ge
72.6
50
Sn
119
33
As
74.9
51
Sb
122
34
Se
79.0
52
Te
128
55
Cs
133
87
Fr
(223)
56
Ba
137
88
Ra
226
57
La
139
89
Ac
227
72
Hf
178
104
Rf
(261)
73
Ta
181
105
Ha
(262)
86
Rn
(222)
71
Lu
175
103
Lr
(260)
8B
Lanthanides
Actinides
8
9
10
1B
11
2B
12
25
Mn
54.9
43
Tc
(98)
26
Fe
55.8
28
Ni
58.7
29
Cu
63.5
44
Ru
101
27
Co
58.9
45
Rh
103
47
Ag
108
74
W
184
106
Unh
(263)
75
Re
186
107
Uns
(262)
76
Os
190
108
Uno
(265)
77
Ir
192
109
Une
(266)
46
Pd
106
78
Pt
195
30
Zn
65.4
48
Cd
112
13
Al
27.0
31
Ga
69.7
49
In
115
79
Au
197
80
Hg
201
81
Tl
204
82
Pb
207
83
Bi
209
84
Po
(209)
35
Br
79.9
53
I
127
85
At
(210)
58
Ce
140
59
Pr
141
90
Th
232
91
Pa
231
60
Nd
144
92
U
238
61
Pm
(145)
93
Np
(237)
62
Sm
150
94
Pu
(244)
63
Eu
152
95
Am
(243)
64
Gd
157
96
Cm
(247)
65
Tb
159
97
Bk
(247)
66
Dy
162
98
Cf
(251)
67
Ho
165
99
Es
(252)
68
Er
167
100
Fm
(257)
69
Tm
169
101
Md
(258)
70
Yb
173
102
No
(259)
Reactions become spontaneous under the same free energy conditions as a phase
change.
R = 0.0821 L atm K-1 mol-1
1 atm = 760 torr
1 atm = 101.325 kPa
1 atm = 760 mmHg
36
Kr
83.8
54
Xe
131
CH1120 Summer 2005
∆H reaction = ∆H products − ∆H reactants
∆Sreaction = ∆Sproducts − ∆Sreactants
∆Greaction = ∆Gproducts − ∆Greactants
∆G° = ∆H° − T∆S°
P1V1 P2V2
=
T1
T2
PV = nRT
mass
m
=
molar mass M
mass
d=
volume
∆T = K f m
n=
∆T = K b m
Π = MRT
Rate =
ln
[A] final − [A]initial
∆t
[A]t
= −kt
[A]0
o
Psolv = χ solv Psolv
June 27, 2005