TUTORIAL : MATTER
______________________________________________________________________________
1
(a) An atom X is twice as heavy as one carbon –12 atom. Calculate the relative atomic
mass of element X.
(b) The relative atomic mass of element Y is 32. Calculate the mass of one atom of Y in
gram.
2 (a) Chlorine isotopes occur naturally as 35Cl and 37Cl. The ratio of the relative abundance of
these two isotopes is : 35Cl = 3.127
37
Cl
12
Based on the scale of C = 12.00, the relative mass of 35Cl and 37Cl are 34.9689 a.m.u.
and 36.9659 a.m.u. respectively. Calculate the relative atomic mass of chlorine.
(b) The following is the mass spectrum of zirconium. Calculate the relative atomic mass of
zirconium.
52
%
intensity
14
13
93
94
12
9
90
3
(a)
(b)
4
91
92
mass (a.m.u)
Define :
i.
Isotope
ii.
Proton number
iii.
Nucleon number
The element of iron consists of 5.82% 54Fe, 91.66% 56Fe, 2.19% 57Fe and 0.33%
58
Fe.The isotopic mass of these four isotopes are 53.9396, 55.9394, 56.9354 and
57.9333 respectively. Calculate the relative atomic mass of iron.
(a)
Explain the process of determining atomic mass using the mass spectrometer.
(b)
The isotopes of Ag occur naturally as 107Ag and 109Ag with their atomic mass of
106.906 a.m.u and 108.868 a.m.u respectively. If the relative atomic mass of Ag is
107.868, what would be the percentage relative abundance of these two isotopes?
1
5
(a)
Referring to the periodic table;
i.
what are the sub atomic particles that make up the following elements:
silicon-28, chlorine-37 and bromine-79.
ii.
identify the species A, B, C and D.
Number of
Species
b)
protons
neutrons
electrons
A
1
0
2
B
1
1
0
C
9
10
10
D
2
2
2
The element Mg consists of three isotopes which are 24Mg, 25Mg and 26Mg.
The relative atomic mass of Mg is 24.3.
6
i.
Which is the most abundant isotopes of Mg?
ii.
State the number of protons and the number of neutrons of this isotope.
(a) A sample of oxygen which contains 2 isotopes with nucleon number 16 and 18, is
analyzed in a mass spectrometer. How many peaks would be expected in the mass
spectrum of oxygen? Explain your answer.
(b) Determine the molecular formula of compound A, which has an empirical formula CH2O
and its relative molecular mass is 90 g mol-1.
7
8
Calculate the relative molecular mass of each of the following compounds
i.
glucose, C6H2O6
ii.
copper (II) sulphate, CuSO4
iii.
magnesium oxide, MgO
Calculate :
i.
the number of atoms in 5 g of Ag
ii.
the number of molecules in 25 g of methane, CH4
2
iii.
9
10
the number of carbon atoms in 0.5 mol of ethane, C2H4.
Quinine C20H24N2O2, is a compound extracted from cinchona tree which is
traditionally used to treat malaria. If given 1.08 g of quinine sample, calculate:
i.
molecular weight of quinine,
ii.
the number of moles of quinine,
iii.
the number of molecules of quinine,
iv.
the number of hydrogen atoms,
v.
the mass of carbon atoms in grams.
72 cm3 sample of NH3 gas is allowed to react with oxygen at room temperature and 1 atm
according to the equation:
4NH3 (g) + 5O2 (g)
4NO(g) + 6H2O (l)
Calculate the number of molecules of water produced.
11
12
Determine the oxidation number of the underlined elements in the following compounds
i.
NO2
iv.
H2SO4
ii.
KMnO4
v.
Cr2O72-
iii.
HClO3
vi.
I O3-
Balance each of the following equation
i.
NaOH (aq) + FeCl3 (s)
Fe(OH)3 (s) + NaCl (aq)
ii.
C4H10 (g) + O2 (g)
CO2 (g) + H2O (l)
iii.
Fe (s) +H2O (l)
Fe3O4 (s) + H2 (g)
iv.
Fe2O3 (s) +HCl (aq)
FeCl3 (aq) +H2O (l)
v.
Cr(OH)3 (aq) + IO 3 - (aq)
CrO 3 2 - (aq) + I- (aq)
vi.
Cl2 (aq)
ClO4- (aq) + Cl- (aq) (basic)
3
(acidic)
TUTORIAL 2 : ATOMIC STRUCTURE
______________________________________________________________________________
1
(a)
(b)
(c)
What is the difference between continuous spectrum and line spectrum?
Explain the difference between ground state and excited state.
Briefly describe Bohr’s theory of the hydrogen atom.
2
(a)
(b)
Explain why the emission spectrum of hydrogen atom is a line spectrum?
How is the second line of Brackett series produced?
3
The first line of Balmer series has a wavelength of 656.3 nm. Calculate the energy
difference between the two energy levels that produced this line?
4
When an electron makes a transition from higher energy level to lower energy level, a
photon with the frequency of 6.6 x 1015 Hz Is emitted. Calculate:
(a)
the wavelength of the photon.
(b)
energy for 1 mole of electron for the above transitions.
(c)
What is the energy and wavelength of a photon emitted during a transition from
the fifth energy level to the second energy level?
(d)
Describe de Broglie’s postulates and Heisenberg’s uncertainty principle.
5
State the maximum electrons that can be occupy an orbital with the following quantum
numbers:
(a)
6
(b)
n=3, l=2
(c)
n=5, l=1
Which of the following quantum numbers are allowed? Explain your answer.
(a)
(c)
7
n=2, l =0, s =-1/2
(1, 1, 0, +1/2)
(2, 1, 0, +1/2)
(b)
(d)
(3, 1, -2, +1/2)
(2, 0, 0, +1)
(a)
State Aufbau’s principle.
(b)
Arrange the following orbitals according to increasing energy level.
4dxy, 3dxy, 3dyz, 4pz, 3pz, 3py, 2py, 3s, 2s, 1s
8
Give one set of possible quantum number for one electron in the following orbital.
(a) 1s
9
(b) 2s
(c) 3p
(d) 3d
Give the expected ground state electron configuration for atoms with the
following atomic numbers:
4
(a)
10
Z=55
(b)
Z=40
(c) Z=62
(a)
State Hund’s rule and Pauli’s exclusion principle.
(b)
Write the electronic configurations for Al, K, Cr and Cu. Explain the anomalous
electron configuration in chromium and copper.
(c)
Atom X has 5 electrons.
i.
Write the electronic configuration for X.
ii.
Give a set of quantum numbers for each of valence electrons.
5
TUTORIAL 3: PERIODIC TABLE
1
2
The table below shows the group and period of the elements P, Q, R, S and T.
Element
Period
Group
P
2
15
Q
2
18
R
3
1
S
4
17
T
4
16
(a)
Write the electronic configuration for each of the element
(b)
Write the electronic configuration for P 3- , R + and S - .
(c)
State the block (s, p or d) for each element
State the period, group and block for each element below
A : 1s2 2s2 2p6 3s2 3p6
B : 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p5
C : 1s2 2s2 2p6 3s2 3p6 4s2
3
4
Element Y has electronic configuration of 1s2 2s2 2p6 3s2 3p5.
(a)
State the number of valence electron.
(b)
Determine the main oxidation number.
(c)
Identify element Y.
The first six ionization energies of element X are shown below:
Ionization
Energy (kJ / mol)
IE1
IE2
IE3
IE4
IE5
IE6
760
1540
6300
8399
9950
11900
Determine the group for element X.
5
The table below shows the electronic configuration of elements W, X, Y and Z
Elements
W
Electronic configuration
[Ne]3s1
6
(a)
(b)
(c)
6
X
[Ne] 3s23p4
Y
[Ar]4s2
Z
[Ar]3d104s24p4
Explain
i.
the difference in the first ionization energy between element W and X
ii.
the difference in ionic radius between X 2- and Y 2+
Among elements X, Y and Z, which has
i.
the lowest electron affinity?
ii.
the highest oxidizing ability?
Write the molecular formula of the substance formed when Y reacts with oxygen.
How does the substance behave in aqueous solution?
The graph below shows the variation of ionization energies for element Z.
log ionization energy
number of electrons removed
6
(a)
State the group and period for element Z.
(b)
Name element Z.
(c)
Why does it need a higher energy to remove the fourth electron?
(d)
Explain how does the atomic radius of Z change when an electron is removed.
(e)
State the change of atomic radius of Z when an electron is added.
7
(f)
State the oxidation number of element Z.
TUTORIAL 4: CHEMICAL BONDING
1
Complete the table below :
Group
Valence
electron
Lewis
dot symbol
1
2
13
14
15
16
17
18
Na
Mg
Al
Si
P
S
Cl
Ne
2
(a)
(b)
(c)
State the electronic configuration for the cations of the following element :
Al : 1s22s22p63s23p1
Fe : 1s22s22p63s23p64s23d6
Cu : 1s22s22p63s23p64s23d10
3
State the electronic configuration for the anions of the following element :
(a)
(b)
(c)
F : 1s22s22p5
N : 1s22s22p3
S : 1s22s22p63s23p
4
Show the formation of MgBr2 using Lewis structures.
5
Describe and draw the geometry of the species in which around the central atom there are,
(a)
Four single bonds, two unshared pairs of electrons.
(b)
Five single bonds.
(c)
Two single bonds, one unshared pair of electrons.
(d)
Three single bonds, two unshared pairs of electrons.
(e)
Two single bonds, two unshared pairs of electrons.
(f)
Five single bonds, one unshared pair of electrons.
6
Antimony pentafluoride, SbF5 , reacts with XeF4 and XeF6 to form ionic compounds
XeF3+, SbF6- and XeF5+. Describe the geometries of the cations and the anion in these two
compounds.
7
List the following molecules in order of increasing dipole moment :
CF3Cl , CF4 , CF2Cl2 , CF2H2 , CH4
8
(a)
Define dipole moment.
(b)
How is it possible for a molecule to have polar bond and yet be non-polar?
8
TUTORIAL 5: CHEMICAL EQUILIBRIUM
___________________________________________________________________________
1
Write the equilibrium law for each of the following reactions in terms of molar
concentrations:
2
(a)
2PCl3(g) + O2 (g)
2 POCl3 (g)
(b)
2SO3(g)
(c)
N2H4 (g) + 2O2 (g)
2NO (g) + 2H2O (g)
(d)
N2H4 (g) + 6H2O2 (g)
2NO2 (g) + 8H2O (g)
(e)
SOCl2 (g)
2SO2 (g) + O2 (g)
+
H2O (g)
SO2 (g) + 2 HCl (g)
Write the equilibrium law for each of the following gaseous reactions in terms of molar
concentrations:
3
(a)
3Cl2 (g)
+ NH3 (g)
NCl3 (g) + 3HCl (g)
(b)
PCl3 (g)
+ PBr3 (g)
PCl2Br (g) + PClBr2 (g)
(c)
NO (g) + NO2 (g) + H2O (g)
(d)
H2O (g) + Cl2O (g)
e)
Br2(g) + 5F2 (g)
2HNO2 (g)
2HOCl (g)
2 BrF5 (g)
For chemical equation,
2SO2 (g) + O2 (g)
2 SO3 (g)
what is Kc for this equilibrium at 25 oC if Kp = 3 x 1025 atm-1
4
At a certain temperature, Kc = 4.50 for the reaction
N2O4 (g)
2NO2 (g)
If 0.300 mol of N2O4 is placed into a 2.00 L container at this temperature, what will be
the equilibrium concentrations of both gases?
5
Consider this system at equilibrium:
9
4NH3(g) + 3O2(g)
6
2N2(g) + 6H2O(g)
H= -1531 kJ
(a)
Is the reaction exothermic or endothermic?
(b)
If the state of equilibrium of the system is disturbed by the addition of O2 , in
which direction, left or right, must the reaction occur to reestablish equilibrium?
(c)
If the state of equilibrium of the system is disturbed by the addition of N 2, in
which direction, left or right, must the reaction occur to reestablish equilibrium?
(d)
If the state of equilibrium of the system is disturbed by the additional of heat , in
which direction will the reaction occur, left or right, to reestablish equilibrium?
For the following equations, predict in which direction, left or right, the equilibrium will
shift when each these changes are made, that is increase in temperature, increase in
pressure by decreasing the volume of the reaction vessel, and addition of a catalyst :
2SO3(g)
4NH3(g)
OF2(g)
2SO2(g) + O2(g)
+ 3O2(g)
2N2(g) + 6H2O(g)
+ H2O(g)
O2(g)
10
+ 2HF(g)
ΔH = +197 kJ
ΔH = - 1531 kJ
ΔH = - 318 kJ
TUTORIAL 6: IONIC EQUILIBRIA
_____________________________________________________________________________
1
2
Identify Lewis acid and Lewis base in each of the following reactions:
(a)
SnCl4(s) + 2Cl-(aq)
(b)
Hg2+(aq) + 4CN-(aq)
SnCl62-(aq)
Hg(CN)42-(aq)
Classify each of the following species as a Bronsted acid, base or both:
H2O, OH-, H3O+, NH3, NH4+, NH2-, CO32-, HBr, HCN
3
Identify the acid-base conjugate pairs in each of the following reactions:
(a)
CH3COO- + HCN
CH3COOH + CN-
(b)
HCO3- + HCO3-
H2CO3 + CO32-
(c)
H2PO4- +
HPO42- + NH4+
NH3
4
The concentration of OH- in a certain household ammonia cleaning solution is 0.0025 M.
Calculate the concentration of H+ ions.
5
Indicate whether the following solutions are acidic, basic or neutral:
(a)
0.62 M NaOH
(b)
1.4 x 10-3 M HCl
(c)
2.5 x 10-11 M H+
(d)
3.3 x 10-10 M OH-
6
The concentration of H+ ions in a bottle of vinegar was 3.2 x 10-4 M right after the cork
was removed. Only half of the vinegar was consumed. The other half, after it had been
open in the air for a month, was found to have a hydrogen ion concentration of 1.0 x 10 -3
M. Calculate the pH of the vineger on these two occasion.
7
The solubility of silver sulphate is 1.5 x 10-2 mol/L. Calculate the solubility product of the
salt
8
It was found experimentally that the solubility of calcium sulphate is 0.67 g/L. Calculate
the Ksp for calcium sulphate.
11
9
Will precipitate form if 200 mL of 0.0040 M BaCl2 are added to 600 mL of 0.0080 M
K2SO4? ( Ksp BaSO4= 1.1 x 10-10 )
TUTORIAL: PHASE EQUILIBRIUM
_________________________________________________________________________
1
i.
ii.
Define the following terms :
Phase
Component
2.
State the number of phases and components for each of the system given
in the table below :
System
mixture of O2, N2 and CO2 gases
mixture of ethanol and water
immiscible solution of benzene
and water
HNO3(aq) which is in an
equilibrium with its vapour
Number of Phases
Number of Components
3
Substance X has its triple point at 18 ○C and 0.5 atm. The melting point and
boiling point are 20 ○C and 300 ○C respectively. Sketch the phase diagram for X.
4
Xenon is a noble gas. The melting point and boiling point for xenon are -112 ○C
and -107 ○C respectively. The triple point of xenon is at -121 ○C and 282 torr whereas the
critical point is at 16.6 ○C with a pressure of 57.6 atm.
(a)
Sketch and label a phase diagram for xenon.
(b)
Compare the density of xenon in liquid and solid phases.
5
Figure below shows the phase diagram for water.
P
C
A
◘H
◘F
◘E
◘G
B
D
T
Fig. 7.1
(a)
Which curve represent the equilibrium of ice and water vapour?
12
(b)
State the phase changes when a sample at point E is heated at constant pressure
until point F is reached.
(c)
Name the point which the BC line intersects with 1 atm line
13