1. Ethylene glycol, the major ingredient in antifreezes at -11.5˚C. What is the freezing
point in (a) K, (b) ˚F. (10%)
K = ˚C + 273.15
˚F =
5
˚C + 32˚
9
-11.5˚C = 261.65 K = 11.3 ˚F
2. Draw a modern periodic table including the atomic symbols for the elements with
atomic numbers 1-20, and all the alkali metals, alkali earth metals, halogens, nobel
gases, and 3 d transition metals. (20%)
3. A cube of gold that is 1.00 cm on a side has a mass of 19.3 g. A single gold atom
has a mass of 197.0 amu. (a) How many gols atoms are in the cube ? (5%) (b)
What is the density of gold? (5%) (c) From the information given, estimate the
diameter in Å of a single gold atom. (5%)
(a)
19.3 g
22
= 5.90 x 10 Au atoms
-24
197.0 amu x1.66 x 10 g
(b) D =
(c)
3
M
19.3 g
3
=
= 19.3 g/cm
3
V
1 cm
5.9 x 10 22 = 3.89 x 107 Au atoms,
1 cm
= 2.57 x 10-8 cm = 2.57 Å
7
3.89 x 10
4. Determine which of the following compounds are soluble in water: (i) PbNO3 (ii)
CaCl2 (iii) BaSO4 (iv) CuCO3 (v) Ag(C2H3O2) (10%)
(i) PbNO3 (ii) CaCl2 (v) Ag(C2H3O2)
5. Write the balanced equations for the following reactions (20%)
(i) gold dissolved in aqua regia
Au(s) + NO3-(aq) + 4H+(aq) + 4Cl-(aq) → AuCl4-(aq) + 2H2O(l) + NO(g)
(ii) complete combustion of propane
C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(g)
(iii) the action Alka-Seltzer with stomach acid
NaHCO3(aq) + HCl(aq) → NaCl(aq) + H2O(l) + CO2(g)
(iv) Nickel metal with hydrochloric acid.
Ni(s) + 2HCl(aq) → NiCl2(aq) + H2(g)
6. (a) What is the first law of thermodynamics? (b) Why is the enthalpy change equal
to the heat gained by the system at constant pressure when only P-V work is
involved? (10%)
(a) Energy is conserved. Any energy that is lost by the system must be gained by
the surroundings, and vice versa.
∆E = q + w
E : internal energy
q: when heat is transferred to the system from the surrounding, q has a positive
value
w : when work is done in the system by the surroundings, w has a positive value
(b) When a change occurs at constant pressure, the change in enthalpy, ∆H. Is
given by the following relationship:
∆H = ∆ (E+ PV)
= ∆E + P∆V
(The work involved in the expansion or compression of gases is w = -P∆V)
∴ ∆H = ∆ (E+ PV)
= (qP + w) – w = qP
7. (a) What is Hess’s Law? (5%) (b) What is the enthalpy of formation?(5%) (c)
Calculate ∆H for the reaction C2H4(g) + 6F2(g) → 2CF4(g) + 4 HF(g) (5%)
(a) If a reaction is carried out in a series of steps, ∆H for the overall reaction
will equal the sum of the enthalpy changes for the individual steps.
(b) Enthalpy of formation is the enthalpy change that occurs when a compound is
formed from its component elements.
(c) ∆H = (1) x 2 + (2) x 2 + (3) x (-1)
= (-537 kJ) x 2 + (-680 kJ) x 2 + (-52.3 kJ) x (-1)
= -2381.7 kJ
8. (a) Calculate the ionization energy of the ground-state hydrogen atom (in
kJ/mol) (5%) (b) Calculate the wavelengths (in nm) of the first three lines in
the Balmer series. (10%)
1
1
(a) ∆E = (-hcRH) (
- 2 )
2
nf ni
= (-2.18 x 10-18 J) (
1 1
)
∞ 12
3
= 2.18 x 10-18 J = 1.31 x 10 kJ/mol
(b) Balmer series : n1 = 2, n2 = 3, 4, 5 ……
(i) ni = 3, nf = 2
(6.63 x 10 -34 J - s) (3.00 x 10 8 m )
hc
s = 6.56 x 10-7 m = 656 nm
=
λ=
1
1
∆E
- (-2.18 x 10 -18 J) ( 2 - 2 )
2 3
(ii) ni = 4, nf = 2
λ=
hc
= 4.86 x 10-7 m = 486 nm
∆E
(iii) ni = 5, nf = 2
λ=
hc
= 4.34 x 10-7 m = 434 nm
∆E
9. Use the de Broglie relationship to determine the wavelengths (in m) if the
following objects: (a) an 85-kg person skiing at 50 km/hr, (b) a 10.0-g bullet
fired at 250 m/s, (c) a lithium atom moving at 2.5 x 105 m/s (10%)
(a) λ=
h
6.63 x 10 -34 J - s
-37
=
= 5.6 x 10 m
m
mv 85 kg x 13.89
s
(b) λ=
h
6.63 x 10 -34 J - s
-34
=
= 2.65 x 10 m
-3
mv 10 x 10 kg x 250 m
s
(c) λ=
h
6.63 x 10 -34 J - s
-13
=
= 2.3 x 10 m
- 27
5 m
mv (6.941 x 1.66 x 10 kg) x 2.5 x 10
s
10. What scientific achievements were awarded in this year’s (2005) Nobel
Prizes for Chemistry and Physiology or Medicine. (10%)
(i) Chemistry : for the development of the metathesis method in organic
synthesis.
(ii) Physiology or Medicine : for the discovery of the bacterium Helicobacter
pylori and its role in gastritis and peptic ulcer
disease.