REVIEW QUESTIONS
We will look at a number of these multiple choice questions and
problems during the last two lectures.
Multiple Choice Questions
1. At 298K, Keq = 4.34×10–5 for the reaction: PH3(g) + HI(g) PH4I(s). ΔG° for this reaction is
A) 17.6 kJ
B) 24.9 kJ
C) 0 kJ
D) –16.7 kJ
E) –30.2 kJ
2. At 298K, the reaction: H2(g) + ½ O2(g) → H2O(l) is
A) disfavoured by the enthalpy change as written.
B) favoured by the entropy change as written.
C) favoured by both the enthalpy and entropy changes as written.
D) spontaneous in the reverse direction.
E) spontaneous as written.
3. The boiling point of CH3COOH(l) can be calculated to be:
A) 426°C
B) 153°C
C) 0.426°C
D) 799°C
E) –153°C
4. The oxidation state of P in Na2HPO4 is
A) +1
B) –1
C) +5
D) +3
E) –3
5. Given Zn(s) + Sn2+(aq) → Sn(s) + Zn2+(aq)
The standard free energy change in kJ/mol for this reaction at 298K is:
A) 1.2×102
B) –21.2
C) –60
D) –1.2×102
E) 60
6. The value of the equilibrium constant, K, for the reaction
Br2(l) + H2O(l) → H+(aq) + Br–(aq) + HOBr(aq) at 298K is:
A) 1.6×10–9
B) 2.5×104
C) 4.1×10–5
D) 6.1×108
E) 1.2×10–4
7. A current is passed through a molten mixture of ZnI2 and KCl. The product at the cathode is:
A) K+
B) Cl–
C) I2
D) Zn
E) K
8. Use the following experimental data for NO(g) + Cl2(g) → NOCl2(g)
[NO]
1.01×10–2
1.02×10–2
2.02×10–2
3.02×10–2
[Cl2]
5.30×10–2
1.05×10–1
1.51×10–1
1.53×10–1
The order of Cl2(g) in the rate law is:
A) 1
B) none of these
Initial Rate
5.00×10–2
1.99×10–1
9.02×10–1
1.34
C) 2
D) 3
E) 0
1
9. Tritium is radioactive and decays by a first order process with a half life of 12.5 years. If an
experiment starts with 1.00×10–6 moles of tritium then the number of moles of tritium left after
4.5 years is
A) 1.1×10–7
B) 7.8×10–7
C) 3.6×10–7
D) 4.8×10–6
E) 1.0×10–9
10. The rate constant for a particular first order reaction at 500°C is 1.20×10–4 s–1. The rate constant
for this reaction at 600°C is 6.80×10–3 s–1. The activation energy in kJ/mol for this reaction is:
A) 27.4
B) 226
C) 318
D) 3.36
E) 33.6
Problems
11. Calculate the work needed to make room for products in the combustion of 2 moles of C4H10(g)
to carbon dioxide and water vapor at STP (1 L · atm = 101.325 J).
12. At the normal boiling point of CH3CH2OH(l), 315.7 K, the value of the standard enthalpy of
vapourization is 38.7 kJ•mol-1. Assuming that CH3CH2OH(g) behaves as an ideal gas and that the
molar volume of CH3CH2OH(l) is negligible compared to that of CH3CH2OH(g), calculate the
values of q, w, ΔUo, ΔSo, and ΔGo for the reversible vapourisation of 1 mole of CH3CH2OH(l) at
315.7 K and 1 atm.
13. If the Ksp of AgI is 8.5×10–17 at 298 K, calculate ΔGr for the rxn of 5 mL of 0.20 M AgNO3(aq)
with 5 mL of 0.20 M NaI(aq) at 298 K.
14. Balance the reaction: IO3–(aq) + I–(aq) → I3–(aq) which occurs in acidic solution.
15. Balance the following equation in basic solution:
OCl–(aq) + SCN–(aq) → SO42–(aq) + CO32–(aq) + NO3–(aq) + Cl–(aq)
16. The overall reaction in the lead storage battery is
Pb(s) + PbO2(s) + 2H+(aq) + 2HSO4–(aq) → 2PbSO4(s) + 2H2O(l); E° = 2.04V at 298K
a) Calculate E at 298K for this battery when [H+] = [HSO4–] = 4.5M
b) For the cell reaction in the lead storage battery, ΔH° = – 315.9 kJ and ΔS° = 263.5 J/K.
Calculate E° at –20°C.
c) Calculate E at –20°C when [H+] = [HSO4–] = 4.5M
17. Consider a voltaic cell based on the following half reaction
VO2+(aq) + 2H+(aq) + e– → VO2+(aq) + H2O(l) ; E° = 1.00V
Zn2+(aq) + 2e– → Zn(s); E° = –0.76V
a) Write the overall cell reaction which is spontaneous under standard conditions and determine
E° for this cell at T = 298K.
b) Determine the cell potential, E, at T = 298K if [VO2+] = 2.0M, [H+] = 0.50M,
[VO2+] = 1.10×10–2 M and [Zn2+] = 1.0×10–1 M
18. The standard voltage of the cell: Pt(s)⏐Hg(l)⏐Hg2Cl2(s)⏐Cl–(aq) || Hg22+(aq)⏐Ηg(l) ⏐ Pt(s)
is +0.529 V at 25oC. Calculate the Ksp of Hg2Cl2.
2
19. Consider a voltaic cell at 298K with the net cell equation:
H2(g) + 2AgCl(s) → 2H+(aq) + 2Cl–(aq) + 2Ag(s)
a) Write the appropriate half reactions and calculate the cell potential under standard conditions.
b) With [Cl–] = 1.0M & P(H2) = 1.00 atm, the measured cell voltage is +0.340V. Calculate pH.
20. When 1 M NiBr2(aq) is electrolyzed at pH = 7, what is the product formed at the anode (or
cathode)? Assume that no overpotential is present and standard conditions are used. If one were
to assume an overpotential of 0.50 V in the production of any gases, does your answer change?
21. Sodium metal is produced commercially by the electrolysis of molten sodium chloride. Calculate
the mass of sodium and the volume of chlorine gas measured at 1 atm and 25°C produced by a
current of 20.0 amperes in 1.00 hour.
22. How many moles of O2(g) are produced by electrolysis of Na2SO4(aq) if 0.240 A is passed
through the solution for 65.0 minutes?
23. A proposed mechanism for the gas phase reaction of chlorine with chloroform is:
Br(g) 2Br(g)
K1, fast equilibrium
Br(g) + CHBr3(g) → HBr(g) + CBr3(g)
k2, slow
CBr3(g) + Br(g) → CBr4(g)
k3, fast
Write the overall reaction and find an expression for the rate law.
24. Plot the energy profiles (and identify Ea, forward) for the following reaction mechanisms:
(i) a slow step followed by a fast step (overall endothermic reaction )
(ii) a fast step followed by a slow step (exothermic reaction)
DATA
1 atm = 1.013×105 Pa
1 L = 10–3 m3
R = 8.314 J mol–1 K–1
F = 96 485 C/mol
At T = 298K, 2.303RT/F = 0.0591 V and RT/F = 0.025693
Thermodynamics Data at T = 298K
H2O(g)
H2O(l)
CH3COOH(l)
CH3COOH(g)
ΔH°f, kJ/mol ΔG°f, kJ/mol S°, J/mol K
– 241.8
– 228.6
188.7
– 285.8
– 237.2
69.9
– 484.5
– 390.0
159.8
– 432.25
– 65.28
282.4
Standard Reduction Potentials at T = 298K
–
E°, V
–
+1.36
Cl2(l) + 2e → 2Cl (aq)
+
–
–
HOBr(aq) + H (aq) + 2e → Br (aq) + H2O(l) +1.32
+1.23
O2(g) + 4H+(aq) + 4e–→ H2O(l)
–
–
+1.07
Br2(l) + 2e → 2Br (aq)
+0.799
Ag+(aq) + e– → Ag(s)
+0.535
I2(s) + 2e– → 2I–(aq)
–
–
+0.222
AgCl(s) + e → Ag(s) + Cl (aq)
0.000
H+(aq) + e– → H2(g)
2+
–
–
0.14
Sn (aq) + 2e → Sn(s)
3
Ni2+(aq) + 2e– → Ni(s)
Zn2+(aq) + 2e– → Zn(s)
H2O(l) + 2e– → H2(g) + 2OH–(aq)
K+(aq) + e– → K(s)
– 0.24
– 0.76
– 0.83
– 2.92
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