General Chemistry Ii Jasperse - Electrochemistry Extra Practice Problems With Answers Page 10
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Free Energy and Equilibrium. Key Equation: ∆G˚ = –96.5nE˚ cell (∆G˚ in kJ/mol)
51. Given the electrochemical reaction shown, what is the standard free energy change ΔG° if E˚ = +1.61 V?
2+
2+
Mg / Mg
(aq) // Zn
(aq) / Zn
E˚ = +1.61 V
T
a. -311 kJ/mol
b. +311 kJ/mol
c. -155 kJ/mol
d. +155 kJ/mol
e. none of the above
1. Find "n"
2. Plug and Chug
3. Check: a positive Eº means you
must have a negative delta G
52. The oxidation of hydrogen by oxygen is one of the most-used reactions in fuel-cell technology. The overall reaction,
which is given below, has a ΔG° value of –474 kJ/mol. What is the standard cell potential for this fuel cell?
2H
(g) + O
(g) → 2H
O(l)
ΔG° = –474 kJ/mol
2
2
2
a.
2.46 V
d.
2.46 V
b.
4.91 V
e.
1.50 V
c.
1.23 V
53. What is ΔG° for the following balanced reaction, if E˚ = +2.431 V?
T
3+
3+
Al(s) + Fe
(aq) → Al
(aq) + Fe(s)
E˚ = +2.431 V
a. -704 kJ/mol
b. +704 kJ/mol
c. -235 kJ/mol
d. -469 kJ/mol
e. none of the above
54. The oxidation of methanol, as described by the equation below, has a ΔG° value of –937.9 kJ/mol. What is the standard
cell potential for a methanol fuel cell?
2CH
OH + 3O
→ 2 CO
+ 4H
O
ΔG° = –937.9 kJ/mol
3
2
2
2
a.
0.405 V
d.
–2.43 V
b.
9.72 V
e.
–9.72 V
c.
0.810 V
T
55. For the following reaction, all of the reactants and products are in their standard states/standard 1.0M concentrations.
Which of the following statements must be true?
Zn (s) + SnBr
(aq) ! ZnBr
(aq) + Sn (s)
E˚ = +0.60 V
2
2
a. The reaction would be product-favored as written
b. ∆G˚ for the reaction as written is positive
c. Zinc is undergoing reduction
d. none of the above
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