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Chemistry 1304.001
Exam 4 (100 points)
Name (please print)
April 15, 2015
On my honor, I have neither given nor received unauthorized aid on this exam.
Signed
Date
Discretely CIRCLE the LETTER ONLY of the answers you select. (5 points each)
1. Arrange the following compounds in order of increasing standard molar entropy at 25 °C.
C3H8 (g), He (g), ZnS (s), and H2O (l).
a.
C3H8 (g) < He (g) < H2O (l) < ZnS (s)
d. C3H8 (g) < He (g) < ZnS (s) < H2O (l)
b.
ZnS (s) < H2O (l) < He (g) < C3H8 (g)
C3H8 (g) < He (g) < ZnS (s) < H2O (l)
e. ZnS (s) < H2O (l) < C3H8 (g) < He (g)
c.
f. none of these
2. Which response includes all the following processes that are accompanied by an increase in entropy?
(1) 2 SO2 (g) + O2 (g) → 2 SO3 (g)
(3)
Br2 (l) → Br2 (g)
(2)
(4)
H2O2 (l) → H2O (l) + ½ O2 (g)
H2O (l) → H2O (s)
a.
b.
1, 2, 3, 4
2, 3, 4
d.
e.
1, 3
1, 2
c.
1, 4
f.
3, 4
3. With respect to the system only, a reaction with ∆H > 0 and ∆S < 0 is predicted to be:
a.
b.
c.
Spontaneous at all temperatures
Spontaneous at high temperatures only
Spontaneous at low temperatures only
d.
e.
f.
Non-spontaneous at all temperatures
Indeterminate without values for ∆H and ∆S
None of these
4. The compound HI has a normal boiling point of –35.4 °C, and its ∆Hvap is 21.16 kJ/mol. The molar entropy of
vaporization (∆Svap) is
a.
b.
89.0 J/K·mol
0.068 J/K·mol
d.
e.
598 J/K·mol
68.6 J/K·mol
c.
75.2 J/K·mol
f.
none of these
5. Consider an electrochemical cell based on the following cell diagram:
Pt | Pu3+ (aq), Pu4+ (aq) || Cl2 (g), Cl– (aq) | Pt
Given that the standard cell voltage is 0.35 V and that the standard reduction potential of chlorine is 1.36 V,
what is the standard reduction potential E°(Pu4+/Pu3+)?
a.
2.37 V
d.
1.01 V
b.
c.
–1.01 V
–1.71 V
e.
f.
1.71 V
none of these
6. A galvanic cell has the overall reaction:
Zn (s) + 2 Eu(NO3)3 (aq) → Zn(NO3)2 (aq) + 2 Eu(NO3)2( aq)
Which is the half reaction occurring at the anode?
a.
Eu3+ (aq) + e- → Eu2+ (aq)
d.
NO2 (g) + H2O (l) → NO3- (aq) + 2 H+ (aq) + e-
b.
Zn (s) + 2 e- → Zn2+ (aq)-
e.
NO3- (aq) + 4 H+ (aq) + 3 e- → NO (g) + 2 H2O (l)
c.
Zn (s) → Zn2+ (aq) + 2 e-
f.
none of these
page 2
7. (5 points) For the process: H2O (l) → H2O (s), ∆H is
(–, +, or 0) and ∆S is
(–, +, or 0).
8. (5 points) From the information below, the free energy of formation of NaBr (s) is
2 NaBr (s) → 2 Na (s) + Br2 (l), where ∆Grexn° = 698 kJ/mol
9.
NH3 (g) + CO (g), Kc = 4.84 at 400 K. If ∆H° for this reaction is
29 kJ/mol, find Kc at 500 K. SHOW ALL WORK.
(12 points)
For the reaction HCONH2 (g)
10. (12 points) A standard hydrogen electrode is immersed in an acetic acid solution. This electrode is connected
by an external circuit to an iron nail dipping into 0.10 M FeCl2. If Ecell is found to be 0.34 V, what is the pH of
the acetic acid solution? SHOW ALL WORK.
page 3
11. (10 points) Calculate the standard free energy, ∆G°, for the electrochemical cell Pb(s) | Pb2+(aq) || Fe3+(aq) |
Fe2+(aq) | Pt(s). SHOW ALL WORK.
Is this a galvanic or electrolytic cell?
12. A constant current flows for 4.00 hours through two electrolytic cells connected in series.
Zn(NO3)2 and the other contains a solution of Al(NO3)3.
deposited in the first cell.
One contains
During this time 2.00 grams of Zn metal are
a. (8 points) How many grams of aluminum are deposited in the second cell? SHOW ALL WORK.
b. (8 points) What is the current flowing, in amps. SHOW ALL WORK.
page 4
13. (10 points) Write balanced oxidation and reduction half reactions and the balanced overall reaction for the
following which ionic redox equation. The reaction occurs in basic solution.
Br2 + SO2 → Br – + SO42–
Balance reduction half reaction
Balanced oxidation half reaction
Overall balanced ionic reaction
Chemistry 1304.001
Exam 4 (100 points)
Name (please print)
April 15, 2015
On my honor, I have neither given nor received unauthorized aid on this exam.
Signed
Date
Discretely CIRCLE the LETTER ONLY of the answers you select. (5 points each)
1. Arrange the following compounds in order of increasing standard molar entropy at 25 °C.
C3H8 (g), He (g), ZnS (s), and H2O (l).
a.
C3H8 (g) < He (g) < H2O (l) < ZnS (s)
d. C3H8 (g) < He (g) < ZnS (s) < H2O (l)
b.
ZnS (s) < H2O (l) < He (g) < C3H8 (g)
C3H8 (g) < He (g) < ZnS (s) < H2O (l)
e. ZnS (s) < H2O (l) < C3H8 (g) < He (g)
c.
f. none of these
2. Which response includes all the following processes that are accompanied by an increase in entropy?
(1) 2 SO2 (g) + O2 (g) → 2 SO3 (g)
(3)
Br2 (l) → Br2 (g)
(2)
(4)
H2O2 (l) → H2O (l) + ½ O2 (g)
H2O (l) → H2O (s)
a.
b.
1, 2, 3, 4
2, 3, 4
d.
e.
1, 3
1, 2
c.
1, 4
f.
3, 4
3. With respect to the system only, a reaction with ∆H > 0 and ∆S < 0 is predicted to be:
a.
b.
c.
Spontaneous at all temperatures
Spontaneous at high temperatures only
Spontaneous at low temperatures only
d.
NonNon-spontaneous at all temperatures
e. Indeterminate without values for ∆H and ∆S
f.
None of these
4. The compound HI has a normal boiling point of –35.4 °C, and its ∆Hvap is 21.16 kJ/mol. The molar entropy of
vaporization (∆Svap) is
a.
b.
89.0 J/K·mol
0.068 J/K·mol
d.
e.
598 J/K·mol
68.6 J/K·mol
c.
75.2 J/K·mol
f.
none of these
5. Consider an electrochemical cell based on the following cell diagram:
Pt | Pu3+ (aq), Pu4+ (aq) || Cl2 (g), Cl– (aq) | Pt
Given that the standard cell voltage is 0.35 V and that the standard reduction potential of chlorine is 1.36 V,
what is the standard reduction potential E°(Pu4+/Pu3+)?
a.
2.37 V
d.
1.01 V
b.
c.
–1.01 V
–1.71 V
e.
f.
1.71 V
none of these
6. A galvanic cell has the overall reaction:
Zn (s) + 2 Eu(NO3)3 (aq) → Zn(NO3)2 (aq) + 2 Eu(NO3)2( aq)
Which is the half reaction occurring at the anode?
a.
Eu3+ (aq) + e- → Eu2+ (aq)
d.
NO2 (g) + H2O (l) → NO3- (aq) + 2 H+ (aq) + e-
b.
Zn (s) + 2 e- → Zn2+ (aq)-
e.
NO3- (aq) + 4 H+ (aq) + 3 e- → NO (g) + 2 H2O (l)
c.
Zn (s) → Zn2+ (aq) + 2 e-
f.
none of these
page 2
7. (5 points) For the process: H2O (l) → H2O (s), ∆H is
(–, +, or 0) and ∆S is
(–, +, or 0).
8. (5 points) From the information below, the free energy of formation of NaBr (s) is
2 NaBr (s) → 2 Na (s) + Br2 (l), where ∆Grexn° = 698 kJ/mol
9.
NH3 (g) + CO (g), Kc = 4.84 at 400 K. If ∆H° for this reaction is
29 kJ/mol, find Kc at 500 K. SHOW ALL WORK.
(12 points)
For the reaction HCONH2 (g)
10. (12 points) A standard hydrogen electrode is immersed in an acetic acid solution. This electrode is connected
by an external circuit to an iron nail dipping into 0.10 M FeCl2. If Ecell is found to be 0.24 V, what is the pH of
the acetic acid solution? SHOW ALL WORK.
page 3
11. (10 points) Calculate the standard free energy, ∆G°, for the electrochemical cell Pb(s) | Pb2+(aq) || Fe3+(aq) |
Fe2+(aq) | Pt(s). SHOW ALL WORK.
Is this a galvanic or electrolytic cell?
12. A constant current flows for 4.00 hours through two electrolytic cells connected in series.
Zn(NO3)2 and the other contains a solution of Al(NO3)3.
deposited in the first cell.
One contains
During this time 2.00 grams of Zn metal are
a. (8 points) How many grams of aluminum are deposited in the second cell? SHOW ALL WORK.
b. (8 points) What is the current flowing, in amps. SHOW ALL WORK.
page 4
13. (10 points) Write balanced oxidation and reduction half reactions and the balanced overall reaction for the
following which ionic redox equation. The reaction occurs in basic solution.
Br2 + SO2 → Br – + SO42–
Balance reduction half reaction
Balanced oxidation half reaction
Overall balanced ionic reaction