Name: ________________________ Class: ___________________ Date: __________
ID: A
CHM-124 Electrochemistry Review
____
1. Given the following reaction in acidic media:
Fe2+ + Cr2O72–  Fe3+ + Cr3+
answer the following question: The coefficient for water in the balanced reaction is:
A) 1
B) 3
C) 5
D) 7
E) none of these
____
2. For the reaction of sodium bromide with chlorine gas to form sodium chloride and bromine, the
appropriate half-reactions are (ox = oxidation and re = reduction):
A) ox: Cl2 + 2e–  2Cl–;
re: 2Br–  Br2 + 2e–
B) ox: 2Br–  Br2 + 2e–;
re: Cl2 + 2e–  2Cl–
C) ox: Cl + e–  Cl–;
re: Br  Br– + e–
–
2–
D) ox: Br + 2e  Br ;
re: 2Cl–  Cl2 + 2e–
E) ox: 2Na+ + 2e–  2Na; re: 2Cl–  Cl2 + 2e–
____
3. How many electrons are transferred in the following reaction when it is balanced in acidic
solution? SO32–(aq) + MnO4–(aq)  SO42–(aq) + Mn2+(aq)
A) 6
B) 2
C) 10
D) 5
E) 3
____
4. Ammonium metavandate reacts with sulfur dioxide in acidic solution as follows (hydrogen ions
and H2O omitted):
xVO3– + ySO2  xVO2+ + ySO42–
The ratio x : y is
A) 1 : 1
B) 1 : 2
C) 2 : 1
D) 1 : 3
E) 3 : 1
1
Name: ________________________
ID: A
____
5. When the equation Cl2  Cl– + ClO3– (basic solution) is balanced using the smallest
whole-number coefficients, the coefficient of OH – is:
A) 1
B) 12
C) 3
D) 4
E) 6
____
6. For the redox reaction 2Fe2+ + Cl2  2Fe3+ + 2Cl– which of the following are the correct
half-reactions?
I.
II.
III.
IV.
V.
A)
B)
C)
D)
E)
Cl2 + 2e–  2Cl–
Cl  Cl– + e–
Cl2  2Cl– + 2e–
Fe2+  Fe3+ + e–
Fe2+ + e–  Fe3+
I and IV
I and V
II and IV
II and V
III and IV
____
7. What is the oxidation state of Hg in Hg2Cl2?
A) +2
B) –1
C) –2
D) +1
E) 0
____
8. How many electrons are transferred in the following reaction?
Sn  2HCl  SnCl2  H2
A)
B)
C)
D)
E)
0
1
2
4
not enough information given
2
Name: ________________________
____
ID: A
9. The following questions refer to a galvanic cell that utilizes the following reaction (unbalanced):
(AuCl4)–(aq) + Cu(s)  Au(s) + Cl–(aq) + Cu2+(aq)
Determine the number of electrons transferred during the reaction (when balanced).
A) 2
B) 3
C) 4
D) 6
E) 9
____
10. Which energy conversion shown below takes place in a galvanic cell?
A) electrical to chemical
B) chemical to electrical
C) mechanical to chemical
D) chemical to mechanical
E) mechanical to electrical
____
11. Which of the following reactions is possible at the anode of a galvanic cell?
A) Zn  Zn2+ + 2e–
B) Zn2+ + 2e–  Zn
C) Zn2+ + Cu  Zn + Cu2+
D) Zn + Cu2+  Zn2+ + Cu
E) two of these
____
12. Which of the following is true for the cell shown here? Zn(s) | Zn2+(aq)  Cr3+(aq) | Cr(s)
A) The electrons flow from the cathode to the anode.
B) The electrons flow from the zinc to the chromium.
C) The electrons flow from the chromium to the zinc.
D) The chromium is oxidized.
E) The zinc is reduced.
____
13. The anode in a voltaic (galvanic) cell and in an electrolytic cell is
A) positive in both cells
B) the site of oxidation and of reduction, respectively
C) the site of reduction and of oxidation, respectively
D) the site of oxidation in both cells
E) the site of reduction in both cells
____
14. Which statement is always true of the cathode in an electrochemical cell?
A) It is considered the “negative” electrode.
B) It is considered the “positive” electrode.
C) Reduction occurs here.
D) Metal is plated out here.
E) Negative ions flow toward the cathode.
3
Name: ________________________
____
ID: A
15. A strip of copper is placed in a 1 M solution of copper nitrate and a strip of silver is placed in a 1 M
solution of silver nitrate. The two metal strips are connected to a voltmeter by wires and a salt
bridge connects the solutions. The following standard reduction potentials apply:
Ag+(aq) + e–  Ag(s)
Cu2+(aq) + 2e–  Cu(s)
 +0.80 V
 +0.34 V
Which of the following statements is false?
A) Electrons flow in the external circuit from the copper electrode to the silver
electrode.
B) The silver electrode increases in mass as the cell operates.
C) There is a net general movement of silver ions through the salt bridge to the
copper half-cell.
D) Negative ions pass through the salt bridge from the silver half-cell to the copper
half-cell.
E) Some positive copper ions pass through the salt bridge from the copper half-cell
to the silver half-cell.
____
16. Which of the following is the strongest oxidizing agent?
MnO4– + 4H+ + 3e–  MnO2 + 2H2O
I2 + 2e–  2I–
Zn2+ + 2e–  Zn
A)
B)
C)
D)
E)
____
 1.68 V
 0.54 V
 –0.76 V
MnO4–
I2
Zn2+
Zn
MnO2
17. Which metal, Al or Ni could reduce Zn2+ to Zn(s) if placed in a Zn2+(aq) solution?
Zn2+ + 2e–  Zn
Al3+ + 3e–  Al
Ni2+ + 2e–  Ni
A)
B)
C)
D)
E)
 –0.76 V
 –1.66 V
 –0.23 V
Al
Ni
Both Al and Ni would work.
Neither Al nor Ni would work.
Cannot be determined.
4
Name: ________________________
____
ID: A
18. Consider the galvanic cell shown below (the contents of each half-cell are written beneath each
compartment):
0.50 M Br2
0.10 M Br–
0.20 M Cr3+
The standard reduction potentials are as follows:
Cr3+(aq) + 3e–  Cr(s)
Br2(aq) + 2e–  2Br–(aq)
 –0.727 V
 +1.090 V
What is  for this cell?
A) 1.817 V
B) 0.363 V
C) –0.363 V
D) 4.724 V
E) 1.316 V
5
Name: ________________________
____
ID: A
19. Refer to the galvanic cell below (the contents of each half-cell are written beneath each
compartment):
0.10 M MnO4–
0.20 M Mn2+
0.010 M H+
0.40 M Cr3+
0.30 M Cr2O72–
0.010 M H+
The standard reduction potentials are as follows:
MnO4– + 8H+ + 5e–  Mn2+ + 4H2O,  1.506 V
Cr2O72– + 14H+ + 6e–  2Cr3+ + 7H2O,  1.330 V
What is the value of cell?
A) –0.176
B) 2.836
C) 0.176
D) 0.676
E) 6.200
____
20. The galvanic cell described by Zn(s) | Zn2+(aq) || Cu2+(aq) | Cu(s) has a standard cell potential of
1.101 volts. Given that Zn(s)  Zn2+(aq) + 2e– has an oxidation potential of 0.764 volts, determine
2+
the reduction potential for Cu .
A) 1.865 V
B) –1.865 V
C) –0.337 V
D) 0.337 V
E) none of these
6
Name: ________________________
____
ID: A
21. The following question refers to the following system:
3Ag(s) + NO3–(aq) + 4H+(aq)  3Ag+(aq) + NO(g) + 2H2O(l)
Anode reaction:
Ag  Ag+(aq) + e–
Cathode reaction: NO3–(aq) + 4H+(aq) + 3e–  NO(g) + 2H2O(l)
 –0.7990 V
 0.9644 V
Determine the standard cell potential.
A) –1.7634 V
B) 0.1654 V
C) 2.0942 V
D) 3.5268 V
E) 0.5878 V
____
22. Of Sn2+, Ag+, and/or Zn2+, which could be reduced by Cu?
A) Sn2+
B) Ag+
C) Zn2+
D) Two of them could be reduced by Cu.
E) All of them could be reduced by Cu.
____
23. What is the cell reaction for the voltaic cell Cr(s) | Cr3+(aq) || Cl–(aq) | Cl2(g) | Pt?
A) Cr(s) + 2Cl–(aq)
Cl2(g) + Cr3+(aq)
B) 2Cr3+(aq) + 6Cl–(aq)
2Cr(s) + 3Cl2(g)
3+
C) Cr(s) + 3Cl2(g)
Cr (s) + 2Cl–(aq)
D) 2Cr(s) + 3Cl2(g)
2Cr3+(aq) + 6Cl–(aq)
E) none of these
____
24. What is the balanced chemical equation corresponding to the following cell diagram?
Na(s) | Na+(aq) || Cu2+(aq) | Cu(s)
A)
B)
C)
D)
E)
2Na(s) + 2Na+(aq)  Cu2+(aq) + Cu(s)
Cu(s) + 2Na+(aq)  2Na(s) + Cu2+(aq)
2Na(s) + Cu(s)  2Na+(aq) + Cu2+(aq)
Cu2+(aq) + Cu(s)  2Na(s) + 2Na+(aq)
2Na(s) + Cu2+(aq)  2Na+(aq) + Cu(s)
7
Name: ________________________
____
ID: A
25. The following has a potential of 0.92 V:
2

2
2Hg (aq)  H2 (g)  2H (aq)  Hg2 (aq)
If the concentrations of the ions were 1.0 M and the pressure of H2 were 1.0 atm, then  for the
2
2
half-reaction 2Hg (aq)  2e   Hg2 (aq) would be
A)
B)
C)
D)
E)
____
–0.92 V
–0.46 V
0.46 V
0.92 V
none of these
26. Consider the following electrode potentials:
Mg2+ + 2e–  Mg
V2+ + 2e–  V
Cu2+ + e–  Cu+
= –2.37 V
= –1.19 V
= 0.16 V
Which one of the reactions below will proceed spontaneously from left to right?
A) Mg2+ + V V2+ + Mg
B) Mg2+ + 2Cu+  2Cu2+ + Mg
C) V2+ + 2Cu+  V + 2Cu2+
D) V + 2Cu2+  V2+ + 2Cu+
E) none of these
____
27. What is cell for the following electrochemical equation? (red(Li+/Li) = –3.04 V, red(Cu2+/Cu) =
0.342 V)
2Li(s) + Cu2+(aq)  2Li+(aq) + Cu(s)
A)
B)
C)
D)
E)
–5.738 V
6.422 V
3.382 V
–3.382 V
–6.422 V
8
Name: ________________________
____
ID: A
28. Given:
2H+(aq) + 2e–  H2(g); 0.00 V
K+(aq) + e–  K(s); –2.93 V
F2(g) + 2e–  2F–(aq); 2.87 V
Al3+(aq) + 3e–  Al(s); –1.66 V
Pb2+(aq) + 2e–  Pb(s); –0.13 V
Under standard-state conditions, which is the strongest reducing agent?
A) H+
B) K
C) F–
D) Al3+
E) Pb2+
____
29. Which of the following statements is true concerning the electrochemical cell depicted below?
Mg | Mg2+(aq) || Cu2+(aq) | Cu
Mg2+(aq) + 2e–  Mg(s);    –2.38 V
Cu2+(aq) + 2e–  Cu(s);    0.34 V
A)
B)
C)
D)
E)
____
The cell reaction is spontaneous with a standard cell potential of 2.72 V.
The cell reaction is spontaneous with a standard cell potential of 2.04 V.
The cell reaction is nonspontaneous with a standard cell potential of –2.72 V.
The cell reaction is nonspontaneous with a standard cell potential of –2.04 V.
The cell is at equilibrium.
30. Which of the following statements is true concerning the electrochemical cell depicted below?
Ca | Ca2+(aq) || K+(aq) | K
Ca2+(aq) + 2e–  Ca(s);  = –2.87 V
K+(aq) + e–  K(s);  = –2.93 V
A)
B)
C)
D)
E)
____
The cell reaction is spontaneous with a standard cell potential of 0.06 V.
The cell reaction is nonspontaneous with a standard cell potential of –5.80 V.
The cell reaction is nonspontaneous with a standard cell potential of –0.06 V.
The cell reaction is spontaneous with a standard cell potential of 5.80 V.
The cell is at equilibrium.
31. Which of the following cell diagrams represents a galvanic cell? ( red(Sn2+/Sn) = –0.138V,
red(H+/H2) = 0.00 V)
A) Pt(s), H2(g) | H+(aq) || Sn2+(aq) | Sn(s)
B) Sn(s) | Sn2+(aq) || H+(aq) | H2(g), Pt(s)
C) Sn(s), H2(g) | H+(aq) || Sn2+(aq) | Pt(s)
D) Pt(s) | Sn2+(aq) || H+(aq) | H2(g), Sn(s)
E) Sn(s) | Pt(s) || H+(aq), Sn2+(aq) | H2(g)
9
Name: ________________________
____
ID: A
32. The reduction potentials for Au3+ and Ni2+ are as follows:
Au3+ + 3e–  Au,  = +1.50 V
Ni2+ + 2e–  Ni,  = –0.229 V
Calculate G° (at 25°C) for the reaction:
2Au3+ + 2Ni  3Ni2+ + 2Au
A)
B)
C)
D)
E)
1.00  10 kJ
2
7.36  10 kJ
2
7.36  10 kJ
2
1.67  10 kJ
3
1.00  10 kJ
3
____
33. For a certain reaction, H° = –74.4 kJ and S° = –227 J/K. If n = 3, calculate  for the reaction at
25°C.
A) 0.0233 V
B) 0.491 V
C) 0.277 V
D) 0.0700 V
E) 0.237 V
____
34. The standard free energies of formation of several species are:
H+(aq)
H2O(l)
CH3OH(aq)
HCOOH(aq)
e–
kJ/mol
0
–237.0
–163.0
–351.2
0
What is the standard reduction potential of methanoic acid in aqueous solution (i.e., for HCOOH +
4H+ + 4e–  CH3OH + H2O)?
A)
B)
C)
D)
E)
0.126 V
0.506 V
–0.718 V
–0.126 V
1.946 V
10
Name: ________________________
____
ID: A
35. Determine G° for a cell that utilizes the following reaction:
Cl2(g) + 2Br–(aq)  2Cl–(aq) + Br2(l)
The standard reduction for the chlorine gas is 1.360 volts and the standard reduction for the
bromine liquid is about 1.078 volts.
A) –470 kJ
B) –27.2 kJ
C) –235 kJ
D) –54.4 kJ
E) –23.9 kJ
____
36. What is G° for the following electrochemical equation? (°red(Ag+/Ag) = 0.800 V, °red(Cd2+/Cd)
= –0.403 V)
2Ag(s) + Cd2+(aq)  2Ag+(aq) + Cd(s)
A)
B)
C)
D)
E)
____
–232 kJ/mol
116 kJ/mol
232 kJ/mol
464 kJ/mol
–464 kJ/mol
37. The following question refers to the following system:
3Ag(s) + NO3–(aq) + 4H+(aq)  3Ag+(aq) + NO(g) + 2H2O(l)
Anode reaction:
Ag  Ag+(aq) + 1e–
Cathode reaction: NO3–(aq) + 4H+(aq) + 3e–  NO(g) + 2H2O(l)
Determine the equilibrium constant at 25°C.
2
A) 6.097  10
89
B) 2.965  10
9
C) 4.412  10
8
D) 2.266  10
E) 3.117
11
° = –0.7990 V
° = 0.9636 V
Name: ________________________
____
ID: A
38. Consider an electrochemical cell with a zinc electrode immersed in a solution of Zn 2+ and a silver
electrode immersed in a solution of Ag+.
Zn2+ + 2e–  Zn
° = –0.76 V
+
–
Ag + e  Ag
° = 0.80 V
 2  
  
If  Zn  is 0.050 M and  Ag  is 11.26 M, calculate .




0
A)
B)
C)
D)
E)
____
0
1.46 V
1.76 V
1.36 V
1.66 V
1.63 V
39. The reduction potentials for Ni2+ and Sn2+ are as follows:
Ni2+ + 2e–  Ni, ° = –0.231 V
Sn2+ + 2e–  Sn, ° = –0.140 V
Calculate the equilibrium constant at 25 °C for the reaction:
Sn2+ + Ni
A)
B)
C)
D)
E)
____
Sn + Ni2+
3.6  10
35
5.9
4
8.3  10
3
1.2  10
12
40. What is  of the following cell reaction at 25°C? °cell = 0.460 V.
Cu(s) | Cu2+(0.014 M) || Ag+(0.20 M) | Ag(s)
A)
B)
C)
D)
E)
____
0.282 V
0.491 V
0.460 V
0.473 V
0.494 V
41. For the cell Cu(s) | Cu2+ || Ag+ | Ag(s), the standard cell potential is 0.46 V. A cell using these
reagents was made, and the observed potential was 0.16 V at 25oC. What is a possible explanation
for the observed voltage?
A) The Ag+ concentration was larger than the Cu2+ concentration.
B) The Cu2+ concentration was larger than the Ag+ concentration.
C) The Ag electrode was twice as large as the Cu electrode.
D) The volume of the Cu2+ solution was larger than the volume of the Ag+ solution.
E) The volume of the Ag+ solution was larger than the volume of the Cu2+ solution.
12
Name: ________________________
____
ID: A
42. What is the value of the reaction quotient, Q, for the voltaic cell constructed from the following
two half-reactions when the Zn2+ concentration is 0.0103 M and the Ag+ concentration is 1.35 M?
Zn2+(aq) + 2e–  Zn(s); ° = –0.76 V
Ag+(aq) + e–  Ag(s); ° = 0.80 V
A)
B)
C)
D)
E)
____
177
131
2
1.25  10
3
7.63  10
3
5.65  10
43. Which of the following statements is true concerning the electrochemical cell described below at
25oC?
Cu | Cu2+(0.816 M) || Cu2+(0.843] M) | Cu
Cu2+(aq) + 2e–  Cu(s); ° = 0.34 V
A)
B)
C)
D)
E)
____
The cell reaction is spontaneous with a cell potential of 4.81 mV.
The cell reaction is spontaneous with a cell potential of 0.418 mV.
The cell reaction is nonspontaneous with a cell potential of –0.418 mV.
The cell reaction is nonspontaneous with a cell potential of –4.81 mV.
The cell reaction is spontaneous with a cell potential of 0.340 V.
44. What is the potential at 25°C for the following cell?
Cr | Cr3+(0.015 M) || Ag+(0.00025 M) | Ag
Cr3+ + 3e–
Ag+ + e–
A)
B)
C)
D)
E)
____
Cr
Ag
° = –0.73 V
° = 0.80 V
2.09 V
1.35 V
0.95 V
1.71 V
1.49 V
45. How many moles of electrons are produced from a current of 14.4 A in 3.20 hours?
A) 4.78  10–4 mol
B) 1.72 mol
C) 46.1 mol
D) 3.35 mol
E) 9.33  103 mol
13
Name: ________________________
ID: A
An antique automobile bumper is to be chrome plated. The bumper, which is dipped into an acidic
2
Cr 2 O 7 solution, serves as a cathode of an electrolytic cell. The atomic mass of Cr is 51.996; 1
faraday = 96,485 coulombs.
____
46. If oxidation of H2O occurs at the anode, how many moles of oxygen gas will evolve for every 151
grams of Cr(s) deposited?
A) 4.36
B) 0.726
C) 17.4
D) 11.6
E) 3.87
____
47. If the current is 10.0 amperes, how long will it take to deposit 105 grams of Cr(s) onto the bumper?
A) 5.41 h
B) 1.35 days
C) 54.1 min
D) 2.02 min
E) 2 mo, 25 days, 14 h, and 6 s
____
48. Copper is electroplated from CuSO4 solution. A constant current of 3.19 amp is applied by an
external power supply. How long will it take to deposit 1.00  102 g of Cu? The atomic mass of
copper is 63.546.
A) 26.4 h
B) 13.2 min
C) 2.03 days
D) 9.57 s
E) 3.78 h
____
49. What quantity of charge is required to reduce 27.8 g of CrCl3 to chromium metal?
(1 faraday = 96,485 coulombs)
4
A) 1.69  10 C
4
B) 5.08  10 C
2
C) 8.05  10 C
2
D) 2.68  10 C
E) none of these
____
50. If a constant current of 5.0 amperes is passed through a cell containing Cr 3+ for 1.0 hour, how
many grams of Cr will plate out onto the cathode? (The atomic mass of Cr is 51.996.)
A) 9.7 g
4
B) 9.0  10 g
C) 3.2 g
D) 29 g
2
E) 6.2  10 g
14
Name: ________________________
ID: A
____
51. If an electrolysis plant operates its electrolytic cells at a total current of 1.8  106 amp, how long
will it take to produce one metric ton (one million grams) of Mg(s) from seawater containing
Mg2+? (1 faraday = 96,485 coulombs)
A) 1.2 h
B) 1.2 days
C) 37 min
D) 0.61 h
E) 0.31 year
____
52. Nickel is electroplated from a NiSO 4 solution. A constant current of 5.50 amp is applied by an
external power supply. How long will it take to deposit 100. g of Ni? The atomic mass of Ni is
58.69.
A) 16.6 h
B) 8.30 h
C) 18.2 min
D) 55.4 s
E) 1.09 s
____
53. How many seconds would it take to deposit 18.2 g of Ag (atomic mass = 107.87) from a solution
of AgNO3 using a current of 10.00 amp?
3
A) 3.26  10 s
2
B) 8.14  10 s
3
C) 4.88  10 s
3
D) 1.63  10 s
2
E) 5.43  10 s
____
54. What mass of chromium could be deposited by electrolysis of an aqueous solution of Cr 2(SO4)3 for
145 minutes using a constant current of 11.0 amperes?
A) 0.187 g
B) 154.7 g
C) 0.287 g
D) 25.8 g
E) 17.2 g
15
ID: A
CHM-124 Electrochemistry Review
Answer Section
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38.
D
B
C
C
E
A
D
C
D
B
A
B
D
C
C
A
A
A
C
D
B
B
D
E
D
D
C
B
A
C
B
E
A
A
D
C
D
D
1
ID: A
39.
40.
41.
42.
43.
44.
45.
46.
47.
48.
49.
50.
51.
52.
53.
54.
E
D
B
E
B
B
B
A
B
A
B
C
A
A
D
E
2