Ch. 11 Practice Problems
1.
Ammonium metavanadate reacts with sulfur dioxide in acidic solution as follows (hydrogen ions and H 2O omitted):
–
–
xVO3 + ySO2  xVO2+ + ySO42
The ratio x : y is
A)
B)
C)
D)
E)
1:1
1:2
2:1
1:3
3:1
2.
What is the oxidation state of Mn in MnO2?
A) +2
B) +4
C) +9
D) -1
E)
+3
3.
How many electrons are transferred in the following reaction?
2Cr2O72- + 14H+ + 6Cl–  2Cr3+ + 3Cl2 + 7H2O
A)
B)
C)
D)
E)
4.
2
4
6
8
none of these
How many electrons are transferred in the following reaction?
SO32–(aq) + MnO4–(aq)  SO42–(aq) + Mn2+(aq)
A)
B)
C)
D)
E)
6
2
10
4
3
Use the following to answer question 5:
Refer to the galvanic cell below (the contents of each half-cell are written beneath each compartment).
The standard reduction potentials are as follows:
MnO4– + 8H+ + 5e–  Mn2+ + 4H 2O
Cr2O72– +14H+ + 6e–  2 Cr3+ +7H2O
5.
What is the oxidation state of Cr in Cr2O72–?
A) +7
B) +6
C) +12
D) –1
E)
–2
6.
The following reaction occurs in basic solution:
Ag+ + Cu  Ag + Cu2+
E = 1.51 V
E = 1.33 V
When the equation is balanced, what is the sum of the coefficients?
A)
B)
C)
D)
E)
7.
When the equation for the following reaction in basic solution is balanced, what is the sum of the coefficients?
MnO2 + HO2–  MnO4–
A)
B)
C)
D)
E)
8.
Electrons flow in the external circuit from the copper electrode to the silver electrode.
The silver electrode increases in mass as the cell operates.
There is a net general movement of silver ions through the salt bridge to the copper half-cell.
Negative ions pass through the salt bridge from the silver half-cell to the copper half-cell.
Some positive copper ions pass through the salt bridge from the copper half-cell to the silver half-cell.
Which metal, Al or Ni, could reduce Zn2+ to Zn(s) if placed in a Zn2+(aq) solution?
E° = -0.76 V
Zn2+ + 2e-  Zn
E° = -1.66 V
Al3+ + 3e-  Al
E° = -0.23 V
Ni2+ + 2e-  Ni
A)
B)
C)
D)
E)
12.
12
15
19
23
27
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) E° = +0.80 V
Cu2+(aq) + 2e–  Cu(s) E° = +0.34 V
When the voltmeter is removed and the two electrodes are connected by a wire, which of the following does not take place?
A)
B)
C)
D)
E)
11.
13
8
10
20
11
The reaction below occurs in basic solution. In the balanced equation, what is the sum of the coefficients?
Zn + NO3–  Zn(OH)42– + NH3
A)
B)
C)
D)
E)
10.
11
31
14
9
18
When the equation for the following reaction in basic solution is balanced, what is the sum of the coefficients?
MnO4–(aq) + CN–(aq)  MnO2(s) + CNO–(aq)
A)
B)
C)
D)
E)
9.
8
7
6
5
4
Al
Ni
Both Al and Ni would work.
Neither Al nor Ni would work.
This cannot be determined.
Which of the following is the best reducing agent?
Cl2 + 2e-  2ClMg2+ + 2e-  Mg
2H+ + 2e-  H2
E° = 1.36 V
E° = -2.37 V
E° = 0.00 V
A)
B)
C)
D)
E)
13.
The following two half-reactions take place in a galvanic cell. At standard conditions, what species are produced at each
electrode?
E° = –0.14 V
Sn2+ + 2e–  Sn
2+
–
E° = 0.34 V
Cu + 2e  Cu
A)
B)
C)
D)
E)
14.
Cl2
H2
Mg
Mg2+
Cl-
Sn is produced at the anode, and Cu2+ is produced at the cathode.
Sn is produced at the anode, and Cu is produced at the cathode.
Sn is produced at the cathode, and Cu2+ is produced at the anode.
Cu is produced at the cathode, and Sn2+ is produced at the anode.
Cu is produced at the anode, and Sn2+ is produced at the cathode.
Which of the following is the strongest oxidizing agent?
E° = 1.68 V
MnO4– + 4H+ + 3e–  MnO2 + 2H 2O
E° = 0.54 V
I2 + 2e–  2I–
E° = -0.76 V
Zn2+ + 2e–  Zn
A) MnO4–
B) I2
C) Zn2+
D) Zn
E)
MnO2
Use the following to answer questions 15-17:
Reaction
Na+ + e–  Na
Al3+ + 3e–  Al
Fe2+ + 2e–  Fe
Co 2+ + 2e–  Co
Cu2+ + 2e–  Cu
Ag+ + e–  Ag
Cl2 + 2e–  2Cl–
F2 + 2e–  2F–
E° (volts)
–2.71
–1.66
–0.44
–0.28
+0.34
+0.80
+1.36
+2.87
15.
Which of the following would be the best reducing agent?
A) Cl2
B) F2
C) Na
D) Na+
E)
F–
16.
Silver will spontaneously reduce which of the following?
A) Fe2+
B) Co2+
C) Na+
D) Al3+
E)
none of these
17.
Determine the standard potential, E°, of a cell that employs the reaction
Co + Ag+  Co2+ +Ag
A) 1.08 V
B) 1.88 V
C) -1.08 V
D) -0.52 V
E) none of these
The standard potential for the reaction Zn + 2Ag +  Zn2+ + 2Ag is 1.56 V. Given that the standard reduction potential for Ag +
+ e–  Ag is 0.80 V, determine the standard reduction potential for Zn2+ + 2e–  Zn.
A) -0.76 V
B) 0.04 V
C) 0.76 V
D) -0.38 V
E)
none of these
Use the following to answer questions 19-20:
18.
The following questions refer to a galvanic cell that utilizes the following reaction (unbalanced):
(AuCl4)–(aq) + Cu(s)  Au(s) + Cl–(aq) + Cu2+(aq)
19.
Given the following information, determine the standard cell potential.
Species
Standard Reduction Potential (V)
Au3+(aq)
1.498
Cu2+(aq)
0.339
A)
B)
C)
D)
E)
1.159 V
1.837 V
1.979 V
1.462 V
2.102 V
20.
Determine the number of electrons transferred during the reaction (when balanced).
A) 2
B) 3
C) 4
D) 6
E)
9
21.
Choose the correct statement(s) given the following information:
Fe3+(aq) + e –  Fe2+(aq)
Fe(CN)63– + e–  Fe(CN) 64–
E° = 0.77 V
E° = 0.36 V
I.
II.
III.
Fe2+(aq) is more likely to be oxidized than Fe 2+ complexed to CN –.
Fe3+(aq) is more likely to be reduced than Fe 3+ complexed to CN –.
Complexation of Fe ions with CN – has no effect on their tendencies to
become oxidized or reduced.
A)
B)
C)
D)
E)
I only
II only
I and II
III only
None of these is true.
Use the following to answer questions 22-23:
Refer to the galvanic cell below (the contents of each half-cell are written beneath each compartment).
The standard reduction potentials are as follows:
MnO4– + 8H+ + 5e–  Mn2+ + 4H 2O
Cr2O72– +14H+ + 6e–  2 Cr3+ +7H2O
E = 1.51 V
E = 1.33 V
22.
What is the value of E°cell?
A) –0.18 V
B) 2.84 V
C) 0.18 V
D) 1.79 V
E)
2.29 V
23.
In the balanced cell reaction, what is the stoichiometric coefficient for H +?
A) 5
B) 6
C) 30
D) 22
E)
2
Use the following to answer questions 24-25:
Consider an electrochemical cell with a copper electrode immersed in 1.0 M Cu2+ and a silver electrode immersed in 1.0 M Ag+.
E° = 0.34 V
Cu2+ + 2e–  Cu
E° = 0.80 V
Ag+ + e–  Ag
24.
Calculate E° for this cell.
A) 1.48 V
B) 1.26 V
C) 1.14 V
D) 0.46 V
E)
none of these
25.
Which of the electrodes is the anode?
A) the copper electrode
B) the silver electrode
Use the following to answer questions 26-27:
Consider the galvanic cell shown below (the contents of each half-cell are written beneath each compartment).
The standard reduction potentials are as follows:
E° = –0.73 V
Cr 3+ + 3e–  Cr(s)
E° = +1.09 V
Br 2(aq) + 2e –  2Br –
26.
What is E° for this cell?
A) 1.82 V
B) 0.36 V
C) 4.75 V
D) 1.79 V
E)
4.40 V
27.
Which of the following statements about this cell is false?
A) This is a galvanic cell.
B) Electrons flow from the Pt electrode to the Cr electrode.
C) Reduction occurs at the Pt electrode.
D) The cell is not at standard conditions.
E)
To complete the circuit, cations migrate into the left half-cell and anions migrate into the right half-cell from the salt
bridge.
Use the following to answer questions 28-29:
The reaction Cr(s) + NO 3–(aq)  Cr3+(aq) + NO(g) takes place in acidic solution.
28.
How many electrons are transferred per mole of NO(g)?
A) 1
B) 2
C) 3
D) 4
E)
5
29.
What is the coefficient of H2O(l) in the balanced equation?
A) 1
B) 2
C) 3
D) 4
E)
5
Use the following to answer questions 30-33:
Refer to the galvanic cell below (the contents of each half-cell are written beneath each compartment).
The standard reduction potentials are as follows:
MnO4– + 8H+ + 5e–  Mn2+ + 4H 2O
Cr2O72– +14H+ + 6e–  2 Cr3+ +7H2O
E = 1.51 V
E = 1.33 V
30.
When current is allowed to flow, which species is oxidized?
A) Cr2O72–
B) Cr3+
C) MnO4–
D) Mn2+
E)
H+
31.
When current is allowed to flow, which species is reduced?
A) Cr2O72–
B) Cr3+
C) MnO4–
D) Mn2+
E)
H+
32.
In which direction do electrons flow in the external circuit?
A) left to right
B) right to left
C) No current flows; the cell is at equilibrium.
33.
How many electrons are transferred in the balanced reaction (that is, what will be the value of n in the Nernst equation)?
A) 5
B) 6
C) 30
D) 22
E)
2
Use the following to answer question 34:
In a common car battery, six identical cells each carry out the following reaction:
Pb + PbO2 + 2HSO 4– + 2H+  2PbSO 4 + 2H2O
34.
For such a cell, E° is 2.04 V. Calculate G° at 25°C.
A) -787 kJ
B) -98 kJ
C) -394 kJ
D) -197 kJ
E)
-0.121 kJ
35.
The reduction potentials for Au3+ and Ni2+ are as follows:
Au3+ + 3e–  Au E° = +1.50 V
Ni2+ + 2e–  Ni
E° = –0.23 V
Calculate G° (at 25°C) for the reaction
2Au3+ + 3Ni  3Ni2+ + 2Au
A)
B)
C)
D)
E)
36.
Consider the following reduction potentials:
Cu2+ + 2e–  Cu E° = +0.34 V
Pb 2+ + 2e–  Pb E° = –0.13 V
For a galvanic cell employing the Cu, Cu2+ and Pb, Pb2+ couples, calculate the maximum amount of work that would accompany
the reaction of 1 mol of lead under standard conditions.
A)
B)
C)
D)
E)
37.
–5.00  102 kJ
+5.00  102 kJ
–2140 kJ
+1.00  103 kJ
–1.00  103 kJ
–40.5 kJ
–45.3 kJ
–90.7 kJ
No work can be done. The system is at equilibrium.
none of these
The standard free energies of formation of several aqueous species are
kJ/mol
H+(aq)
0
H2O(l)
–237
CH3OH(aq)
–163
HCOOH(aq)
–351
e–
0
What is the standard reduction potential of methanoic acid in aqueous solution (that is, for HCOOH + 4H + + 4e–  CH3OH +
H2O)?
A)
B)
C)
D)
E)
+0.13 V
+0.17 V
+0.25 V
–0.13 V
–0.25 V
38.
In which of the following cases can E° be equal to zero?
I.
In any cell at equilibrium
II.
In a concentration cell
III. E° can never be equal to zero.
A)
B)
C)
D)
39.
In which of the following cases must E be equal to zero?
I.
In any cell at equilibrium
II.
In a concentration cell
III. E° can never be equal to zero.
A)
B)
C)
D)
40.
I only
II only
III
I and II
I only
II only
III
I and II
Consider the hydrogen–oxygen fuel cell where
H2(g) + O2(g)
H2O(l)
G° = –237.18 kJ/mol H2
Which of the following statements is(are) true?
I.
II.
III.
A)
B)
C)
D)
E)
41.
At standard conditions, the maximum work the fuel cell could do on the surroundings is 237.18 kJ/mol.
In the real world, the actual amount of useful work the cell can do is less than 237.18 kJ.
More energy is dissipated as waste heat in the fuel cell than in the reversible pathway.
I
II
III
I, II, and III
None of the statements is true.
A fuel cell designed to react grain alcohol with oxygen has the following net reaction:
C2H5OH(l) + 3O2(g)  2CO2(g) + 3H2O(l)
The maximum work that 1 mol of alcohol can yield by this process is 1320 kJ. What is the theoretical maximum voltage this cell
can achieve?
A)
B)
C)
D)
E)
42.
0.760 V
1.14 V
2.01 V
2.28 V
13.7 V
An excess of finely divided iron is stirred up with a solution that contains Cu 2+ ion, and the system is allowed to come to
equilibrium. The solid materials are then filtered off, and electrodes of solid copper and solid iron are inserted into the remaining
solution. What potential develops between these two electrodes at 25°C?
A) 0
B) –0.78 V
C) 0.592 V
D) 0.296 V
E)
Not enough information is given.
Use the following to answer questions 43-44:
You make a cell with a copper electrode in a solution of copper nitrate and a silver electrode in a solution of silver nitrat e.
E° = 0.34 V
Cu2+ + 2e–  Cu
+
–
E° = 0.80 V
Ag + e  Ag
43.
If you could increase the concentration of Ag +, which of the following would be true about the cell potential?
A) It would increase.
B) It would decrease.
C) It would remain constant.
D) This cannot be determined.
44.
If you could increase the concentration of Cu2+, which of the following would be true about the cell potential?
A) It would increase.
B) It would decrease.
C) It would remain constant.
D) This cannot be determined.
45.
A cell is set up with copper and lead electrodes in contact with CuSO 4(aq) and Pb(NO3)2(aq), respectively, at 25°C. The
standard reduction potentials are
Pb2+ + 2e–  Pb E° = –0.13 V
Cu2+ + 2e–  Cu
E° = +0.34 V
If sulfuric acid is added to the Pb(NO3)2 solution, forming a precipitate of PbSO4, the cell potential
A)
B)
C)
D)
increases.
decreases.
is unchanged.
It is impossible to tell what will happen.
46.
A concentration cell is constructed using two Ni electrodes with Ni 2+ concentrations of 1.64 M and 2.85  10–4 M in the two
half-cells. The reduction potential of Ni2+ is –0.23 V. Calculate the potential of the cell at 25°C.
A) +0.341 V
B) –0.222 V
C) –0.256 V
D) +0.111 V
E)
–0.0078 V
47.
The standard potential for the reaction A(s) + B3+(aq)
this reaction at 25°C?
A) 3.1  1025
B) 3.2  10–26
C) 17
D) –17
E)
0.015
A3+(aq) + B(s) is 0.50 V. What is the equilibrium constant K for
A concentration cell is constructed using two Co electrodes with Co 2+ concentrations of 0.20 M and 4.4  10–5 M in the two halfcells. Determine the standard reduction potential of Co 2+, given that the potential of the cell at 25°C is 0.108 V.
A) 0 V
B) +0.108 V
C) –0.108 V
D) +0.216 V
E)
This cannot be determined with the information given.
Use the following to answer question 49:
48.
Consider the galvanic cell shown below (the contents of each half-cell are written beneath each compartment).
The standard reduction potentials are as follows:
E° = –0.73 V
Cr 3+ + 3e–  Cr(s)
–
–
E°
= +1.09 V
Br 2(aq) + 2e  2Br
49.
What is the value of E for this cell at 25°C?
A) 2.21 V
B) 1.76 V
C) 2.12 V
D) 1.88 V
E)
0.59 V
Use the following to answer question 50:
Consider an electrochemical cell with a copper electrode immersed in 1.0 M Cu2+ and a silver electrode immersed in 1.0 M Ag+.
E° = 0.34 V
Cu2+ + 2e–  Cu
E° = 0.80 V
Ag+ + e–  Ag
50.
If [Cu2+]0 is 0.0034 M and [Ag+]0 is 0.34 M, calculate E.
A) 0.52 V
B) 0.59 V
C) 0.51 V
D) 0.41 V
E)
0.40 V
51.
For a reaction in a voltaic cell, both H° and S° are positive. Which of the following statements is true?
A) E°cell will increase with an increase in temperature.
B) E°cell will decrease with an increase in temperature.
C) E°cell will not change when the temperature increases.
D) G° > 0 for all temperatures.
E)
None of the above statements is true.
52.
Determine the equilibrium constant at 25°C for the reaction
Zn + Ni2+  Zn2+ + Ni
Zn2+ + 2e–  Zn
Ni-2+ + 2e–  Ni
A)
B)
C)
D)
E)
E° = -0.76 V
E° = -0.23 V
8.6  1017
9.3  108
4.1  103
6.4  10–6
none of these
53.
If a reducing agent X reacts with an oxidizing agent A2+ to give X2+ and A, and the equilibrium constant for the reaction is 1.0,
then what is the E° value for the oxidation–reduction reaction at 25°C?
A) 0.0 V
B) –1.0 V
C) 1.0 V
D) 0.030 V
E)
0.55 V
54.
A galvanic cell is constructed with copper electrodes and Cu 2+ in each compartment. In one compartment, [Cu2+] = 2.2  10–3 M,
and in the other compartment, [Cu2+] = 2.3 M. Calculate the potential for this cell at 25°C. The standard reduction potential for
Cu2+ is +0.34 V.
A) 0.43 V
B) –0.43 V
C) 0.089 V
D) –0.089 V
E)
0.77 V
55.
An excess of finely divided iron is stirred up with a solution that contains Cu2+ ion, and the system is allowed to come to
equilibrium. The solid materials are then filtered off, and electrodes of solid copper and solid iron are inserted into the remaining
solution. What is the value of the ratio [Fe2+]/[Cu2+] at 25°C?
A) 1
B) 0
C) 2.5  1026
D) 4.0  10–27
E)
none of these
Use the following to answer questions 56-57:
Consider an electrochemical cell that has a nickel electrode immersed in 1.0 M Ni2+ and a platinum electrode immersed in 0.010
M Co 2+.
E° = –0.28 V
Co 2+ + 2e–  Co
2+
–
E° = –0.23 V
Ni + 2e  Ni
56.
Calculate E for this cell.
A) 0.05 V
B) 0.11 V
C) 0.51 V
D) 0.56 V
E)
none of these
Calculate the concentration of Ni2+ if the cell is allowed to run to equilibrium at 25°C.
A) 1.1 M
B) 1.0 M
C) 0.020 M
D) 1.9  10–4 M
E)
none of these
Use the following to answer questions 58-60:
57.
Refer to the galvanic cell below (the contents of each half-cell are written beneath each compartment).
The standard reduction potentials are as follows:
MnO4– + 8H+ + 5e–  Mn2+ + 4H 2O
Cr2O72– +14H+ + 6e–  2 Cr3+ +7H2O
E = 1.51 V
E = 1.33 V
58.
What is the value of Q, the reaction quotient, for this cell reaction?
A) 6.7  1040
B) 1.5  10–41
C) 1.5  10–4
D) 6.7  103
59.
What is the cell potential at 25°C as read on the digital voltmeter?
A) 0.18 V
B) 2.58 V
C) 0.10 V
D) 0.59 V
E)
0.26 V
60.
What is the value of the equilibrium constant at 25°C for the net spontaneous cell reaction?
A) 7.3  10–11
B) 4.3  10–92
C) 91
D) 1.1  103
E)
2.3  1091
61.
Calculate E at 25°C for this cell, given the following data:
Ag+ + e–  Ag(s) E° = 0.80 V
Ni2+ + 2e–  Ni(s) E° = –0.23 V
Ksp for AgCl = 1.6  10–10
A)
B)
C)
D)
E)
62.
0.83 V
0.54 V
1.01 V
2.98 V
This cannot be determined from the data given
Use the following data to calculate the Ksp value at 25°C for PbSO4(s).
PbO2 + 4H + SO4 + 2e  PbSO4(s) + 2H 2O
PbO2 + 4H+ + 2e–  Pb 2+ + 2H2O
+
A)
B)
C)
D)
E)
63.
–
E°
+1.69
+1.46
2.57  10105
3.89  10–105
5.9  107
1.7  10–8
None of these is within 5% of the correct answer.
Calculate the solubility product of silver iodide at 25°C, given the following data:
E° (V)
–0.15
AgI(s) + e –  Ag(s) + I–
+0.54
I2(s) + 2e –  2I–
+0.80
Ag+ + e–  Ag(s)
A)
B)
C)
D)
E)
64.
2–
2.9  10–3
1.9  10–4
2.1  10–12
8.4  10–17
3.5  10–20
Why is aluminum protected from corrosion? (Note: The standard reduction potential for Al3+ is -1.66 V.)
A) Aluminum forms a protective oxide coating.
B) The oxidation of aluminum is not a favored process, as seen by the standard reduction potential for Al3+.
C) Oxygen and aluminum have no affinity for one another.
D) At least two of these are correct.
E)
Aluminum is not protected from corrosion.
If a constant current of 5.5 amperes is passed through a cell containing Cr3+ for 2.5 hour, how many grams of Cr will plate out
onto the cathode? (The atomic mass of Cr is 51.996 g/mol.)
A) 27 g
B) 0.15 g
C) 8.9 g
D) 80 g
E)
1.3 g
Use the following to answer question 66:
65.
In a common car battery, six identical cells each carry out the following reaction:
Pb + PbO2 + 2HSO 4– + 2H+  2PbSO 4 + 2H2O
66.
Suppose that to start a car on a cold morning, 136 amperes is drawn for 16.0 seconds from such a cell. How many grams of Pb
are consumed? (The atomic mass of Pb is 207.19 g/mol.)
A) 9.35 g
B) 2.34 g
C) 4.67 g
D) 0.00913 g
E)
0.428 g
Use the following to answer questions 67-68:
An antique automobile bumper is to be chrome plated. The bumper, which is dipped into an acidic Cr 2O72– solution, serves as a
cathode of an electrolytic cell. The atomic mass of Cr is 51.996; 1 faraday = 96,485 coulombs.
67.
If oxidation of H2O occurs at the anode, how many moles of oxygen gas will evolve for every 1.56  102 g of Cr(s) deposited?
A) 4.50 mol
B) 3.00 mol
C) 2.00 mol
D) 4.00 mol
E)
1.50 mol
68.
If the current is 21.4 amperes, how long will it take to deposit 1.72  102 g of Cr(s) onto the bumper?
A) 49.7 h
B) 24.9 h
C) 41.4 min
D) 15.8 h
E)
16.6 h
69.
Copper is electroplated from an aqueous CuSO4 solution. A constant current of 5.10 amp is applied by an external power
supply. How long will it take to deposit 4.08  102 g of Cu? The atomic mass of copper is 63.546 g/mol.
A) 67.5 h
B) 33.7 h
C) 2.44 h
D) 135.0 h
E)
101.2 h
70.
What quantity of charge is required to reduce 32.4 g of NiCl 2 to nickel metal? (1 faraday = 96,485 coulombs)
A) 2.41  104 C
B) 4.82  104 C
C) 1.07  105 C
D) 7.24  104 C
E)
9.65 104 C
71.
Electrolysis of a molten salt with the formula MCl, using a current of 3.86 amp for
16.2 min, deposits 1.52 g of metal. Identify the metal. (1 faraday = 96,485 coulombs)
A) Li
B) Na
C) K
D) Rb
E)
Ca
72.
If an electrolysis plant operates its electrolytic cells at a total current of 1.0  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) 2.2 h
B) 2.4 days
C) 55 min
D) 3.7 h
E)
1 year
73.
Nickel is electroplated from a NiSO4 solution. A constant current of 4.88 amp is applied by an external power supply. How long
will it take to deposit 2.22  102 g of Ni? (The atomic mass of Ni is 58.69 g/mol.)
A) 41.5 h
B) 20.8 h
C) 1.38 h
D) 62.3 h
E)
24.9 min
74.
A solution of MnO42– is electrolytically reduced to Mn3+. A current of 9.10 amp is passed through the solution for 16.6 minutes.
What is the number of moles of Mn3+ produced in this process? (1 faraday = 96,486 coulombs)
A) 0.0939 mol
B) 0.000522 mol
C) 0.0235 mol
D) 0.0313 mol
E)
0.0470 mol
75.
How many seconds would it take to deposit 21.40 g of Ag (atomic mass = 107.87) from a solution of AgNO 3 using a current of
10.00 amp?
A) 9649 s
B) 4825 s
C) 3828 s
D) 1914 s
E)
none of these
76.
Gold (atomic mass = 197 g/mol) is plated from a solution of chlorauric acid, HAuCl4; it deposits on the cathode. Calculate the
time it takes to deposit 0.70 g of gold, passing a current of 0.10 amperes. (1 faraday = 96,485 coulombs)
A) 0.95 h
B) 2.9 h
C) 3.8 h
D) 0.0019 days
E)
1.9 h
77.
An electrolytic cell process involves plating Zr(s) from a solution containing Zr4+. If 5.80 amp is run through this mixture for
1.86 h, what mass of Zr is plated?
A) 36.7 g
B) 0.153 g
C) 0.101 g
D) 9.18 g
E)
none of these
78.
Gold is produced electrochemically from an aqueous solution of Au(CN)2– containing an excess of CN–. Gold metal and oxygen
gas are produced at the electrodes. How many moles of O 2 will be produced during the production of 1.00 mol of gold?
A) 0.25 mol
B) 0.50 mol
C) 1.00 mol
D) 3.56 mol
E)
4.00 mol
Answer Key
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
C
B
C
C
B
C
D
A
D
C
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
A
C
D
A
C
E
A
A
A
D
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
B
C
D
D
A
A
B
C
B
B
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
C
B
C
C
E
C
A
B
A
D
41.
42.
43.
44.
45.
46.
47.
48.
49.
50.
B
A
A
B
A
D
E
E
D
C
51.
52.
53.
54.
55.
56.
57.
58.
59.
60.
A
A
A
C
C
B
C
B
E
E
61.
62.
63.
64.
65.
66.
67.
68.
69.
70.
B
D
D
A
C
B
A
B
A
B
71.
72.
73.
74.
75.
76.
77.
78.
C
A
A
D
D
B
D
A