B)
C)
D)
E)
none of these
69. For a reaction in a voltaic cell both H° and S° are positive. Which of the following
statements is true?
A)
cell will increase with an increase in temperature.
B)
cell will decrease with an increase in temperature.
C)
cell will not change when the temperature increases.
D)
G° > 0 for all temperatures.
E)
None of the above statements is true.
70. 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
71. The standard free energies of formation of several species are:
kJ/mol
H+(aq)
0
H2O(l)
–237.0
CH3OH(aq)
–163.0
HCOOH(aq)
–351.2
e–
0
What is the standard reduction potential of methanoic acid in aqueous solution (i.e., for
HCOOH + 4H+ + 4e– → CH3OH + H2O)?
A)
0.126 V
B)
0.506 V
C)
–0.718 V
D)
–0.126 V
E)
1.946 V
72. 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 one mole of alcohol can yield by this process is 1320 kJ. What is the
theoretical maximum voltage this cell can achieve?
A)
0.760 V
B)
1.14 V
C)
2.01 V
D)
2.28 V
E)
13.7 V
73. Consider the following reduction potentials:
Cu2+ + 2e– → Cu
= 0.342 V
Pb2+ + 2e– → Pb
= –0.130 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 one mole of lead under standard
conditions.
A)
–40.9 kJ
B)
–45.5 kJ
C)
–91.1 kJ
D)
No work can be done. The system is at equilibrium.
E)
None of these.
74. 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
75. For a particular reaction in a galvanic (voltaic) cell S° is negative. Which of the following
statements is true?
A)
will increase with an increase in temperature.
B)
will decrease with an increase in temperature.
C)
will not change when the temperature increases.
D)
G° > 0 for all temperatures.
E)
None of the above statements is true.
76. Under standard conditions, which of the following operations results in a spontaneous
chemical reaction taking place?
A)
A piece of aluminum metal is placed in an aqueous solution of potassium nitrate.
B)
Iodine crystals are added to an aqueous solution of sodium chloride.
C)
A piece of silver metal is placed in an aqueous solutions of copper(II) nitrate.
D)
Chlorine gas is bubbled through an aqueous solution of sodium bromide.
E)
At least two of the above (A-D) result in a spontaneous chemical reaction.
77. A common car battery consists of six identical cells, each of which carries out the reaction:
Pb + PbO2 + 2HSO4– + 2H+ → 2PbSO4 + 2H2O
The value of for such a cell is 2.039 V. Calculate G° at 25 °C for the reaction.
A)
–196.7 kJ
B)
–98.37 kJ
C)
–393.5 kJ
D)
–786.9 kJ
E)
–590.2 kJ
78. 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)
–232 kJ/mol
B)
116 kJ/mol
C)
232 kJ/mol
D)
464 kJ/mol
E)
–464 kJ/mol
Consider an electrochemical cell with a zinc electrode immersed in 1.0 M Zn2+ and a nickel
electrode immersed in 0.10 M Ni2+.
Zn2+ + 2e- → Zn
° = –0.76 V
Ni2+ + 2e- → Ni
° = –0.23 V
79. Calculate the concentration of Ni2+ if the cell is allowed to run to equilibrium at 25°C.
A)
1.10 M
B)
0.20 M
C)
0.10 M
D)
0 M
E)
none of these
80. Calculate
at 25°C for the cell shown below, given the following data:
Ksp for AgCl = 1.6 10–10
A)
0.83 V
B)
0.54 V
C)
1.01 V
D)
2.98 V
E)
cannot be determined from the data given
81. The following question refers to the following system:
Ni Ag
3Ag(s) + NO3–(aq) + 4H+(aq) → 3Ag+(aq) + NO(g) + 2H2O(l)
Anode reaction:
Ag → Ag+(aq) + 1e–
° = –0.7990 V
Cathode reaction:
NO3–(aq) + 4H+(aq) + 3e– → NO(g) + 2H2O(l)
° = 0.9636 V
Determine the equilibrium constant at 25°C.
A)
B)
C)
D)
E)
3.117
82. A galvanic cell consists of a left compartment with a tin electrode in contact with 0.1 M
Sn(NO3)2(aq) and a right compartment with a lead electrode in contact with 1 10–3 M
Pb(NO3)2(aq). The relevant reduction potentials are:
Pb2+ + 2e– → Pb
° = –0.13 V
Sn2+ + 2e– → Sn
° = –0.14 V
When this cell is allowed to discharge spontaneously at 25°C, which of the following
statements is true?
A)
Electrons will flow from left to right through the wire.
B)
Pb2+ ions will be reduced to Pb metal.
C)
The concentration of Sn2+ ions in the left compartment will increase.
D)
The tin electrode will be the cathode.
E)
No noticeable change will occur, because the cell is at equilibrium.
83. Consider the galvanic cell shown below (the contents of each half-cell are written beneath
each compartment):
0.50 M Br2
0.20 M Cr3+
0.10 M Br–
6.097 102
2.965 1089
4.412 10−9
2.266 108
Pt Cr
The standard reduction potentials are as follows:
Cr3+(aq) + 3e– → Cr(s)
° = –0.733 V
Br2(aq) + 2e– → 2Br–(aq)
° = +1.090 V
What is the value of
for this cell at 25°C?
A)
1.759 V
B)
1.823 V
C)
1.837 V
D)
1.887 V
E)
2.207 V
84. Consider an electrochemical cell with a zinc electrode immersed in a solution of Zn2+ and a
silver electrode immersed in a solution of Ag+.
Zn2+ + 2e– → Zn
° = –0.76 V
Ag+ + e– → Ag
° = 0.80 V
If is 0.050 M and is 11.26 M, calculate
.
A)
1.46 V
B)
1.76 V
C)
1.36 V
D)
1.66 V
E)
1.63 V
85. Consider an electrochemical cell with a zinc electrode immersed in 1.0 M Zn2+ and a nickel
electrode immersed in 0.39 M Ni2+.
Zn2+ + 2e– → Zn
° = –0.76 V
Ni2+ + 2e– → Ni
° = –0.23 V
Calculate
for this cell.
A)
0.54 V
B)
0.52 V
C)
0.51 V
D)
0.53 V
E)
0.98 V
86. A cell is set up with copper and lead electrodes in contact with CuSO4(aq) and
Pb(NO3)2(aq), respectively, at 25°C. The standard reduction potentials are:
Pb2+ + 2e– → Pb
° = –0.13 V
Cu2+ + 2e– → Cu
° = +0.34 V
If sulfuric acid is added to the Pb(NO3)2 solution, forming a precipitate of PbSO4, the cell
potential:
A)
increases
B)
decreases
C)
is unchanged
D)
can’t tell what will happen
E)
none of these
87. A concentration cell is constructed using two Ni electrodes with Ni2+ concentrations of 1.0
M and 1.00 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)
–0.368 V
B)
+0.132 V
C)
–0.132 V
D)
+0.118 V
E)
+0.0592 V
88. The standard potential for the reaction A + B C + D is 1.50 volts. The equilibrium
constant K for this reaction at 25°C is:
A)
2.5 1025
B)
4.0 10–26
C)
25.4
D)
–25.4
E)
not enough information given
89. 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 Sn + Ni2+
A)
B)
35
C)
5.9
3.6 1012
D)
E)
90. 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?
The following standard reduction potentials apply:
Fe2+(aq) + 2e– → Fe(s)
° = –0.44 V
Cu2+(aq) + 2e– → Cu(s)
° = +0.34 V
A)
1
B)
0
C)
2.5 1026
D)
4.4 10–27
E)
none of these
91. 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
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 given
92. The equilibrium constant at 25°C for the reaction Al + 3Cu2+ 2Al3+ + 3Cu is
approximately
A)
10203
B)
1034
C)
1068
D)
10–203
E)
none of these
8.3 10−4
1.2 103
93. A concentration cell is constructed with copper electrodes and Cu2+ in each compartment. In
one compartment, the [Cu2+] = 1.0 10–3 M and in the other compartment, the [Cu2+] = 2.0
M. Calculate the potential for this cell at 25°C. The standard reduction potential for Cu2+ is
+0.34 V.
A)
0.44 V
B)
–0.44 V
C)
0.098 V
D)
–0.098 V
E)
0.78 V
94. Calculate the solubility product of silver iodide at 25°C given the following data:
°(V)
AgI(s) + e– → Ag(s) + I–
–0.15
I2(s) + 2e– → 2I–
+0.54
Ag+ + e– → Ag(s)
+0.80
A)
2.9 10–3
B)
1.9 10–4
C)
2.1 10–12
D)
8.4 10–17
E)
6.1 10–26
95. Using the following data to calculate Ksp for PbSO4.
°
PbO2 + 4H+ + SO42– + 2e– → PbSO4(s) + 2H2O
+1.69
PbO2 + 4H+ + 2e– → Pb2+ + 2H2O
+1.46
A)
4.0 10106
B)
2.5 10–107
C)
5.9 107
D)
1.7 10–8
E)
None of these is within 5% of the correct answer.
96. In which of the following cases must
be equal to zero?
A)
In any cell at equilibrium.
B)
In a concentration cell.
C)
can never be equal to zero.
D)
Choices A and B are both correct.
E)
None of these.
97. Which of the following statements is/are correct?
A)
The value of
° is equal to zero in a concentration cell, and the value of
is equal
to zero in any cell at equilibrium.
B)
The value of
° can be equal to zero in a concentration cell, and the value of
must
be equal to zero in a concentration cell.
C)
The values of
° and
are equal to zero in any cell at equilibrium.
D)
° can never be equal to zero.
E)
At least two of the above choice (A-D) are correct.
98. Which of the following statements is true about a voltaic cell for which
°cell = 1.00 V?
A)
It has G° > 0.
B)
The system is at equilibrium.
C)
It has K = 1.
D)
The cathode is at a higher energy than the anode.
E)
The reaction is spontaneous.
99. If a reducing agent M reacts with an oxidizing agent N+ to give M+ and N, and the
equilibrium constant for the reaction is 1.6, then what is the
° value for the oxidation-
reduction reaction?
A)
0.012 V
B)
–0.012 V
C)
0.0060 V
D)
–0.0060 V
E)
0.024 V
You make a cell with an aluminum electrode in a solution of aluminum nitrate and a zinc
electrode in a solution of zinc nitrate.
100. If you could increase the concentration of Zn2+, which of the following is true about the cell
potential?
A)
It would increase.
B)
It would decrease.
C)
It would remain constant.
D)
Cannot be determined.
E)
None of these (A-D).
101. If you could increase the concentration of Al3+, which of the following is true about the cell
potential?
A)
It would increase.
B)
It would decrease.
C)
It would remain constant.
D)
Cannot be determined.
E)
None of these (A-D).
102. A concentration cell is constructed using two metal (M) electrodes with M2+ concentrations
of 0.10 M and 1.00 10–5 M in the two half-cells. Determine the reduction potential of M2+
given that the potential of the cell at 25°C is 0.118 V.
A)
0 V
B)
+0.118 V
C)
–0.118 V
D)
Cannot be determined with the information given.
E)
None of the above.
103. 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)
0.282 V
B)
0.491 V
C)
0.460 V
D)
0.473 V
E)
0.494 V