104. 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.
105. 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)
177
B)
131
C)
D)
E)
106. In order to determine the identity of a particular lanthanide metal Sm, a voltaic cell is
constructed at 25°C with the anode consisting of the lanthanide metal as the electrode
immersed in a solution of 0.0819 M SmCl3, and the cathode consisting of a copper electrode
immersed in a 1.00 M Cu(NO3)2 solution. The two half-reactions are as follows:
Sm(s) → Sm3+(aq) + 3e–
Cu2+(aq) + 2e– → Cu(s)
The potential measured across the cell is 2.67 V. What is the identity of the metal?
Reduction Half-Reaction
° (V)
Cu2+(aq) + 2e– → Cu(s)
0.34
Ce3+(aq) + 3e– → Ce(s)
–2.336
Dy3+(aq) + 3e– → Dy(s)
–2.295
Eu3+(aq) + 3e– → Eu(s)
–1.991
Gd3+(aq) + 3e– → Gd(s)
–2.279
Sm3+(aq) + 3e– → Sm(s)
–2.304
A)
Ce
B)
Eu
C)
Dy
D)
Sm
1.25 10−2
7.63 10−3
5.65 10−3
E)
Gd
107. 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)
The cell reaction is spontaneous with a cell potential of 4.81 mV.
B)
The cell reaction is spontaneous with a cell potential of 0.418 mV.
C)
The cell reaction is nonspontaneous with a cell potential of –0.418 mV.
D)
The cell reaction is nonspontaneous with a cell potential of –4.81 mV.
E)
The cell reaction is spontaneous with a cell potential of 0.340 V.
108. What is the potential at 25°C for the following cell?
Cr | Cr3+(0.015 M) || Ag+(0.00025 M) | Ag
Cr3+ + 3e–Cr
° = –0.73 V
Ag+ + e–Ag
° = 0.80 V
A)
2.09 V
B)
1.35 V
C)
0.95 V
D)
1.71 V
E)
1.49 V
109. Concentration cells work because standard reduction potentials are dependent on
concentration.
110. 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 true?
A)
At standard conditions, the maximum work the fuel cell could do on the
surroundings is 237.18 kJ/mol.
B)
In the real world, the actual amount of useful work the cell can do is less than
237.18 kJ.
C)
More energy is dissipated as waste heat in the fuel cell than in the reversible
pathway.
D)
A, B, and C are all true.
E)
A, B, and C are all false.
111. Which type of battery has been designed for use in space vehicles?
A)
lead storage
B)
alkaline dry cell
C)
mercury cells
D)
fuel cells
E)
silver cells
112. Which of the following statements about batteries is false?
A)
A battery is a group of galvanic cells connected in series.
B)
Lead storage batteries contain lead at the anode and lead coated with lead dioxide
at the cathode.
C)
The alkaline dry cell battery can last longer than a nickel-cadmium battery.
D)
A fuel cell is a galvanic cell for which the reactants are continuously supplied.
E)
Dry cell batteries are used in tape players and portable radios.
113. Which of the following statements about corrosion is false?
A)
Patina is the layer of tarnish that gives silver a richer appearance.
B)
The oxidation of most metals by oxygen is spontaneous.
C)
Most metals will develop a thin oxide coating, which protects their internal atoms
from oxidation.
D)
A car exposed to the elements will rust faster in the Midwest than in Arizona.
E)
All of these are true.
114. Which of the following statements is false?
A)
Stainless steel contains chromium and nickel, which form protective oxide
coatings.
B)
Galvanized steel is coated with zinc to form an oxide coating.
C)
Cathodic protection is a method used to protect steel in buried tanks and pipelines.
D)
Chromium and tin are often used to plate steel by forming a durable oxide coating.
E)
All of these are true.
115. How many faradays are involved in conversion of a mole of to ?
A)
1
B)
2
C)
3
D)
4
E)
5
116. 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
117. A common car battery consists of six identical cells each of which carries out the reaction:
Pb + PbO2 + 2HSO4– + 2H+ → 2PbSO4 + 2H2O
Suppose that in starting a car on a cold morning a current of 125 amperes is drawn for 18.4
seconds from a cell of the type described above. How many grams of Pb would be
consumed? (The atomic weight of Pb is 207.19.)
A)
4.94 g
B)
2.47 g
C)
g
D)
g
E)
g
An antique automobile bumper is to be chrome plated. The bumper, which is dipped into an
acidic solution, serves as a cathode of an electrolytic cell. The atomic mass of Cr is
51.996; 1 faraday = 96,485 coulombs.
7.29 10−3
1.58 10−4
1.19 10−2
118. 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
119. 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
120. 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
121. What quantity of charge is required to reduce 27.8 g of CrCl3 to chromium metal?
(1 faraday = 96,485 coulombs)
A)
C
B)
C
C)
C
D)
C
E)
none of these
5.08 104
8.05 102
2.68 102
122. 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
123. If a constant current of 5.0 amperes is passed through a cell containing Cr3+ 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
B)
g
C)
3.2 g
D)
29 g
E)
g
124. 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
125. Nickel is electroplated from a NiSO4 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
9.0 10−4
6.2 10−2
126. A solution of MnO42– is electrolytically reduced to Mn3+. A current of 8.07 amp is passed
through the solution for 15.0 minutes. What is the number of moles of Mn3+ produced in this
process? (1 faraday = 96,485 coulombs)
A)
0.0753
B)
0.226
C)
D)
0.0251
E)
127. 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?
A)
s
B)
s
C)
s
D)
s
E)
s
128. Gold (atomic mass = 197.0) is plated from a solution of chloroauric acid, HAuCl4; it
deposits on the cathode. Calculate the time it takes to deposit 0.30 gram of gold, passing a
current of 0.10 amperes. (1 faraday = 96,485 coulombs)
A)
12 hours
B)
1.2 hours
C)
24 minutes
D)
8.2 minutes
E)
none of these
129. An unknown metal (M) is electrolyzed. It took 74.1 s for a current of 2.00 amp to plate
0.107 g of the metal from a solution containing M(NO3)3. Identify the metal.
A)
La
B)
Bi
C)
Ga
D)
Cu
E)
Rh
4.18 10−4
1.67 10−3
3.26 103
1.63 103
5.43 102
130. 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 O2 will be produced during the production of 1.00 mole of gold?
A)
0.25
B)
0.50
C)
1.00
D)
3.56
E)
4.00
131. What mass of Ti(s) may be deposited from an aqueous TiCl2 solution if a current of 2.50 A
is applied to the solution for 365 s? (
°red(Ti2+/Ti) = –1.63 V, F = 96485 C/mol)
A)
0.453 g
B)
0.906 g
C)
0.369 g
D)
0.226 g
E)
0.139 g
132. What mass of chromium could be deposited by electrolysis of an aqueous solution of
Cr2(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
133. Which of the following are incorrectly paired?
A)
Alumina – pure aluminum oxide
B)
Downs cell – electrolyzes molten sodium chloride
C)
Mercury cell – used in preventing contamination of NaOH by NaCl
D)
Hall-Heroult process – uses cryolite in production of aluminum
E)
All of these are correct.
134. Which of the following used to be more precious than gold or silver, due to difficulties
refining it?
A)
copper
B)
aluminum
C)
tin
D)
zinc
E)
iron
135. What are the products of the chlor-alkali process?
A)
sodium and sodium chloride
B)
sodium chloride and chlorine
C)
sodium and chlorine
D)
sodium hydroxide and chlorine
E)
aluminum and cryolite
136. Balance the following equation: Cr2O72– + I– → Cr3+ + IO3– (acid)
137. Balance the following equation: Zn + As2O3 → AsH3 + Zn2+ (acid)
138. Balance the following equation: MnO4– + Br– → MnO2 + BrO3– (base)
139. Balance the following equation: Bi(OH)3 + SnO22– → Bi + SnO32– (base)
140. Consider a galvanic cell with a zinc electrode immersed in 1.0 M Zn2+ and a silver electrode
immersed in 1.0 M Ag+.
Zn2+ + 2e– → Zn
° = –0.76 V
Ag+ + e– → Ag
° = 0.80 V
Which of the electrodes is the anode?