Electrochemistry
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Transcript Electrochemistry
Chapter 20
Standardized Test Preparation
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• Multiple Choice
• Short Answer
• Extended Response
Chapter 20
Standardized Test Preparation
Multiple Choice
1. The electrode at which reduction occurs is
A. always the anode.
B. always the cathode.
C. either the anode or the cathode.
D. always the half-cell.
Chapter 20
Standardized Test Preparation
Multiple Choice
1. The electrode at which reduction occurs is
A. always the anode.
B. always the cathode.
C. either the anode or the cathode.
D. always the half-cell.
Chapter 20
Standardized Test Preparation
Multiple Choice
2. Refer to the table of standard reduction potentials
below. A voltaic cell contains a strip of zinc metal in
a solution containing zinc ions in one half-cell. The
second is a strip of tin metal in a solution containing
tin ions. When this cell operates,
A. Sn is oxidized and Zn2+ is reduced.
B. Sn is reduced and Zn2+ is oxidized.
C. Sn2+ is oxidized and Zn is reduced.
D. Sn2+ is reduced and Zn is oxidized.
Chapter 20
Standardized Test Preparation
Multiple Choice
2. Refer to the table of standard reduction potentials
below. A voltaic cell contains a strip of zinc metal in
a solution containing zinc ions in one half-cell. The
second is a strip of tin metal in a solution containing
tin ions. When this cell operates,
A. Sn is oxidized and Zn2+ is reduced.
B. Sn is reduced and Zn2+ is oxidized.
C. Sn2+ is oxidized and Zn is reduced.
D. Sn2+ is reduced and Zn is oxidized.
Chapter 20
Standardized Test Preparation
Multiple Choice
3. When a rechargeable cell is being recharged, the cell
acts as a(n)
A. fuel cell.
B. electrolytic cell.
C. voltaic cell.
D. Leclanche cell.
Chapter 20
Standardized Test Preparation
Multiple Choice
3. When a rechargeable cell is being recharged, the cell
acts as a(n)
A. fuel cell.
B. electrolytic cell.
C. voltaic cell.
D. Leclanche cell.
Chapter 20
Standardized Test Preparation
Multiple Choice
4. Refer to the table of standard reduction potentials below. The
standard potential of the cell Sn|Sn2+||Cr3+|Cr is −0.60 V. What is
the standard reduction potential of the Cr3+/Cr electrode?
A. +0.88 V
C. −0.88 V
B. +0.74 V
D. −0.74 V
Half-cell reaction
Au3 3e–
Cu2 2e–
Fe2 2e–
Sn2 2e–
Zn2 2e–
Mg2 2e–
Au
Cu
Fe
Sn
Zn
Mg
Standard Reduction potential, E0 (in volts)
+1.50
+0.34
-0.41
-0.14
-0.76
-2.37
Chapter 20
Standardized Test Preparation
Multiple Choice
4. Refer to the table of standard reduction potentials below. The
standard potential of the cell Sn|Sn2+||Cr3+|Cr is −0.60 V. What is
the standard reduction potential of the Cr3+/Cr electrode?
A. +0.88 V
C. −0.88 V
B. +0.74 V
D. −0.74 V
Half-cell reaction
Au3 3e–
Cu2 2e–
Fe2 2e–
Sn2 2e–
Zn2 2e–
Mg2 2e–
Au
Cu
Fe
Sn
Zn
Mg
Standard Reduction potential, E0 (in volts)
+1.50
+0.34
-0.41
-0.14
-0.76
-2.37
Chapter 20
Standardized Test Preparation
Multiple Choice
5. Refer to the table of reduction potentials below. Which
metal, Zn or Au, can reduce Sn2+ ions to Sn metal
when placed in an aqueous solution of Sn2+ ions?
A. Zn
B. Au
C. Both Zn and Au can reduce Sn2+ ions
D. Neither Zn or Au can reduce Sn2+ ions
Chapter 20
Standardized Test Preparation
Multiple Choice
5. Refer to the table of reduction potentials below. Which
metal, Zn or Au, can reduce Sn2+ ions to Sn metal
when placed in an aqueous solution of Sn2+ ions?
A. Zn
B. Au
C. Both Zn and Au can reduce Sn2+ ions
D. Neither Zn or Au can reduce Sn2+ ions
Chapter 20
Standardized Test Preparation
Multiple Choice
6. When silver is electroplated onto another metal,
Ag+ is
A. oxidized at the anode.
B. reduced at the anode.
C. oxidized at the cathode.
D. reduced at the cathode.
Chapter 20
Standardized Test Preparation
Multiple Choice
6. When silver is electroplated onto another metal,
Ag+ is
A. oxidized at the anode.
B. reduced at the anode.
C. oxidized at the cathode.
D. reduced at the cathode.
Chapter 20
Standardized Test Preparation
Multiple Choice
7. Which metal would best provide cathodic protection
from corrosion for an iron bridge?
A. Au
B. Sn
C. Cu
D. Mg
Chapter 20
Standardized Test Preparation
Multiple Choice
7. Which metal would best provide cathodic protection
from corrosion for an iron bridge?
A. Au
B. Sn
C. Cu
D. Mg
Chapter 20
Standardized Test Preparation
Short Answer
8. In the production of aluminum by the Hall-Héroult
process, is the aluminum metal produced at the
cathode or the anode?
Chapter 20
Standardized Test Preparation
Short Answer
8. In the production of aluminum by the Hall-Héroult
process, is the aluminum metal produced at the
cathode or the anode?
Answer: Since the aluminum metal is produced by the
reduction of Al3+ ions to aluminum metal, the metal is
produced at the cathode. Reduction always occurs at
the cathode.
Chapter 20
Standardized Test Preparation
Short Answer
9. The reduction potential for nitric acid is 0.96 V
(reduction half-reaction is
NO3– + 4H 3e– NO 2H2O ). If gold (Au) is
placed in a beaker of 1 M nitric acid, will the gold
dissolve?
Chapter 20
Standardized Test Preparation
Short Answer
9. The reduction potential for nitric acid is 0.96 V
(reduction half-reaction is
NO3– + 4H 3e– NO 2H2O ). If gold (Au) is
placed in a beaker of 1 M nitric acid, will the gold
dissolve?
Answer: The Au will not dissolve because its reduction
potential is +1.50 V. Hence, for Au to be oxidized
(dissolved), there needs to be at least 1.50 V from the
reduction of nitric acid and there is only 0.96 V.
Chapter 20
Standardized Test Preparation
Extended Response
10. Given a voltaic cell consisting of a gold electrode in a
gold nitrate solution in one half-cell and a zinc
electrode in a zinc nitrate solution in the other half-cell,
what occurs once the wire is connected to both
electrodes?
Chapter 20
Standardized Test Preparation
Extended Response
10. Given a voltaic cell consisting of a gold electrode in a gold nitrate
solution in one half-cell and a zinc electrode in a zinc nitrate
solution in the other half-cell, what occurs once the wire is
connected to both electrodes?
Answer: The gold ions are reduced and zinc is oxidized because
gold has a higher reduction potential than zinc does. The zinc
electrode dissolves as electrons travel from the anode through
the wire down the gold electrode to the gold nitrate solution. As
the gold ions are reduced, gold atoms are deposited onto the
gold electrode, which is the cathode. To keep the charge
balanced, nitrate ions move from the anode to the cathode
through the porous barrier. Depending on the type of porous
barrier, gold ions could move from the cathode to the anode to
keep the charge balanced.
Chapter 20
Standardized Test Preparation
Extended Response
11. If pure water is placed in a beaker with wires
connected to a cathode and anode and electrical
voltage is applied, will electrolysis of water occur?
Explain your answer.
Chapter 20
Standardized Test Preparation
Extended Response
11. If pure water is placed in a beaker with wires
connected to a cathode and anode and electrical
voltage is applied, will electrolysis of water occur?
Explain your answer.
Answer: Significant electrolysis of water will not occur for
pure water because it does not contain enough ions
for current to flow. An electrolyte needs to be added.
The electrolytes are not part of the half-cell reactions,
but they are needed for the transfer of charge.