Name:__________________
Period:______
Voltaic/Electrolytic Cells
1. A voltaic cell spontaneously converts chemical
energy to
A) electrical energy
C) mechanical energy
B) geothermal energy D) nuclear energy
2. When a voltaic cell operates, ions move through the
A) anode
B) cathode
C) salt bridge
D) external circuit
6. Which energy conversion must occur in an operating
electrolytic cell?
A)
B)
C)
D)
electrical energy to chemical energy
electrical energy to nuclear energy
chemical energy to electrical energy
chemical energy to nuclear energy
7. The diagram below represents an operating
electrochemical cell and the balanced ionic equation
for the reaction occurring in the cell.
3. Given the balanced ionic equation representing the
reaction in an operating voltaic cell:
Zn(s) + Cu 2+(aq) ® Zn2+(aq) + Cu(s)
The flow of electrons through the external circuit in
this cell is from the
A)
B)
C)
D)
Cu anode to the Zn cathode
Cu cathode to the Zn anode
Zn anode to the Cu cathode
Zn cathode to the Cu anode
4. Reduction occurs at the cathode in
A)
B)
C)
D)
electrolytic cells, only
voltaic cells, only
both electrolytic cells and voltaic cells
neither electrolytic cells nor voltaic cells
5. A student collects the materials and equipment below
to construct a voltaic cell:
• two 250-mL beakers
• wire and a switch
• one strip of magnesium
• one strip of copper
• 125 mL of 0.20 M Mg(NO 3) 2(aq)
• 125 mL of 0.20 M Cu(NO 3) 2(aq)
Which additional item is required for the construction
of the voltaic cell?
A) an anode
B) a battery
C) a cathode
D) a salt bridge
Which statement identifies the part of the cell that
conducts electrons and describes the direction of
electron flow as the cell operates?
A) Electrons flow through the salt bridge from the
Ni(s) to the Zn(s).
B) Electrons flow through the salt bridge from the
Zn(s) to the Ni(s).
C) Electrons flow through the wire from the Ni(s) to
the Zn(s).
D) Electrons flow through the wire from the Zn(s) to
the Ni(s).
8. Given the balanced equation representing a reaction
occurring in an electrolytic cell:
2NaCl( )
2Na( ) + Cl 2(g)
Where is Na( ) produced in the cell?
A)
B)
C)
D)
at the anode, where oxidation occurs
at the anode, where reduction occurs
at the cathode, where oxidation occurs
at the cathode, where reduction occurs
Base your answers to questions 9 through 11 on
the information below.
Metallic elements are obtained from their ores by reduction. Some metals, such as zinc, lead, iron,
and copper, can be obtained by heating their oxides with carbon.
More active metals, such as aluminum, magnesium, and sodium, can not be reduced by carbon.
These metals can be obtained by the electrolysis of their molten (melted) ores. The diagram below
represents an incomplete cell for the electrolysis of molten NaCl. The equation below represents the
reaction that occurs when the completed cell operates.
9. Write a balanced half-reaction equation for the reduction of the iron ions in iron(III) oxide to iron
atoms.
10. Identify one metal from the passage that is more active than carbon and one metal from the passage
that is less active than carbon.
11. Identify the component required for the electrolysis of molten NaCl that is missing from the cell
diagram.
Base your answers to questions 12 through 14 on the information below.
The diagram below represents an operating electrolytic cell used to plate silver
onto a nickel key. As the cell operates, oxidation occurs at the silver electrode and the
mass of the silver electrode decreases.
12. Explain, in terms of Ag atoms and Ag + (aq) ions, why the mass of the silver electrode decreases as
the cell operates.
13. State the purpose of the power source in the cell.
14. Identify the cathode in the cell.
Base your answers to questions 15 through 17 on the information below.
The diagram below represents an operating voltaic cell at 298 K and 1.0 atmosphere in a laboratory
investigation. The reaction occurring in the cell is represented by the balanced ionic equation below.
15. Write a balanced half-reaction equation for the reduction that occurs in this cell.
16. Determine the total number of moles of Ni2+(aq) ions produced when 4.0 moles of Ag+(aq) ions
completely react in this cell
17. Identify the anode in this cell.
Base your answers to questions 18 and 19 on the information below.
The diagram below shows a system in which water is being decomposed into oxygen gas
and hydrogen gas. Litmus is used as an indicator in the water. The litmus turns red in test tube 1
and blue in test tube 2.
0006467
The oxidation and reduction occurring in the test tubes are represented by the balanced
equations below.
–
Test tube 1: 2H2O( ) ® O2(g) + 4H+(aq) + 4e
Test tube 2: 4H2O( ) + 4e– ® 2H2(g) + 4OH–(aq)
18. Determine the change in oxidation number of oxygen during the reaction in test tube 1.
19. Identify the information in the diagram that indicates this system is an electrolytic cell.
20. Base your answer to the following question on the information below.
A voltaic cell with magnesium and copper electrodes is shown in the diagram below. The
copper electrode has a mass of 15.0 grams.
When the switch is closed, the reaction in the cell begins. The balanced ionic equation for the
reaction in the cell is shown below the cell diagram. After several hours, the copper electrode is
removed, rinsed with water, and dried. At this time, the mass of the copper electrode is greater
than 15.0 grams.
State the directions of electron flow through the wire between the electrodes when the switch is
closed.
Answer Key
Voltaic/Electrolytic Cells
1.
A
18.
–2 to 0
2.
C
19.
3.
C
4.
C
5.
D
6.
A
7.
D
• A battery is part of
the cell and is
providing energy
that causes the
reaction. •
Electricity is used to
operate the cell.
8.
D
20.
The electrons flow
from the Mg
electrode to the Cu
electrode; From
anode to cathode.
9.
Fe 3+ + 3e – ® Fe
10.
–More active than
carbon: aluminum,
Mg, or Na
–Less active than
carbon: zinc, Pb, Fe,
copper
11.
–source of electrical
energy –battery
12.
—Silver atoms
lose electrons and
become silver ions
in the solution.
—Some of the
Ag atoms become
Ag+ ions. —
Silver atoms are
oxidized to silver
ions.
13.
—The cell
requires electrical
energy for the
non-spontaneous
reaction to occur.
—The power
source causes some
Ag(s) atoms to
oxidize.
14.
Ni(s) key / nickel
15.
Ag+ + e - ® Ag or
2Ag+ + 2e - ® 2Ag
16.
2.0 mol.
17.
–Ni(s) or –the
nickle electrode