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Chapter 17: Electrochemistry
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Self Quiz 2
Self Quiz 2
This activity contains 20 questions.
A half-reaction that takes place at an anode is represented by
Fe
2+
(
aq
) + 2e
-
---> Fe(
s
)
Ag(
s
) + Cl
-
(
aq
) ---> AgCl(
s
) + e
-
Cl
2
(
g
) + 2e
-
---> 2Cl
-
(
aq
)
Ag
+
(
aq
) + e
-
---> Ag(
s
)
2IO
3
-
(
aq
) + 12H
+
(
aq
) + 10e
-
---> I
2
(
s
) + 6H
2
O(
l
)
Which is
not
a characteristic of an anode?
Electrons in the wire move toward the anode.
Anions migrate toward the anode.
The electrons are produced at the anode.
The anode has a negative side.
The oxidation half-reaction occurs at the anode.
The redox reaction that matches the shorthand notation
Cr(
s
) | Cr
3+
(
aq
) || Br
2
(
l
) | Br
-
(
aq
) | Pt(
s
) for a galvanic cell is
Cr(
s
) + Cr
3+
(
aq
) ---> Br
2
(
l
) + 2Br
-
(
aq
)
2Cr(
s
) + 3Br
2
(
l
) ---> 2Cr
3+
(
aq
) + 6Br
-
(
aq
) + Pt(
s
)
2Cr(
s
) + 3Br
2
(
l
) ---> 2Cr
3+
(
aq
) + 6Br
-
(
aq
)
Cr(
s
) + Br
2
(
l
) ---> Cr
3+
(
aq
) + 2Br
-
(
aq
)
Cr(
s
) + 3/2Br
2
(
l
) ---> Cr
3+
(
aq
) + 3Br
-
(
aq
)
The balanced redox reaction that matches the shorthand notation
C(
s
) | I
-
(
s
) | I
2
(
s
) || O
2
(
g
) | H
2
O(
l
) | C(
s
) for a galvanic cell is
C(
s
) + 4I
-
+ O
2
(
g
) + 4H
+
(
aq
) ---> 2H
2
O>(
l
) + 2I
2
(
s
) + C(
s
)
4I
-
+ O
2
(
g
) + 4H
+
(
aq
) ---> 2H
2
O(
l
) + 2I
2
(
s
)
2I
-
+ O
2
(
g
) + 4H
+
(
aq
) ---> 2H
2
O(
l
) + I
2
(
s
)
4I
-
+ 2I
2
(
s
) ---> O
2
(
g
) + 2H
2
O(
l
) + 4H
+
(
aq
)
4I
-
+ O
2
(
g
) + 4H
+
(
aq
) + 4e
-
---> 2H
2
O(
l
) + 2I
2
(
s
) + 4e
-
The standard free-energy change (in kilojoules) at 25 °C for the reaction
O
2
(
g
) + 4H
+
(
aq
) + 4Cl
-
(
aq
) ---> 2H
2
O(
l
) + 2Cl
2
(
g
) , which has a standard cell potential = -0.13 V is
-25.1 kJ
25.1 kJ
5.02 x 10
4
kJ
50.2 kJ
-12.5 kJ
The standard cell potential at 25 °C for the reaction
Au
3+
(
aq
) + 3Ag(
s
) ---> Au(
s
) + 3Ag
+
(
aq
), which has a standard free-energy change = -203 kJ is
7.01 x 10
-4
V
0.701 V
-2.10 V
2.10 V
-0.701 V
Which statement concerning the arrangement of half-reactions in a table of half-cell potentials is true?
The weaker reducing agents are located in the bottom left of the table.
The weaker oxidizing agents are located in the bottom right of the table.
The stronger oxidizing agents are located in the bottom left of the table.
The weaker reducing agents are located in the top right of the table.
The stronger oxidizing agents are located in the bottom right of the table.
If the standard potential for the galvanic cell Pt(
s
) | Fe
2+
(
aq
) , Fe
3+
(
aq
) || Ce
4+
(
aq
) , Ce
3+
(
aq
) | Pt(
s
) is 0.84 V, then the standard reduction potential for the Ce
4+
(
aq
) /Ce
3+
half-cell is (E° for Fe
2+
/Fe
3+
half-cell = -0.77 V.)
0.07 V
-1.1 V
-1.61 V
1.61 V
-0.07 V
The reaction that
cannot
be reduced by Fe is (E° for Fe
2+
/Fe = -0.45 V)
Cl
2
, E° for Cl
2
/Cl
-
= 1.36 V
Mg
2+
, E° for Mg
2+
/Mg = -2.37 V
Pb
2+
, E° for Pb
2+
/Ag = -0.13 V
Ni
2+
, E° for Ni
2+
/Ni = -0.26 V
Sn
4+
, E° for Sn
4+
/Sn
2+
= 0.15 V
The reaction that is
not
spontaneous under standard state conditions is
Br
2
, E°
reduction
= 1.09 V for a Br
2
/Br
-
half-cell
Hg
2
2+
, E°
reduction
= 0.80 V for a Hg
2
2+
/Hg half-cell
Pb
2+
, E°
reduction
= -0.13 V for a Pb
2+
, Pb half-cell
I
2
, E°
reduction
= 0.54 V for an I
2
/I
-
half-cell
Br
2
(
l
) + Pb(
s
) ---> 2Br
-
(
aq
) + Pb
2+
(
aq
)
Hg
2
2+
(
aq
) + Pb(
s
) ---> 2Hg(
l
) + Pb
2+
(
aq
)
I
2
(
s
) + 2Br
-
(
aq
) ---> Br
2
(
l
) + 2I
-
(
aq
)
Hg
2
2+
(
aq
) + 2I
-
(
aq
) ---> 2Hg(
l
) + I
2
(
s
)
Br
2
(
l
) + 2Hg(
l
) ---> 2Br
-
+ Hg
2
2+
(
aq
)
The potential of a galvanic cell that uses the reaction
H
2
(
g
) + 2OH
-
(
aq
) + Sn
2+
(
aq
) ---> Sn(
s
) + 2H
2
O(
l
) at 25 °C when [OH
-
] = 0.010 M, [Sn
2+
] = 0.020 M, and P
H
2
= 1.0 atm is (E° = 0.97 V)
0.86 V
0.75 V
0.80 V
0.63 V
1.14 V
The [Ag
+
] in a galvanic cell that uses the reaction
2Ag
+
(
aq
) + Ni(
s
) ---> Ni
2+
(
aq
) + 2Ag(
s
) at 25 °C when [Ni
2+
] = 1.0 x 10
-4
M and E (measured) = 1.17 V is (E° = 1.06 V for this reaction)
0.52 M
1.4 x 10
-4
M
0.72 M
0.085 M
The pH in the anode half-cell of the galvanic cell Pt(
s
) | H
2
(
g
) (1 atm) | H
+
(? M) || Fe
2+
(1 M) | Fe at 25 °C, when E
measured
= 0.57 V is (E° for Fe
2+
/Fe = 0.45 V)
8.61
1.01
17.23
4.05
2.03
The equilibrium constant for the reaction Cr
2
O
7
2-
(
aq
) + 14H
+
(
aq
) + 6Br
-
(
aq
) ---> 2Cr
3+
(
aq
) + 3Br
2
(
l
) + 7H
2
O(
l
) at 25 °C is
(E° = 1.33 V for a Cr
2
O
7
2-
/Cr
3+
half-cell
E° = 1.09 V for a Br
2
/Br
-
half-cell)
2.1 x 10
24
1.4
1.5 x 10
12
4.7 x 10
-25
1.1 x 10
4
Which is a characteristic of an alkaline dry cell?
The oxidation products are different in the alkaline and acidic dry cells.
The anode and cathode reactions are switched relative to a dry cell under acidic conditions.
The use of alkaline conditions slows the corrosion of the zinc anode.
Zinc chloride is the product of the anode half-reaction.
The alkaline cell produces a lower power compared to the acidic dry cell.
Which is a characteristic of the corrosion of iron?
Rust is deposited in small pits that form during the corrosion process.
The rusting of iron requires only the presence of oxygen.
The rust is physically separated from small pits that form during the corrosion process.
The surface of the iron remains smooth during the corrosion process.
The rusting of iron requires only the presence of water.
Which explains aluminum's resistance to corrosion?
The aluminum oxide that forms adheres to the metal surface.
The water in the atmosphere reacts with the aluminum to form a protective coating of aluminum hydroxide.
The reduction half-reaction Al
3+
(
aq
) + 3e
-
---> Al(
s
) occurs readily.
Any aluminum oxide that forms readily falls off the metal and exposes the corrosion-resistant metal.
The standard reduction potential for the Al
3+
/Al half-reaction is above the standard reduction potential for the O
2
/H
2
O half-reaction.
Which conditions are correctly matched with the cell type?
spontaneous, positive voltage, positive free-energy change : galvanic cell
nonspontaneous, positive voltage, positive free-energy change : electrolytic cell
nonspontaneous, negative voltage, negative free-energy change : electrolytic cell
spontaneous, negative voltage, positive free-energy change : electrolytic cell
spontaneous, positive voltage, negative free-energy change : galvanic cell
Which is
not
a characteristic of the process used to manufacture aluminum?
The aluminum industry is the single largest consumer of electricity in the United States.
Oxygen gas is the product of the oxidation half-reaction.
The electrolyte is a mixture of Al
2
O
3
and Na
3
AlF
6
.
The molten aluminum is drawn off from the bottom of the electrolytic cell.
The graphite electrodes may be used indefinitely in the electrolytic cell.
How many grams of Cd(OH)
2
are reduced to Cd in a ni-cad battery when the battery is recharged with a 0.100 A current for 4.00 hours?
0.0182 g are reduced.
0.839 g are reduced.
1.09 g are reduced.
2.18 g are reduced.
4.37 g are reduced.
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