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Unit One - Redox and Electrochemistry
Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
F = 96500 C/mol
____
1. In which of the following compounds does nitrogen have the highest oxidation number?
a.
d.
b.
e.
c.
____
2. Which of the following equations does not represent an oxidation-reduction reaction?
a.
+
+
____
____
____
b.
+
c.
+
d.
+
e.
+
+
+
3. Experiments were performed with four strips of metals A, B, C, and D, and their corresponding nitrate
solutions
,
,
, and
. Metal
was placed in each of the solutions and
reactions were observed only in solutions containing
and
ions. Metal B did not react in any of the
solutions. Metal C reacted in the solution containing
ions, but was not tested in the other solutions. A list
of the metals in order of decreasing strength as reducing agents (strongest reducing agent is listed first) is
a. B A D C
d. D A C B
b. C B D A
e. B C A D
c. C D A B
4. Consider the following oxidation-reduction reaction:
Which of the following statements about this oxidation-reduction process is true?
a. iodine is oxidized and potassium is reduced
b. iodine is reduced and potassium is oxidized
c. potassium is oxidized and chlorine is reduced
d. chlorine is oxidized and hydrogen is reduced
e. iodine is both oxidized and reduced
5. Which of the following half-reaction equations are balanced?
I.
II.
III.
IV.
V.
____
a. I and II
d. III and V
b. II and IV
e. all are balanced
c. I and III
6. The following two half-reactions are involved in a galvanic cell:
____
At standard conditions, what species are produced at each electrode?
a.
is produced at the cathode and
at the anode
b.
is produced at the cathode and
at the anode
c.
is produced at the anode and
at the cathode
d.
is produced at the cathode and
at the anode
e.
is produced at the cathode and
at the anode
7. Given the standard reduction potentials for the following half-reactions:
What is
for the reaction
?
a. +0.05 V
b. +0.43 V
c. +1.11 V
d. +1.20 V
e. +1.88 V
Completion
Complete each sentence or statement.
8. The function of a salt bridge in a galvanic cell is to provide a pathway for the migration of
______________________________ between the two half-cells.
9. When an atom gains an electron, it is acting as a(n) ____________________ agent.
10. While an electrochemical cell is operating, the anions move internally toward the ____________________.
11. A galvanic cell consisting of mercury and lead in like 1.0 M nitrate solutions would have which metal as the
anode?
Short Answer - Knowledge (5 marks)
12. Will a reaction take place if a strip of zinc metal is placed in a solution of lead (II) sulfate? Justify your
answer. (2 marks)
13. Calculate
for the following equation: (2 marks)
Decide whether the equation represents a spontaneous or a nonspontaneous reaction at standard conditions.
14. What is the direction of the electron flow in the external circuit of an electrochemical cell while the cell is
operating? (1 mark)
Problem - Inquiry (14 marks)
15. Balance the following equation by the half-reaction method and fill in the oxidation and reduction half
reactions on the appropriate line. (4 marks)
MnO41- + I2 + H1+ --> MnO2 + IO31Essay
16. Balance the following redox reaction by the oxidation number method. Clearly label the oxidation and
reduction steps. (3 marks)
17. What are the problems associated with using the hydrogen fuel cell in electric cars? (3 marks)
Unit One - Redox and Electrochemistry
Answer Section
MULTIPLE CHOICE
1. ANS:
STA:
2. ANS:
STA:
3. ANS:
STA:
4. ANS:
STA:
5. ANS:
STA:
6. ANS:
STA:
7. ANS:
STA:
D
EL1.01
C
EL1.01
C
EL2.02
E
EL1.01
D
EL2.03
B
EL1.02
B
EL1.03
PTS: 1
REF: K/U
OBJ: 9.1
PTS: 1
REF: K/U
OBJ: 9.1
PTS: 1
REF: C
OBJ: 9.3
PTS: 1
REF: K/U
OBJ: 9.1
PTS: 1
REF: C
OBJ: 9.2
PTS: 1
REF: K/U
OBJ: 9.5
PTS: 1
REF: K/U
OBJ: 9.3
REF: K/U
OBJ: 9.5
STA: EL1.02
PTS: 1
10. ANS: anode
REF: K/U
OBJ: 9.3
STA: EL1.01
PTS: 1
11. ANS: lead
REF: C
OBJ: 10.1
STA: EL2.04
COMPLETION
8. ANS: migration of ions
PTS: 1
9. ANS: oxidizing
PTS: 1
SHORT ANSWER
12. ANS:
Oxidation half-reaction:
Reduction half-reaction:
Overall reaction:
for the overall reaction is positive. Thus a zinc strip will react spontaneously with lead (II) sulfate
solution.
PTS: 1
13. ANS:
REF: C
OBJ: 9.3
STA: EL2.05
Reduction half-reaction:
Oxidation half-reaction:
Overall reaction:
for the overall reaction is positive, thus the reaction is spontaneous as written.
PTS: 1
REF: C
OBJ: 9.3
STA: EL2.05
14. ANS:
The direction of the electron flow in an electrolytic cell is always from the anode to the cathode of the cell.
PTS: 1
REF: K/U
OBJ: 10.1
STA: EL1.02
PROBLEM
15. ANS:
a
PTS: 1
ESSAY
16. ANS:
+4 2 +1 +3 2 +1 +6 2 +2 +6 2 +4 2 +1 2
The change in the oxidation number of the oxidized element C = (+4) – (+3) = +1
The change in the oxidation number of the reduced element Mn = (+2) (+4) = –2
The lowest common multiple of 1 and 2 is 2. Thus in the balanced reaction two carbon atoms are needed for
every manganese atom. The increase and decrease in oxidation numbers will then be two for both. The
partially balanced equation is:
The remaining coefficients can be balanced by inspection and the balanced equation is:
PTS: 1
REF: C
OBJ: 9.2
STA: EL2.03
17. ANS:
- The high cost of the hydrogen fuel cell.
- the storage of hydrogen gas on board the vehicle presents safety concerns due to the flammable nature of
hydrogen.
- Where would the hydrogen gas (the cell fuel) come from? Electrolysis of water produces hydrogen at a
high cost.
- The distribution of hydrogen at retail outlets is associated with storage and handling hazards.
PTS: 1
REF: MC
OBJ: 9.4
STA: EL3.01