1. Which change in oxidation number represents oxidation?
A)
B)
C)
D)
E)
Sn2+(aq) ® Sn4+(aq)
Sn2+(aq) ® Sn(s)
Sn4+(aq) ® Sn2+(aq)
Sn4+(aq) ® Sn(s)
Sn(s) ® Sn2–(aq)
A)
B)
C)
D)
E)
2. In the reaction
A)
B)
C)
D)
E)
the oxidizing agent is:
A) Sn2+
B) Ag+
C) Sn4+
D) Ag
E) an unknown catalyst
3. In the half–reaction Na+ + e – ® Na, the sodium ion
gains electrons and is reduced.
gains electrons and is oxidized.
gains electrons but is neither oxidized nor reduced.
loses electrons and is oxidized.
loses electrons and is reduced.
4. Which equation correctly represents reduction?
A) Pb2+ ® Pb + 2e –
C) 2 Br – ® Br 2 + 2e –
E) All of these
increase the cell voltage
maintain electrical neutrality
increase the oxidation–reduction rate
supply a travel pathway for electrons
increase the rate of attainment of equilibrium
10. In the half–cell reaction Ca ®Ca2+ + 2e –, which is true
of the calcium atom?
Sn2+(aq) + 2 Ag + (aq) ® Sn4+(aq) + 2 Ag(s),
A)
B)
C)
D)
E)
9. The function of the salt bridge in an electrochemical cell
is to
It gains protons
It loses protons
It gains electrons
It loses electrons
It loses an electron and gains a proton
11. Consider the reaction,
S6+ + ? e –
S2–
How many electrons are needed to reduce S 6+ to S 2–?
A) 6
B) 2
C) 8
D) 4
E) 10
12. Which is the most easily reduced?
B) Pb2+ + 2e – ® Pb
D) 2 Br – + 2e – ® Br 2
5. The oxidation number of phosphorus in Na 4P2O7 is
A) –10
B) –5
C) +3
D) +10
E) +5
6. The oxidation number of carbon in CaC2O4 is
A) +7
B) +2
C) +3
D) +4
E) +6
7. What is the oxidation number of arsenic, As, in diarsenic
pentoxide, As2O5?
A) +10
B) +2
8. C2O42– + MnO2
C) +3
D) +4
E) +5
Mn 2+ + 2 CO 2
As a result of the above reaction, the oxidation number
of each C atom is
A) decreased by 1
C) decreased by 2
E) increased by 1
B) increased by 2
D) decreased by 4
A) Cl 2
B) Br 2
C) Hg2+ D) I 2
E) I –
13. Which half-reaction would occur at the cathode of an
electrochemical cell?
A)
B)
C)
D)
E)
Au ® Au3+ + 3e –
Au + 3e– ® Au3+
Au3+ ® Au + 3e–
Au 3+ + 3e – ® Au
Au + Au 3+ ® 3e – + Au3+
14. Which substance is the electrode that gains weight
during the operation of this electrochemical cell?
Cr/Cr 3+ || Pb 2+/Pb
17. For the following question refer to the table below.
What is the E° for this reaction?
A) Cr
C) Pb
E) both Cr and Pb
Cr 3+
B)
D) Pb2+
15. What is the oxidation potential for the reaction?
Cu
Cu2+ + 2e –
A) -0.52 V
C) +0.18 V
E) +0.52 V
2 Cr
A) +1.48 V
C) 0.00 V
E) –1.48 V
B) +0.74 V
D) –0.74 V
18. In an electrochemical cell, the positive ions go from the
B) -0.34 V
D) +0.34 V
A)
B)
C)
D)
E)
Zn/Zn2+||Pb 2+/Pb?
A)
B)
C)
D)
E)
B) 0.00 V
D) +0.96 V
anode to the cathode through the wire
cathode to the anode through the wire
anode to the cathode through the salt bridge
cathode to the anode through the salt bridge
cathode to the anode through the wire and anode to
the cathode through the salt bridge
19. To which electrode do the electrons move in the cell
16. What is the electrode potential of the standard hydrogen
half-cell reaction?
A) -0.83 V
C) +0.83 V
E) +1.23 V
2 Cr 3+ + 6e –
Pb
Pb2+
Zn
Zn2+
It cannot be determined unless the potentials are
known.
20. Base your answer on the table below.
22. Base your answer on the table below.
Which statement is true?
According to these data, which reaction takes place?
A) Br 2 will oxidize the chloride ion, but not the
iodide ion.
B) Br2 will oxidize the iodide ion, but not the
chloride ion.
C) I 2 will oxidize the chloride ion, but not the
bromide ion.
D) I 2 will oxidize the chloride ion, but not the
bromide ion.
E) Cl 2 will oxidize the bromide ion, but not the iodide
ion.
A)
B)
C)
D)
E)
2 Fe3+ + 3 Cd
2 Fe + 3 Cd 2+
2 Fe + 3 Cd2+
2 Fe 3++ 3 Cd
2 Fe+ 3 Cd
2 Fe 3+ + 3 Cd2+
2 Fe 3+ + 3 Cd2+
2 Fe + 3 Cd
3+
2+
2 Fe + 3 Cd
Fe 2Cd3 + 12e –
23. Base your answer on the table below.
21. Base your answer on the table below.
Which statement is true?
A)
B)
C)
D)
E)
Which substance will oxidize Fe2+ to Fe 3+?
A)
B)
C)
D)
E)
Al 3+ will oxidize Cr but not Ca.
Al 3+ will oxidize Ca but not Cr.
Ca2+ will oxidize Cr but not Al.
Ca2+ will oxidize Al but not Cr.
Cr 3+ will oxidize Al but not Ca.
24. Base your answer on the table below.
Ag
Al 3+
Li
Pb2+
MnO 4– (acid permanganate)
When Cu is placed in an aqueous solution of Ag(NO 3)
A)
B)
C)
D)
E)
Ag is produced.
no reaction occurs.
H2 gas is produced.
NO gas is produced.
Cu is reduced.
25. Consider this cell:
27. STANDARD ELECTRODE POTENTIALS
Ion Concentrations 1.0 M H2O at 298 K, 1 atm
Which is true?
What is the maximum voltage developed by this cell
when the switch is closed?
A) + 2.36 V
C) + 0.84 V
E) –0.04 V
A) Zinc metal reduces Sn 4+ to Sn 2+
B) Zinc metal reacts with HNO 3 to liberate hydrogen
gas
C) Zinc metal reacts with HNO3 to liberate NO
rather than H 2
D) Sn is oxidized to Sn 2+ when it reacts with HNO3
E) Sn2+ ions react with HNO3 to liberate NO rather
than H 2
28. Base your answer on the table below.
B) + 1.56 V
D) + 0.04 V
26. Base your answer on the table below.
Which species will reduce Cu 2+ to Cu?
Water can
A)
B)
C)
D)
E)
oxidize nickel, Ni.
oxidize copper, Cu.
oxidize fluorine gas, F2.
reduce magnesium ion, Mg 2+.
reduce fluorine gas, F 2.
A) Ag
C) Cl –
E) Sn2+
B) Au
D) H+ + MnO4–
29. Base your answer on the table below.
33. Which is the oxidized substance?
Mg(s) + 2 HCl(aq) ® MgCl 2(aq) + H 2(g)
What is the net potential developed by an
electrochemical cell with these half reactions?
A) +0.89 V
C) +0.63 V
E) –0.89 V
B) +0.76 V
D) –0.63 V
decreases to zero
decreases somewhat
increases somewhat
increases a large amount
remains the same
31. What is the net potential (E°) for this reaction at
equilibrium?
2 Fe 3+ + 2 I –
H2(g)
HCl(aq)
Mg(s)
MgCl 2(aq)
This is not a redox reaction
34. Which substance is reduced?
Pb(NO 3) 2 ® PbO 2 + 2 NO 2
30. As the reaction in an electrochemical cell approaches
equilibrium, the rate of the anode reaction
A)
B)
C)
D)
E)
A)
B)
C)
D)
E)
2 Fe 2+ + I 2
A) 0.00 volts
C) 1.00 volts
E) 2.08 volts
B) 0.23 volts
D) 1.31 volts
A)
B)
C)
D)
E)
35. Which ion can act as both an oxidizing agent and a
reducing agent in 1.0 M aqueous solution?
A) Al 3+
B) between 0 and –1
D) between 0 and 1
B) Cl –
C) Fe 3+
D) Sn2+
E) H+
36. Which substance is reduced?
5 HSO 3– + 2 IO3– ® 5 SO 42– + I 2 + 3 H+ + H2O
A)
B)
C)
D)
E)
I2
IO3–
SO 42–
HSO 3–
This is not a redox reaction
37. Consider the unbalanced redox equation skeleton.
Pb + Cr2O72– + H+ ® Pb2+ + Cr 3+ + H2O
32. In order for a redox reaction to be at equilibrium, the
potential (E°) must be
A) less than –1
C) 0
E) greater than 1
NO 2
PbO 2
Pb(NO 3) 2
O2–
This is not a redox reaction
Which is the balanced overall reaction?
A)
B)
C)
D)
Pb + Cr2O72– + H+ ® Pb2+ + Cr 3+ + H2O
Pb + Cr2O72– + 14 H+ ® Pb2+ + 2Cr 3+ + 7 H2O
Pb + Cr2O72– + H+ + 6e – ® Pb2+ + Cr 3+ + H2O
2 Pb + Cr2O72– + 14 H+ ® 2 Pb2+ + 2 Cr 3+ + 7 H2
O
E) 3 Pb + Cr 2O 72– + 14 H+ ® 3 Pb2+ + 2 Cr3+ + 7
H 2O
38. Which is correctly balanced?
A)
B)
C)
D)
E)
Ag + 2 HNO 3 ® AgNO3 + NO + H2O
Ag + 4 HNO 3 ® AgNO3 + 7 NO + 2H2O
3 Ag + 4 HNO 3 ® 3 AgNO3 + NO + 2 H2O
Ag + 2 HNO 3 ® AgNO3 + NO + 2 H2O
3 Ag + 4 HNO 3 ® 3 AgNO3 + NO + 2 H2O + 3e–
39. Which substance is oxidized?
2 NaOH + H 2SO 4 ®Na2SO 4 + 2 H2O
A)
B)
C)
D)
E)
H2O
NaOH
H2SO 4
Na2SO 4
This is not a redox reaction
40. Which substance is reduced?
2 NaOH + H 2SO 4 ®Na2SO 4 + 2 H2O
A)
B)
C)
D)
E)
H2O
NaOH
H2SO 4
Na2SO 4
This is not a redox reaction
43. A 1.0 M solution of ZnCl 2 is electrolyzed. Which are
the correct half–reactions?
A) Anode: 2 Cl –
Cl 2 + 2e –
2+
Cathode: Zn + 2e – Zn
B) Anode: 2 Cl –
Cl 2 + 2e –
Cathode: 2 H 2O + 2e–
H2 + 2 OH –
C) Anode: 2 H 2O
O 2 + 4 H+ + 4e –
2+
Cathode: 2 Zn + 4e –
2 Zn
D) Anode: 2 H2O
O2 + 4 H+ + 4e –
Cathode: 4 H 2O + 4e–
2 H2 + 4 OH –
E) Anode: Cl 2 + 2e –
2 Cl –
2+
Cathode: Zn
Zn + 2e –
44. A 1.0 M solution of NiBr2 is electrolyzed. Which are
the correct half–reactions?
41. Which is a redox reaction?
A)
B)
C)
D)
E)
BaSO 4 ® Ba2+ + SO 42–
Cu(NO 3) 2 + H2S ® CuS + 2 HNO 3
CaCO 3 ® CaO + CO 2
2 Al + 6 H2O ® 2 Al(OH) 3 + 3 H2
NH 4+ ® H+ + NH 3
42. What are the anode and cathode reactions during the
electrolysis of fused KBr?
–
A) Anode:
2 H2O ® O2 + 4 H+ + 4e Cathode: 4
K+ + 4e – ® 4 K
B) Anode: 2 Br – ® Br 2 + 2e – Cathode: 2 H 2O +
2e – ® H2 + 2 OH –
C) Anode: Br 2 + 2e – ® 2 Br – Cathode: 2 K ® 2
K+ + 2e –
D) Anode: 2 H2O ® O2 + 4 H+ + 4e – Cathode: 4 H
2 O + 4e – ® 2 H 2 + 4 OH –
E) Anode: 2 Br – ® Br2 + 2e – Cathode: 2 K + + 2e
–® 2K
A) Anode: Br 2+ 2e –
2 Br –
Cathode: Ni Ni 2+ + 2e –
B) Anode: 2 Br –
Br 2 + 2e –
Cathode: 2 H 2O + 2e–
H2 + 2 OH –
C) Anode: 2 H2O
O2 + 4 H+ + 4e –
Cathode: 2 Ni2+ + 4e –
2 Ni
D) Anode: 2 H2O
O2 + 4 H+ + 4e –
Cathode: 4 H 2O + 4e–
2 H2 + 4 OH –
E) Anode: 2 Br –
Br2 + 2e –
Cathode: Ni 2+ + 2e –
Ni
45. In the electrolysis of molten CaCl 2 , the species
oxidized is
A)
B)
C)
D)
E)
Ca
Ca2+
Cl –
Cl 2
Oxidation does not occur
46. What is the charge and the reaction occurring at the
anode of an electrolysis reaction?
A)
B)
C)
D)
E)
(+), oxidation
(+), reduction
(–), reduction
(–), oxidation
reactions only occur at the cathode
47. In the electrolysis of aqueous copper (II) bromide
solution, CuBr 2(aq), 1.00 gram of Cu is deposited at the
cathode. How many grams of bromine are formed at the
anode?
A) 2.00 grams
C) 3.00 grams
E) 159 grams
B) 2.52 grams
D) 79.9 grams
48. At the cathode during electrolysis, what is its charge
and what type of reaction occurs.
A)
B)
C)
D)
E)
(–), oxidation
(+), oxidation
(–), reduction
(+), reduction
no reaction occurs at the cathode
49. Electroplating occurs during electrolysis
A) at the wire
C) at the cathode
E) in solution
B) at the anode
D) at the salt bridge
50. If fused silver chloride, AgCl, is electrolyzed, the Ag+
ions are
A)
B)
C)
D)
E)
reduced at the negative electrode
reduced at the positive electrode
oxidized at the negative electrode
oxidized at the positive electrode
neither oxidized nor reduced
51. I. Potassium is a good oxidizing agent
BECAUSE
II. potassium is a metal and loses electrons easily.
A)
B)
C)
D)
I is TRUE, II is FALSE
I is FALSE, II is TRUE
I and II are BOTH FALSE
I and II are BOTH TRUE but II IS NOT a correct
explanation of I
E) I and II are BOTH TRUE and II IS a correct
explanation of I
52. I. Fluorine is a good oxidizing agent
BECAUSE
II. fluorine has a small atomic radius and gains an
electron easily.
A)
B)
C)
D)
I is TRUE, II is FALSE
I is FALSE, II is TRUE
I and II are BOTH FALSE
I and II are BOTH TRUE but II IS NOT a correct
explanation of I
E) I and II are BOTH TRUE and II IS a correct
explanation of I
53. I. Fluorine acts as an oxidizing agent when it combines
with sodium
BECAUSE
II. fluorine gains electrons in the reaction.
A)
B)
C)
D)
I is TRUE, II is FALSE
I is FALSE, II is TRUE
I and II are BOTH FALSE
I and II are BOTH TRUE but II IS NOT a correct
explanation of I
E) I and II are BOTH TRUE and II IS a correct
explanation of I
54. I. The oxidation number of Cu in CuSO 4 is +2
56. I. Iodine is a better oxidizing agent than fluorine
BECAUSE
BECAUSE
II. the oxidation state of sulfur is +4.
II. Iodine has a greater electronegativity value.
A)
B)
C)
D)
A)
B)
C)
D)
I is TRUE, II is FALSE
I is FALSE, II is TRUE
I and II are BOTH FALSE
I and II are BOTH TRUE but II IS NOT a correct
explanation of I
E) I and II are BOTH TRUE and II IS a correct
explanation of I
55. I. The oxidation number of Pb in PbSO 4 is +4
I is TRUE, II is FALSE
I is FALSE, II is TRUE
I and II are BOTH FALSE
I and II are BOTH TRUE but II IS NOT a correct
explanation of I
E) I and II are BOTH TRUE and II IS a correct
explanation of I
57. I. Fluorine is the best reducing agent
BECAUSE
BECAUSE
II. the oxidation state of sulfur is also +4.
II. when a species is reduced, it gains electrons.
A)
B)
C)
D)
A)
B)
C)
D)
I is TRUE, II is FALSE
I is FALSE, II is TRUE
I and II are BOTH FALSE
I and II are BOTH TRUE but II IS NOT a correct
explanation of I
E) I and II are BOTH TRUE and II IS a correct
explanation of I
I is TRUE, II is FALSE
I is FALSE, II is TRUE
I and II are BOTH FALSE
I and II are BOTH TRUE but II IS NOT a correct
explanation of I
E) I and II are BOTH TRUE and II IS a correct
explanation of I
Answer Key
Redox Practice 2
1.
A
37.
E
2.
B
38.
C
3.
A
39.
E
4.
B
40.
E
5.
E
41.
D
6.
C
42.
E
7.
E
43.
C
8.
E
44.
E
9.
B
45.
C
10.
D
46.
A
11.
C
47.
B
12.
A
48.
C
13.
D
49.
C
14.
C
50.
A
15.
B
51.
B
16.
B
52.
E
17.
B
53.
E
18.
C
54.
A
19.
A
55.
C
20.
B
56.
C
21.
E
57.
B
22.
A
23.
B
24.
A
25.
B
26.
E
27.
C
28.
E
29.
C
30.
B
31.
A
32.
C
33.
C
34.
C
35.
D
36.
B