Chemistry, 6e (McMurry/Fay)
Chapter 17 Electrochemistry
17.1 Multiple-Choice Questions
1) Which of the following terms can be used to describe an electrochemical cell in which a spontaneous
chemical reaction generates an electric current?
I. an electrolytic cell
II. a galvanic cell
III. a voltaic cell
A) only I
B) only II
C) only III
D) II and III
2) Which cell involves a nonspontaneous redox reaction?
A) concentration cell
B) electrolytic cell
C) fuel cell
D) galvanic cell
3) During an electrochemical reaction, electrons move through the external circuit toward the ________
and positive ions in the cell move toward the ________.
A) anode, anode
B) anode, cathode
C) cathode, anode
D) cathode, cathode
4) For a galvanic cell, the cathode has a ________ sign and is the site of ________.
A) negative, oxidation
B) negative, reduction
C) positive, oxidation
D) positive, reduction
5) A salt bridge is used to
A) provide reactants in a fuel cell.
B) determine the direction of the cell reaction.
C) control whether the cell is electrolytic or galvanic.
D) allow the ion flow necessary for cell neutrality.
6) In a galvanic cell, the half-reaction MnO4–(aq) + 8 H+(aq) + 5 e– → Mn2+(aq) + 4 H2O(l) is
A) an oxidation half-reaction and occurs at the anode.
B) an oxidation half-reaction and occurs at the cathode.
C) a reduction half-reaction and occurs at the anode.
D) a reduction half-reaction and occurs at the cathode.
7) In a galvanic cell, the half-reaction H2(g) + 2 OH–(aq) → 2 H2O(l) + 2 e– is
A) an oxidation half-reaction and occurs at the anode.
B) an oxidation half-reaction and occurs at the cathode.
C) a reduction half-reaction and occurs at the anode.
D) a reduction half-reaction and occurs at the cathode.
8) What species is oxidized in the reaction: CuSO4(aq) + Fe(s) → FeSO4(aq) + Cu(s)?
A) CuSO4 (aq)
B) Fe (s)
C) FeSO4 (aq)
D) Cu (s)
9) Given that Cl2(g) + 2 e– → 2 Cl–(aq) is the reduction half-reaction for the overall reaction
2 Ag(s) + Cl2 (g) → 2 AgCl(s), what is the oxidation half reaction?
A) Ag(s) → Ag+(aq) + e–
B) Ag(s) + Cl–(aq) → AgCl(s) + e–
C) Ag(s) + Cl2(g) + e– → AgCl(s) + Cl–(aq)
D) 2 Cl–(aq) → Cl2(g) + 2 e–
10) What is the reduction half-reaction for the following overall cell reaction?
Ni2+(aq) + 2 Ag(s) → Ni(s) + 2 Ag+(aq)
A) Ag(s) + e– → Ag+(aq)
B) Ag+(aq) + e– → Ag(s)
C) Ni2+(aq) + 2 e– → Ni(s)
D) Ni2+(aq) + e– → Ni(s)
11) The iron content of foods can be determined by dissolving them in acid (forming Fe3+), reducing
the iron(III) to iron(II), and titrating with cerium(IV):
Fe2+(aq) + Ce4+(aq) → Fe3+(aq) + Ce3+(aq).
Identify the two half-reactions in the above reaction.
A) oxidation half-reaction reduction half-reaction
Fe2+(aq) + e–→ Fe3+(aq) Ce4+(aq) → Ce3+(aq) + e–
B) oxidation half-reaction reduction half-reaction
Fe2+(aq) → Fe3+(aq) + e– Ce4+(aq) + e– → Ce3+(aq)
C) oxidation half-reaction reduction half-reaction
Ce4+(aq) + e– → Ce3+(aq) Fe2+(aq) → Fe3+(aq) + e–
D) oxidation half-reaction reduction half-reaction
Ce4+(aq) → Ce3+(aq) + e– Fe2+(aq) + e– → Fe3+(aq)
12) For a galvanic cell that uses the following two half-reactions,
Cr2O72-(aq) + 14 H+(aq) + 6 e– → 2 Cr3+(aq) + 7 H2O(l)
Pb(s) → Pb2+(aq) + 2 e–
how many moles of Pb(s) are oxidized by one mole of Cr2O72-?
A) 1
B) 2
C) 3
D) 6
13) A galvanic cell employs the reaction
Mg2+(aq) + Cu(s) → Mg(s) + Cu2+(aq)
and NaNO3 is the salt used in the salt bridge. During the course of the reaction
A) Na+ leaves the salt bridge and enters the anode compartment.
B) NaNO3 leaves the salt bridge and enters the anode compartment.
C) Na+ leaves the salt bridge and enters the cathode compartment.
D) NaNO3 leaves the salt bridge and enters the cathode compartment.
14) What is the shorthand notation that represents the following galvanic cell reaction?
Fe(s) + Cu(NO3)2(aq) → Fe(NO3)2(aq) + Cu(s)
A) Fe(s) ∣ Fe2+(aq) ∣∣ Cu2+(aq) ∣ Cu(s)
B) Cu(s) ∣ Cu2+(aq) ∣∣ Fe2+(aq) ∣ Fe(s)
C) Fe(s) ∣ NO3–(aq) ∣∣ NO3–(aq) ∣ Cu(s)
D) Cu(s) ∣ Cu(NO3)2(aq) ∣∣ Fe(NO3)2(aq) ∣ Fe(s)
15) What is the shorthand notation that represents the following galvanic cell reaction?
2 Fe2+(aq) + Cl2(g) → 2 Fe3+(aq) + 2 Cl–(aq)
A) Fe2+(aq) ∣ Fe3+(aq) ∣∣ Cl2(g) ∣ Cl–(aq)
B) Fe(s) ∣ Fe2+(aq) ∣∣ Fe3+(aq) Cl2(g) ∣ Cl–(aq) ∣ C(s)
C) Pt(s) ∣ Fe3+(aq), Fe2+(aq), Cl2(g) ∣∣ Cl–(aq) ∣ C(s)
D) Pt(s) ∣ Fe2+(aq), Fe3+(aq) ∣∣ Cl2(g) ∣ Cl–(aq) ∣ C(s)
16) What is the shorthand notation for a galvanic cell that represents the following galvanic cell
reaction?
Br2(l) + 2 I–(aq) → 2 Br–(aq) + I2(s)
A) I–(aq)|I2(s) ∣∣Br2(l)|Br–(aq)
B) I–(aq)|I2(s) ∣∣Br2(l)|Br–(aq)|Pt(s)
C) Pt(s)|I–(aq)|I2(s) ∣∣Br2(l)|Br–(aq)
D) Pt(s)|I–(aq)|I2(s) ∣∣Br2(l)|Br–(aq)}Pt(s)
17) What is the balanced equation for the galvanic cell reaction expressed using shorthand notation
below?
Pt(s)|Sn2+(aq)|Sn4+(aq)∣∣Br2(l)|Br–(aq)|Pt(s)
A) Sn2+(aq) + Br2(l) → Sn4+(aq) + 2 Br–(aq)
B) Sn2+(aq) + 2 Br–(aq) → Sn4+(aq) + Br2(l)
C) Sn4+(aq) + Br2(l) → Sn2+(aq) + 2 Br–(aq)
D) Sn4+(aq) + 2 Br–(aq) → Sn2+(aq) + Br2(l)
18) The shorthand notation for the galvanic cell reaction Fe3+(aq) + 2 I–(aq) → Fe2+(aq) + I2(s)
requires an inert electrode on
A) both sides of the salt bridge
B) neither side of the salt bridge
C) only on the left side of the salt bridge
D) only on the right side of the salt bridge
19) In the shorthand notation for a galvanic cell, a double vertical line (∣∣) represents
A) a double phase boundary
B) an inert electrode
C) a phase boundary
D) a salt bridge
20) For the galvanic cell reaction, expressed below using shorthand notation, what half-reaction occurs
at the cathode?
Zn(s) ∣ Zn2+(aq) ∣∣ Ni2+(aq) ∣ Ni(s)
A) Zn(s) → Zn2+(aq) + 2 e–
B) Zn2+(aq) + 2 e– → Zn(s)
C) Ni(s) → Ni2+(aq) + 2 e–
D) Ni2+(aq) + 2 e– → Ni(s)
21) For the galvanic cell reaction, expressed below using shorthand notation, what half-reaction occurs
at the anode?
Mg(s) ∣ Mg2+(aq) ∣∣ Cd2+(aq) ∣Cd(s)
A) Mg(s) → Mg2+(aq) + 2 e–
B) Mg2+(aq) + 2 e– → Mg(s)
C) Cd(s) → Cd2+(aq) + 2 e–
D) Cd2+(aq) + 2 e– → Cd(s)
22) What is the balanced chemical equation for the galvanic cell reaction expressed using shorthand
notation below?
Al(s) ∣ Al3+(aq) ∣∣ Ni2+(aq) ∣ Ni(s)
A) 2 Al(s) + 3 Ni2+(aq) → 2 Al3+(aq) + 3 Ni(s)
B) 3 Al(s) + 2 Ni2+(aq) → 3 Al3+(aq) + 2 Ni(s)
C) 2 Ni(s) + 3 Al3+(aq) → 2 Ni2+(aq) + 3 Al(s)
D) 3 Ni(s) + 2 Al3+(aq) → 3 Ni2+(aq) + 2 Al(s)
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23) What is the balanced equation for the galvanic cell reaction expressed using shorthand notation
below?
Mg(s) ∣ Mg2+(aq) ∣∣ Cl2(g) ∣ Cl–(aq) ∣ C(s)
A) Mg(s) + 2 Cl–(aq) → Mg2+(aq) + Cl2(g)
B) Mg(s) + Cl2(g) → Mg2+(aq) + 2 Cl–(aq)
C) Mg2+(aq) + 2 Cl–(aq) → Mg(s) + Cl2(g)
D) Mg2+(aq) + 2 Cl–(aq) → MgCl2(s)
24) For the galvanic cell Pt(s) ∣ Sn2+(aq), Sn4+(aq) ∣∣ Pb2+(aq) ∣ Pb(s), what is the function of the
Pt(s)?
A) Pt is the anode and is a reactant in the overall cell reaction.
B) Pt is the anode and does not appear in the overall cell reaction.
C) Pt is the cathode and is a product in the overall cell reaction.
D) Pt is the cathode and does not appear in the overall cell reaction.
25) Write the overall cell reaction for the galvanic cell given below.
Pt(s) ∣ H2(g) ∣ H+(aq) ∣∣ Cl2(g) ∣ Cl–(aq) ∣ Pt(s)
A) Pt(s) + H2(g) + Cl–(aq) → Pt(s) + 2 H+(aq) + 2 Cl2(g)
B) 2 H+(aq) + 2 Cl2(g) → 2 HCl(aq)
C) H2(g) + Cl2(g) → 2 H+(aq) + 2 Cl–(aq)
D) No reaction would occur because there is no salt bridge.
26) What is the relation between joules (J), volts (V), and coulombs (C)?
A) 1 J = 1 V × 1 C
B) 1 J = 1 V ÷ 1 C
C) 1 J = 1 C ÷ 1 V
D) 1 J = 1 V × 1 C2
27) In the relationship ΔG = –nFE°, what is the value of n for the reaction shown below?
3 Cu2+(aq) + 2 Al(s) → 3 Cu(s) + 2 Al3+(aq)
A) 1
B) 2
C) 3
D) 6
28) The cell reaction for a dry cell battery is
Zn(s) + 2 MnO2(s) + 2 NH4+(aq) → 2 NH3(aq) + Mn2O3(s) + Zn2+(aq) + H2O(l).
The standard cell potential for this cell is 1.56 V. What is the standard free energy change for this cell?
A) +151 kJ
B) -151 kJ
C) -301 kJ
D) -602 kJ
29) For the reaction 2 Al(s) + 3 Co2+(aq) → 2 Al3+(aq) + 3 Co(s), ΔG° is -799 kJ. What is E° for a
standard cell based on this reaction?
A) +1.38 V
B) +2.76 V
C) +4.14 V
D) +8.28 V
30) The nickel-cadmium battery cell has a standard potential of +1.20 V. The cell reaction is
2 NiO(OH)(s) + Cd(s) + 2 H2O(l) → 2 Ni(OH)2(s) + Cd(OH)2(s).
What is the standard free energy change for this reaction?
A) -38.7 kJ
B) -116 kJ
C) -232 kJ
D) -463 kJ
31) Doubling all the coefficients in the equation for the cell reaction
A) doubles both E° and ΔG°.
B) doubles E°, but does not change ΔG°.
C) doubles ΔG°, but does not change E°.
D) does not change E° or ΔG°.
32) What is the relation between ΔG° and E° for the cell reaction below?
Ni2+(aq) + Cd(s) → Cd2+(aq) + Ni(s)
A) ΔG° = F E°
B) ΔG° = 2 F E°
C) ΔG° = –F E°
D) ΔG° = -2 F E°
33) For the hypothetical reaction A + Bx → Ax + B, E° = 1.19 V = and ΔG° = -115 kJ. For this reaction
the value of x = .
A) 1
B) 2
C) 3
D) 4
34) For the hypothetical reaction A + 2 Bx → Ay + 2 B, E° = 1.50 V = and ΔG° = -305 kJ. For this
reaction, if the value of x is 4, then the value of y = .
A) 1
B) 2
C) 3
D) 4
35) Which is not true for standard electrode potentials?
A) Cell constituents are in their standard states.
B) E° for oxidation is the negative of E° for reduction.
C) The half-reactions are written as reductions.
D) The potential for the standard hydrogen electrode is chosen to be +1.00 V.
36) What is the relationship between the standard cell potentials, E°, for the following two galvanic cell
reactions?
I. 3 Cu2+(aq) + 2 Al(s) → 3 Cu(s) + 2 Al3+(aq)
II. 6 Cu2+(aq) + 4 Al(s) → 6 Cu(s) + 4 Al3+(aq)
A) E°(I) = E°(II)
B) E°(I) =
1
2
E°(II)
C) E°(I) = 2E°(II)
D) E°(I) = E°(II)2
37) What is the relationship between the standard cell potentials, E°, for the following two galvanic cell
reactions?
I. 2 Ag+(aq) + Sn2+(aq) → Sn4+(aq) + 2 Ag(s)
II. Ag(s) + 1/2 Sn4+(aq) → 1/2 Sn2+(aq) + Ag+(aq)
A) E°(I) = E°(II)
B) E°(I) = 2E°(II)
C) E°(I) = – E°(II)
D) E°(I) = – 2E°(II)
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38) What is the standard cell potential for the reaction below?
Mg(s) + Br2(l) → Mg2+(aq) + 2 Br–(aq)
The standard reduction potential is -2.37 V for the Mg2+/Mg half-cell and +1.09 V for the Br2/Br– half-
cell.
A) -3.46 V
B) -1.28 V
C) +1.28 V
D) +3.46 V
39) The standard potential for the following galvanic cell is +0.90 V:
3 Cu2+(aq) + 2 Ga(s) ⇌ 3 Cu(s) + 2 Ga3+(aq)
Given that the standard reduction potential for the Cu2+/Cu half-cell is +0.34 V, what is the standard
reduction potential for the Ga3+/Ga half-cell?
A) -1.34 V
B) -0.56 V
C) +0.56 V
D) +1.36 V
Topic: Section 17.4 Standard Reduction Potentials
40) A galvanic cell consists of a La3+/La half-cell and a standard hydrogen electrode. If the La3+/La
half-cell standard cell functions as the anode, and the standard cell potential is 2.52 V, what is the
standard reduction potential for the La3+/La half-cell?
A) -2.52 V
B) -0.84 V
C) +0.84 V
D) +2.52 V
41) A galvanic cell consists of one half-cell that contains Ag(s) and Ag+(aq), and one half-cell that
contains Cu(s) and Cu2+(aq). What species are produced at the electrodes under standard conditions?
Ag+(aq) + e– → Ag(s) E° = +0.80 V
Cu2+(aq) + 2 e– → Cu(s) E° = +0.34 V
A) Ag(s) is formed at the cathode, and Cu(s) is formed at the anode.
B) Ag(s) is formed at the cathode, and Cu2+ (aq) is formed at the anode.
C) Cu(s) is formed at the cathode, and Ag+(aq) is formed at the anode.
D) Cu2+(aq) is formed at the cathode, and Cu(s) is formed at the anode.
42) Based on the half-reactions and their respective standard reduction potentials below, the strongest
reducing agent is ________, and the strongest oxidizing agent is ________.
Ag+(aq) + e– → Ag(s) 0.80 V
2 H+(aq) + 2 e– → H2(g) 0.00 V
Cd2+(aq) + 2 e– → Cd(s) -0.40 V
A) Ag, Cd2+
B) Ag+, Cd
C) Cd, Ag+
D) Cd2+, Ag
43) Consider the following standard reduction potentials,
Al3+(aq) + 3 e– → Al(s) E° = -1.66 V
I2(s) + 2 e– → 2 I–(aq) E° = +0.54 V
Under standard conditions,
A) Al3+(aq) is a stronger oxidizing agent than I2(s), and I–(aq) is a stronger reducing agent than Al(s).
B) I2(s) is a stronger oxidizing agent than Al3+(aq), and Al(s) is a stronger reducing agent than I–(aq).
C) Al(s) is a stronger oxidizing agent than I–(aq), and Al3+(aq) is a stronger reducing agent than I2(s).
D) I–(aq) is a stronger oxidizing agent than Al(s), and I2(s) is a stronger reducing agent than Al3+(aq).
44) Based on the following information,
F2(g) + 2 e– → 2 F–(aq) E° = +2.87 V
Mg2+(aq) + 2 e– → 2 Mg(s) E° = -2.37 V
which of the following chemical species is the strongest reducing agent?
A) F2(g)
B) Mg2+(aq)
C) F–(aq)
D) Mg(s)
45) Using the following standard reduction potentials
Fe3+(aq) + e– → Fe2+(aq) E° = +0.77 V
Pb2+(aq) + 2 e– → Pb(s) E° = -0.13 V
calculate the standard cell potential for the galvanic cell reaction given below, and determine whether or
not this reaction is spontaneous under standard conditions.
Pb2+(aq) + 2 Fe2+(aq) → 2 Fe3+(aq) + Pb(s)
A) E° = -0.90 V, nonspontaneous
B) E° = -0.90 V, spontaneous
C) E° = +0.90 V, nonspontaneous
D) E° = +0.90 V, spontaneous
46) Given: Ag+(aq) + e– → Ag(s) E° = +0.799 V
AgI(s) + e– → Ag(s) + I–(aq) E° = -0.152 V
Ni2+(aq) + 2 e– → Ni(s) E° = -0.267 V
Which of the following reactions should be spontaneous under standard conditions?
I. 2 AgI(s) + Ni(s) → 2 Ag(s) + 2 I–(aq) + Ni2+(aq)
II. Ag+(aq) + I–(aq) → AgI(s)
A) I and II are both nonspontaneous.
B) I is nonspontaneous and II is spontaneous.
C) I is spontaneous and II is nonspontaneous.
D) I and II are both spontaneous.
47) Based on the half-reactions and their respective standard reduction potentials below, what is the
standard cell potential for the reaction that is expected to occur?
Fe3+(aq) + e– → Fe2+(aq) 0.77 V
Sn4+(aq) + 2 e– → Sn2+(aq) 0.15 V
Pb2+(aq) + 2 e– → Pb(s) -0.13 V
A) 0.28 V
B) 0.64 V
C) 0.90 V
D) 1.03 V
48) Based on the half-reactions and their respective standard reduction potentials below, which addition
to an aqueous solution containing Fe(NO3)2 will result in a reaction under standard-state conditions?
O2(g) + 4 H+ +4 e– → 2 H2O(l) 1.23 V
Fe3+(aq) + e– → Fe2+(aq) 0.77 V
Cu2+(aq) + 2 e– → Cu(s) 0.34 V
2 H+(aq) + 2 e– → H2(g) 0.00 V
Ni2+(aq) + + 2 e– → Ni(s) -0.26 V
Fe2+(aq) + 2 e– → Fe(s) -0.45 V
A) aqueous copper(II) acetate
B) nickel wire
C) hydrogen gas
D) oxygen gas
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49) According to Table 17.1, which aqueous metal ion will reduce Ag+, but not Cu2+?
A) Fe2+
B) Fe3+
C) Mn2+
D) Sn2+
50) According to Table 17.1, which will reduce water but not Mg2+?
A) Al3+(aq)
B) Al(s)
C) Na+(aq)
D) Na(s)
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51) Using Table 17.1, find E° for 2 H2O(l) → 2 H2(g) + O2(g).
A) -2.06 V
B) -1.23 V
C) -0.80 V
D) -0.40 V
Topic: Section 17.5 Using Standard Reduction Potentials
52) Use Table 17.1 to calculate the standard potential for the reaction
O2(g) + 4 H+(aq) + 2 Cu(s) → 2 Cu2+(aq) + 2 H2O(l).
A) -1.57 V
B) -0.89 V
C) +0.89 V
D) +1.57 V
53) Use Table 17.1 to determine which of the following is the best oxidizing agent.
A) Fe3+
B) I2
C) MnO4–
D) Pb2+
54) Consider the following table of standard half-cell potentials:
A2 + 2 e– → 2 A– E° = + 1.09 V
B4+ + 2 e– → B2+ E° = + 0.15 V
C3+ + 3 e– → C E° = – 1.66 V
D2+ + 2 e– → D E° = – 2.37 V
Which substance is the strongest oxidizing agent?
A) A2
B) B4+
C) C3+
D) D2+
55) What is the Al3+:Ag+concentration ratio in the cell Al(s) | Al3+(aq) ∣∣ Ag+(aq) | Ag(s) if the
measured cell potential is 2.34 V?
A) 0.0094:1
B) 0.21:1
C) 4.7:1
D) 110:1
56) Consider the galvanic cell, Pb(s) | Pb2+(aq) || Cu2+(aq) | Cu(s). Which one of the following changes
to the cell would cause the cell potential to increase (i.e., become more positive)?
A) increase the [Pb2+] concentration
B) increase the [Cu2+] concentration
C) increase the mass of Pb(s)
D) decrease the mass of Pb(s)
57) Consider the galvanic cell, Pt(s) | H2(1 atm) | H+(1 M) || Cl–(1 M) | Hg2Cl2(s) | Hg(l). Which one of
the following changes to the cell would cause the cell potential to increase (i.e., become more positive)?
A) decrease the mass of Pt
B) increase the mass of Pt
C) decrease the pH
D) increase the pH
58) Calculate the value of the reaction quotient, Q, for the galvanic cell expressed using shorthand
notation below. Use the balanced chemical equation that has the smallest whole number stoichiometric
coefficients.
Zn(s) ∣ Zn2+(aq, 0.0100 M) ∣∣ Ag+(aq, 1.25 M) ∣ Ag(s)
A) 156
B) 125
C) 8.00 × 10-3
D) 6.40 × 10-3
59) Calculate the cell potential at 25°C for the cell
Fe(s) ∣ (Fe2+(0.100 M) ∣∣ Pd2+(1.0 × 10-5 M) ∣ Pd(s)
given that the standard reduction potential for Fe2+/Fe is -0.45 V and for Pd2+/Pd is +0.95 V.
A) +1.16 V
B) +1.28 V
C) +1.52 V
D) +1.68 V
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60) Calculate the cell potential E at 25°C for the reaction
2 Al(s) + 3 Fe2+(aq) → 2 Al3+(aq) + 3 Fe(s)
given that [Fe2+] = 0.020 M, [Al3+] = 0.10 M, and the standard reduction potential is -1.66 V for
Al3+/Al and -0.45 V for Fe2+/Fe.
A) +1.03 V
B) +1.17 V
C) +1.18 V
D) +1.20 V
61) At 25°C, E° = +1.88 V for a cell based on the reaction
3 AgCl(s) + Al(s) → 3 Ag(s) + Al3+(aq) + 3 Cl–(aq).
Find the cell potential E if [Al3+] = 0.20 M and [Cl–] = 0.010 M.
A) +2.01 V
B) +2.04 V
C) +2.28 V
D) cannot be calculated without the amounts of AgCl, Al, and Ag
62) Given that E° = +0.897 V, calculate E at 25°C for
Pb(s) ∣ Pb2+(0.0400 M) ∣∣ Fe3+(0.200 M), Fe2+(0.0100 M) ∣ Pt(s)
A) +0.779 V
B) +0.935 V
C) +1.015 V
D) +1.134 V
63) Given that E°red = -0.26 V for Ni2+/Ni at 25°C, find E° and E for the concentration cell expressed
using shorthand notation below.
Ni(s) ∣ Ni2+(aq, 1.0 × 10-5 M) ∣∣ Ni2+(aq, 0.100 M) ∣ Ni(s)
A) E° = 0.00 V and E = +0.24 V
B) E° = 0.00 V and E = +0.12 V
C) E° = -0.26 V and E = -0.02 V
D) E° = -0.26 V and E = -0.14 V
64) Given pH2 = 0.100 atm, [Cd2+] = 0.200 M, and [H+] = 1.00 × 10-5 M, calculate E at 25°C for a cell
based on the reaction:
Cd(s) + 2 H+(aq) → H2(g) + Cd2+(aq) Eo = +0.40 V.
A) -0.09 V
B) +0.12 V
C) +0.15 V
D) +0.30 V
65) If the cell reaction involves ions in solution, as the cell reaction in a galvanic cell continues,
A) E for the cell increases.
B) E for the cell decreases.
C) E° for the cell increases.
D) E° for the cell decreases.
66) How many moles of electrons, n, are transferred in the following reduction-oxidation reaction?
2 MnO4–(aq) + 16 H+(aq) + 10 Cl–(aq) → 2 Mn2+(aq) + 5 Cl2(g) + 8 H2O(l)
A) 2
B) 4
C) 5
D) 10
67) Consider the half-reaction: MnO4– (aq) + 8 H+ (aq) + 5 e– → Mn2+ (aq) + 4 H2O(l). The formation
of MnO4– from Mn2+ occurs most readily when the solution is
A) acidic.
B) neutral.
C) basic.
D) The reaction is not dependent upon pH.
68) Which is most often used in the laboratory to measure pH?
A) a standard hydrogen electrode
B) a glass electrode
C) a Daniell cell
D) a conductivity cell
69) The following cell has a potential of 0.45 V at 25°C.
Pt(s) ∣ H2(1 atm)|H+(? M) ∣∣ Cl–(1 M) ∣ Hg2Cl2(s)|Hg(l)
The standard half-cell potential for the half-reaction Hg2Cl2(s) + 2 e– → 2 Hg(l) + 2 Cl–(aq) is 0.28 V.
What is the pH in the anode compartment?
A) 2.9
B) 4.7
C) 7.6
D) 12.3
70) A cell based on the reaction below has a standard potential of +0.42 V at 25°C. If all of the species
are at standard conditions except [H+], at what pH will the cell have a potential of zero?
H2O2(aq) + 2 H+(aq) + 2 Cl–(aq) → Cl2(aq) + 2 H2O(l)
A) 3.55
B) 7.09
C) 10.6
D) 14.2
71) Consider a cell based on the following reaction:
GeO(s) + H2O(l) + 2 Ag+(aq) → GeO2(s) + 2 H+(aq) + 2 Ag(s)
If [Ag+] = 1 M, at 25°C,
A) pH = 2(E° – E)/0.0592 V.
B) pH = (E° – E)/0.0592 V.
C) pH = (E – E°)/0.0592 V.
D) pH = 2(E – E°)/0.0592 V.
72) Consider the following cell:
Pt(s) ∣ H2(g, p1) ∣ H+(aq, pHA) ∣∣ H+(aq, pHC) ∣ H2(g, p2) ∣ Pt(s)
Where pHA is the pH of the aqueous solution in the anode half-cell and pHC is the pH of the aqueous
solution in the cathode half-cell. If the partial pressure of H2(g) is the same for both half-cells, (p1 = p2),
then E for the cell at 25°C is
A) 0.0296 V log (pHA/pHC).
B) 0.0296 V log (pHC/pHA).
C) 0.0592 V (pHA – pHC).
D) 0.0592 V (pHC – pHA).
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73) When a cell reaction reaches equilibrium,
A) E° = 0.
B) E = 0.
C) both E° and E = 0.
D) neither E° nor E = 0.
74) The equilibrium constant, K, can be calculated from
A) E°.
B) E.
C) either E° or E.
D) neither E° nor E.
75) Calculate the equilibrium constant, K, at 25°C for the galvanic cell reaction shown below:
A) 3.2 × 10-63
B) 3.2 × 10-13
C) 3.2 × 1012
D) 3.2 × 1062
76) Ag+(aq) + e– → Ag(s) E° = +0.800 V
AgBr(s) + e– → Ag(s) + Br–(aq) E° = +0.071 V
Br2(l) + 2 e– → 2 Br–(aq) E° = +1.066 V
Use some of the data above to calculate Ksp at 25°C for AgBr.
A) 6.3 × 10-2
B) 4.9 × 10-13
C) 1.9 × 10-15
D) 2.4 × 10-34
77) For a particular cell based on the reaction:
3 AgCl(s) + Al(s) → 3 Ag(s) + Al3+(aq) + 3 Cl–(aq)
E = +1.750 V and E° = +1.884 V at 25°C.
What is the value of the equilibrium constant, K, at 25°C for the reaction?
A) 3.6 × 1029
B) 6.7 × 1031
C) 4.8 × 1088
D) 3.0 × 1095
78) A particular 12V battery is based on a reaction having a standard cell potential, E° = +1.92 V. What
happens when the battery “dies”?
A) E° = 0 V and E = 0 V
B) E° = 0 V and E = 12 V
C) E° = +1.92 V and E = 0 V
D) E° = +1.92 V and E = 12 V
79) For a particular battery based on one of the following reactions, E is expected to remain constant
with time until the cell reactants are almost completely consumed. Which is the appropriate reaction?
A) Zn(s) + 2 MnO2(s) + 2 NH4+(aq) → 2 NH3(aq) + Mn2O3(s) + Zn2+(aq) + H2O(l)
B) 2 NiO(OH)(s) + Cd(s) + 2 H2O(l) → 2 Ni(OH)2(s) + Cd(OH)2(s)
C) Pb(s) + PbO2(s) + 2 H+(aq) + 2 HSO4–(aq) → 2 PbSO4(s) + 2 H2O(l)
D) Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s)
80) The cell reaction for a lead storage battery is:
Pb(s) + PbO2(s) + 2 H+(aq) + 2 HSO4–(aq) → 2 PbSO4(s) + 2 H2O(l)
E° = +1.92 V
To provide a potential of about 12 V, one could
A) adjust the pH to 12.
B) adjust the pH to 1.
C) connect six cells in series.
D) greatly increase the surface area of the Pb(s) and PbO2(s).
81) Which battery does not use MnO2(s) as a cell reactant?
A) an alkaline dry cell.
B) a Leclanche’ dry cell.
C) a lithium battery.
D) a “ni-cad” battery.