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 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
59) 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
22
60) 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
61) 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
62) 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
63) Given and calculate E at 25°C for a cell based
on the reaction:
A) -0.09 V
B) +0.12 V
C) +0.15 V
D) +0.30 V
64) 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.
65) 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
66) When suspected drunk drivers are tested with a Breathalyzer, the alcohol (ethanol) in the exhaled
breath is oxidized to acetic acid with an acidic solution of potassium dichromate:
3 CH3CH2OH(aq) + 2 Cr2O7-2 (aq) + 16 H+(aq) 3CH3CO2H(aq) + 4Cr+3(aq) + 11H2O (l)
What is the value of E for the reaction when the concentrations of ethanol, acetic acid, Cr2O7-2, and Cr+3,
are 1.0M and the pH is 4.00? (Eº for this cell is 1.30V and the temperature is 298K).
Equations to solve this problem are below.
ε = ε° – lnQ
ε = 1.30 – ln
A) 1.62 V
B) 1.30 V
C) 0.98 V
D) 1.24 V
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 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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72) When a cell reaction reaches equilibrium,
A) E° = 0.
B) E = 0.
C) both E° and E = 0.
D) neither E° nor E = 0.
73) The equilibrium constant, K, can be calculated from
A) E°.
B) E.
C) either E° or E.
D) neither E° nor E.
74) 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
75) 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
76) 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)
77) 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).
78) Which statement below is not true?
A) The cell reactants in a fuel cell are continuously supplied from an external source.
B) A fuel cell is a galvanic cell.
C) Modern fuel cells can be easily regenerated using household current.
D) One of the reactants in a fuel cell is a traditional fuel.
79) Which of the following reactions is most suitable for a fuel cell?
A) MnO2(s) + Li(s) → LiMnO2(s)
B) Pb(s) + PbO2(s) + 2 H+(aq) + HSO4–(aq) → PbSO4(s) + 2 H2O(l)
C) HgO(l) + Zn(s) → ZnO(s) + Hg(l)
D) 2 CO(g) + O2(g) → 2 CO2(g)
80) Which of the following statements concerning a lithium battery is false?
A) A lithium battery is rechargeable.
B) A lithium battery has a relatively high voltage, due in part to the high oxidation potential of lithium.
C) It takes a small mass of lithium to provide one mole of electrons in the cell reaction.
D) The cell reaction produces toxic mercury, so the batteries should be recycled.
81) Shown below are the reactions occurring in the direct methanol fuel cell (DMFC).
I. 2 CH3OH(aq) + 2 H2O(l) → 2 CO2(g) +12 H+(aq) +12 e–
II. 3 O2(g) + 12 H+(aq) + 12 e– → 6 H2O(l)
Overall 2 CH3OH(aq) + 3 O2(g) → 2 CO2(g) + 4 H2O(l)
Which is the anode reaction, and what is being oxidized in the overall reaction?
A) I, CH3OH
B) I, H2O
C) II, O2
D) II, H+
82) Shown below are the reactions occurring in the proton-exchange membrane (PEM) fuel cell.
I. 2 H2(g) → 4 H+(aq) + 4 e–
II. O2(g) + 4 H+(aq) + 4 e– → 2 H2O(l)
Overall 2 H2(g) + O2(g) → 2 H2O(l)
Which is the cathode reaction, and what is being oxidized in the overall reaction?
A) I, H2
B) I, O2
C) II, H2
D) II, O2
83) Which of the following statements concerning the rusting of iron is false?
A) The oxidation site can occur at a different place on the metal surface than the reduction site.
B) The metal is reduced.
C) The rusting of iron requires both oxygen and water.
D) Salt increases the rate of corrosion by providing ions to carry the current.
84) What is least easily oxidized?
A) Al
B) Fe
C) Mg
D) Zn
85) Aluminum requires relatively little protection from corrosion because
A) aluminum has little tendency to react with oxygen.
B) the reduction potential for Al3+/Al is very low.
C) the oxidation of aluminum produces a hard, relatively impenetrable film of Al2O3.
D) aluminum is protected by cathodic protection.
86) A steel pipe can be protected from corrosion by attaching the pipe to a piece of magnesium because
A) magnesium forms a tight oxide coating.
B) magnesium is more easily oxidized than iron.
C) magnesium is inert.
D) magnesium and steel form a corrosion resistant alloy.
87) An electrolytic cell is
A) a battery.
B) a cell in which the cell reaction is spontaneous.
C) a cell in which an electric current drives a nonspontaneous reaction.
D) a cell in which reactants are continuously supplied to the cell.
31
88) Which statement is true?
A) The cathode is positive for a galvanic cell and negative for an electrolytic cell.
B) Electrons flow through the external circuit to the cathode in a galvanic cell and to the anode in an
electrolytic cell.
C) Oxidation occurs at the anode in a galvanic cell and at the cathode in an electrolytic cell.
D) Oxidation occurs at the cathode in a galvanic cell and at the anode in an electrolytic cell.
89) Which statement concerning overvoltage is false?
A) Overvoltage is the additional voltage above the calculated voltage required to bring about electrolysis.
B) Overvoltage is often due to a high activation energy for the reaction at one electrode.
C) Overvoltage is small for half-reactions involving the formation of O2(g) or H2(g).
D) Overvoltage must be experimentally determined.
90) O2(g) + 4 H+(aq) + 4 e–→ 2 H2O(l) E° = +1.23 V
I2(s) + 2 e– → 2 I–(aq) E° = +0.54 V
2 H2O(l) + 2 e– → H2(g) + 2 OH–(aq) E° = -0.83 V
Mg2+(aq) + 2 e– → Mg(s) E° = -2.37 V
Based on the data above, electrolysis of an aqueous solution of MgI2, with inert electrodes, is expected to
produce
A) Mg at the cathode and I2 at the anode.
B) H2 at the cathode and I2 at the anode.
C) Mg at the cathode and O2 at the anode.
D) H2 at the cathode and O2 at the anode.
91) O2(g) + 4 H+(aq) + 4 e– → 2 H2O(l) E° = +1.23 V
Pb2+(aq) + 2 e– → Pb(s) E° = -0.13 V
2 H2O(l) + 2 e– → H2(g) + 2 OH–(aq) E° = -0.83 V
Based on the half-reactions above, electrolysis of an aqueous solution of Pb(NO3)2 is expected to
produce.
A) Pb at the cathode and H2 at the anode.
B) Pb at the cathode and O2 at the anode.
C) H2 at the cathode and Pb at the anode.
D) O2 at the cathode and Pb at the anode.
92) The chlor-alkali industry is based on the electrolysis of aqueous NaCl. What are the products of this
electrolysis?
A) Na and Cl2
B) NaOH, H2, and O2
C) NaOH, H2, and Cl2
D) NaOH, O2, and Cl2
93) The Hall-Heroult process for the production of aluminum involves the electrolysis of
A) an aqueous solution of Al(NO3)3.
B) molten Al2O3.
C) molten cryolite, Na3AlF6.
D) a molten mixture of Al2O3 and Na3AlF6.
94) Which requires the most electricity (in terms of faradays of charge transferred) per gram of useful
product formed?
A) electrolysis of aqueous NaCl (chlor-alkali industry)
B) electrolysis of molten NaCl/CaCl2 in a Downs cell
C) electrorefining copper metal
D) production of aluminum in the Hall-Heroult process
95) Which of the following statements concerning the electrorefining of copper in not true?
A) The anode is constructed of chalcocite, Cu2S.
B) The anode mud is a valuable source of silver, gold, and platinum.
C) Copper is oxidized at the anode and copper(II) ions are reduced at the cathode.
D) The process is used to purify copper.
96) The gas OF2 can be produced from the electrolysis of an aqueous solution of KF, as shown in the
equation below.
OF2(g) + 2 H+(aq) + 4 e– → H2O(l) + 2 F–(aq) E° = +2.15 V
Using the given standard reduction potential, calculate the amount of OF2 that is produced, and the
electrode at which the OF2 is produced, upon the passage of 0.240 faradays through an aqueous KF
solution.
A) 3.24 g of OF2 at the anode
B) 13.0 g of OF2 at the anode
C) 3.24 g of OF2 at the cathode
D) 13.0 g of OF2 at the cathode
97) How many grams of chromium metal are plated out when a constant current of 8.00 A is passed
through an aqueous solution containing Cr3+ ions for 40.0 minutes?
A) 3.45 g
B) 6.15 g
C) 10.3 g
D) 31.0 g
98) How many grams of nickel metal are plated out when a constant current of 15.0 A is passed through
aqueous NiCl2 for 80.0 minutes?
A) 14.7 g
B) 21.9 g
C) 43.8 g
D) 48.4 g
99) How long must a constant current of 50.0 A be passed through an electrolytic cell containing aqueous
Cu2+ ions to produce 3.00 moles of copper metal?
A) 0.311 hours
B) 0.621 hours
C) 1.61 hours
D) 3.22 hours
100) Chromium can be electroplated from an aqueous solution containing sulfuric acid and chromic acid,
H2CrO4. What current is required to deposit chromium at a rate of 1.25 g/min?
A) 38.1 A
B) 38.7 A
C) 116 A
D) 232 A
101) A constant current is passed through a solution containing Cu2+(aq) resulting in the deposition of
4.40 g of Cu at the cathode. Assuming a current efficiency of 100%, if this same current is passed through
a solution of TcO4– for the same amount of time, how many grams of Tc would form at the cathode?
A) 0.969 g
B) 1.94 g
C) 6.78 g
D) 13.6 g
102) Fuel cells
A) produce carbon dioxide and hydrogen.
B) emit sulfur oxides.
C) are environmentally clean.
D) cannot be used in vehicles.
103) For the galvanic cell shown above, in what direction should the anions and cations in half–cell A
move?
A) The anions tend to move to the solid electrode and the cations into the salt bridge.
B) The anions tend to move into the salt bridge and the cations toward the solid electrode.
C) The anions tend to move toward the solid electrode and the cations should not move.
D) The cations tend to move toward the solid electrode and the anions should not move.
36
104) The cell reaction 2 Fe3+(aq) + Zn(s) → Zn2+(aq) + 2 Fe2+(aq) occurs in the galvanic cell shown above.
Where should the Fe3+(aq) and Fe2+(aq) be found?
A) Half-cell (A) contains Fe3+(aq) and half-cell (B) contains Fe2+(aq).
B) Half-cell (A) contains Fe2+(aq) and half-cell (B) contains Fe3+(aq).
C) Half-cell (A) contains Fe3+(aq) and Fe2+(aq).
D) Half-cell (B) contains Fe3+(aq) and Fe2+(aq).
105) The cell reaction 2 Fe3+(aq) + Zn(s) → Zn2+(aq) + 2 Fe2+(aq) occurs in the galvanic cell shown above.
Which would be the most appropriate choices for the solid electrode in half-cell (A) and in half-cell (B)?
A) Fe(s) for half-cell (A) and Zn(s) for half-cell (B)
B) Pt(s) for half-cell (A) and Zn(s) for half-cell (B)
C) Fe(s) for half-cell (A) and Fe(s) for half-cell (B)
D) Zn(s) for half-cell (A) and Pt(s) for half-cell (B)
Consider the galvanic cell shown below.
106) Identify the anode and cathode, and indicate the direction of Na+ ion and NO3– ion flow from the
salt bridge.
A) Al is the anode and Co is the cathode; Na+ ions flow into half-cell compartment (A) and NO3– ions
flow into half-cell compartment (B).
B) Al is the anode and Co is the cathode; NO3– ions flow into half-cell compartment (A) and Na+ ions
flow into half-cell compartment (B).
C) Co is the anode and Al is the cathode; Na+ ions flow into half-cell compartment (A) and NO3– ions
flow into half-cell compartment (B).
D) Co is the anode and Al is the cathode; NO3– ions flow into half-cell compartment (A) and Na+ ions
flow into half-cell compartment (B).
107) Identify the anode and cathode, and indicate the direction of ion flow to and from each electrode.
A) Al is the anode and Co is the cathode; Al3+ ions flow to the anode and Co2+ ions flow from the
cathode.
B) Al is the anode and Co is the cathode; Co2+ ions flow to the cathode and Al3+ ions flow from the
anode.
C) Co is the anode and Al is the cathode; Al3+ ions flow to the cathode and Co2+ ions flow from the
anode.
D) Co is the anode and Al is the cathode; Co2+ ions flow to the anode and Al3+ ions flow from the
cathode.
108) What is the balanced equation for the cell reaction?
A) 2 Al(s) + 3 Co(s) → 2 Al3+(aq) + 3 Co2+(aq)
B) 2 Al3+(aq) + 3 Co2+(aq) → 2 Al(s) + 3 Co(s)
C) 2 Al(s) + 3 Co2+(aq) → 2 Al3+(aq) + 3 Co(s)
D) 2 Al3+(aq) + 3 Co(s) → 2 Al(s) + 3 Co2+(aq)
109) What is the shorthand notation for the cell?
A) Al(s) | Al3+(aq) || Co(s) | Co2+(aq)
B) Al(s) | Al3+(aq) || Co2+(aq) | Co(s)
C) Co(s) | Co2+(aq) || Al(s) | Al3+(aq)
D) Co(s) | Co2+(aq) || Al3+(aq)| Al(s)
Consider the following galvanic cell.
110) Identify the anode and cathode, and indicate the direction of Na+ ion and NO3– ion flow from the
salt bridge.
A) Fe is the anode and Sn is the cathode; Na+ ions flow into half-cell compartment (A) and NO3– ions
flow into half-cell compartment (B).
B) Fe is the anode and Sn is the cathode; NO3– ions flow into half-cell compartment (A) and Na+ ions
flow into half-cell compartment (B).
C) Sn is the anode and Fe is the cathode; Na+ ions flow into half-cell compartment (A) and NO3– ions
flow into half-cell compartment (B).
D) Sn is the anode and Fe is the cathode; NO3– ions flow into half-cell compartment (A) and Na+ ions
flow into half-cell compartment (B).
111) Identify the anode and cathode, and indicate the direction of ion flow to and from each electrode.
A) Fe is the anode and Sn is the cathode; Fe2+ ions flow to the anode and Sn2+ ions flow from the
cathode.
B) Fe is the anode and Sn is the cathode; Sn2+ ions flow to the cathode and Fe2+ ions flow from the anode.
C) Sn is the anode and Al is the cathode; Fe2+ ions flow to the cathode and Sn2+ ions flow from the
anode.
D) Sn is the anode and Al is the cathode; Sn2+ ions flow to the anode and Fe2+ ions flow from the
cathode.
112) What is the balanced equation for the cell reaction?
A) Fe(s) + Sn(s) → Fe2+(aq) + Sn2+(aq)
B) Fe2+(aq) + Sn2+(aq) → Fe(s) + Sn(s)
C) Fe(s) + Sn2+(aq) → Fe2+(aq) + Sn(s)
D) Fe2+(aq) + Sn(s) → Fe(s) + Sn2+(aq)
113) What is the shorthand notation for the cell?
A) Fe(s) | Fe2+(aq) || Sn(s) | Sn2+(aq)
B) Fe(s) | Fe2+(aq) || Sn2+(aq) | Sn(s)
C) Sn(s) | Sn2+(aq) || Fe(s) | Fe2+(aq)
D) Sn(s) | Sn2+(aq) || Fe2+(aq) | Fe(s)