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ch 19 :( Flashcards

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1
Q

Calculate the cell potential at 25 °C for the following overall reaction.
Zn2+(aq) + 2 Fe2+(aq) → Zn(s) + 2 Fe3+(aq)
[Zn2+] = 1.50 × 10-4 M, [Fe3+] = 0.0200 M, and [Fe2+] = 0.0100 M. The standard reduction potentials are as follows:

Zn2+(aq) + 2 e– → Zn(s) E° = –0.763 V
Fe3+(aq) + e– → Fe2+(aq) E° = +0.771 V

A

a.

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2
Q

Write a balanced net ionic equation for the overall reaction represented by the following cell notation.
Cu(s) | Cu2+(aq) || Mn2+(aq) | Mn(s)

A

c.

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3
Q

Calculate the standard reduction potential for the given reaction at 25 °C.
AuCl4–(aq) + 3 e– → Au(s) + 4 Cl–(aq)
The thermodynamic information is as follows:
Au3+(aq) + 3 e– → Au(s) E° = +1.50 V
Au3+(aq) + 4 Cl–(aq) → AuCl4–(aq) Kf = 2.3 × 1025

A

c.

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4
Q

Explain the function of a salt bridge in a voltaic cell.

A

The salt bridge allows cations and anions to move between the two half-cells.

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5
Q

Which of the following statements concerning a voltaic cell is/are correct?
1. Oxidation occurs at an anode.
2. A voltaic cell consists of two half cells separated by a salt bridge.
3. Without a salt bridge, charge buildup will cause the cell reaction to stop

A

e.

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6
Q

The electrochemical reaction that powers a lead-acid storage battery is as follows:
Pb(s) + PbO2(s) + 4 H+(aq) + 2 SO42–(aq) → 2 PbSO4(s) + 2 H2O()

A

b.

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7
Q

Calculate the value of the equilibrium constant (K) at 25 °C for the following cell reaction:
Sn(s) + Pb2+(aq) → Sn2+(aq) + Pb(s); E°cell = 0.014 V

A

e.

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8
Q

The standard reduction potentials are as follows:
Cr3+(aq) + 3 e– → Cr(s); E° = –0.74 V

Fe2+(aq) + 2 e– → Fe(s); E° = –0.41 V

Calculate the standard Gibbs free energy change for the following reaction.

2 Cr(s) + 3 Fe2+ → 3 Fe(s) + 2 Cr3+(aq)

A

d.

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9
Q

Claculate the mass of chromium that can be deposited by electrolysis of an aqueous solution of chromium(III) sulfate, Cr2(SO4)3, for 180 min using a constant current of 11.0 A. Assume 100% current efficiency. (F = 96485 C/mol)

A

b.

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10
Q

A voltaic cell or galvanic cell converts chemical energy to electrical energy. for the given galvanic cell is –1.80 V.
Fe2+(aq) + 2 Cl–(aq) → Fe(s) + Cl2(g)

Calculate the value of ΔrG° for the reaction.

A

e.

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11
Q

Balance the following half-reaction occurring in a basic solution.
MnO2(s) → Mn(OH)2(s)

A

a.

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12
Q

Write a balanced net ionic equation for the reaction below in an acidic solution.
Cr2O72–(aq) + Ni(s) → Cr3+(aq) + Ni2+(aq)

A

a.

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13
Q

Which of the following is the balanced overall reaction and standard cell potential of an electrochemical cell constructed from half-cells with the given half reactions?
Pt2+(aq) + 2 e− → Pt(s); E° = 1.180 V

Pb2+(aq) + 2 e− → Pb(s); E° = –0.130 V

A

a.

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14
Q

Gold and platinum are commonly used as inert electrodes in laboratory experiments. In commercial applications, such as batteries, _____ is more commonly used as an inert electrodes because it is far less expensive.

A

graphite

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15
Q

Which of the following is true for a product-favored reaction at equilibrium?

A

a.

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16
Q

Which of the following statements is true for the following reaction, assuming the given reaction proceeds in the forward direction?
Fe3+(aq) + Co(s) → Fe2+(aq) + Co2+(aq)

A

c.

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17
Q

Calculate the copper(II) ion concentration at 25 °C in the cell Zn(s) | Zn2+(aq, 1.0 M) || Cu2+(aq) | Cu(s) if the measured cell potential is 1.06 V. The standard cell potential is 1.10 V.

A

c.

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18
Q

According to the cell notation below, which of the following species is undergoing reduction?
Ni | Ni2+(aq) || Mn2+(aq) | MnO2(s) | Pt(s)

A

d.

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19
Q

Calculate Ecell for the following electrochemical cell at 25°C. The standard cell potential, E°cell, is 0.460 V.
Cu(s) | Cu2+(aq, 0.016 M) || Ag+(aq, 0.11 M) | Ag(s)

A

a.

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20
Q

In the given electrochemical cell, which of the following is the cathode half-reaction?
Zn(s) | Zn2+(aq) || Fe3+(aq), Fe2+(aq) | Pt(s)

A

a.

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21
Q

Calculate Ecell for the following electrochemical cell at 25 °C
Pt(s) | H2(g, 1.00 atm) | H+(aq, 1.00 M) || Sn2+(aq, 0.350 M), Sn4+(aq, 0.020 M) | Pt(s)
The standard reduction potentials are as follows:
Sn4+(aq) + 2 e– → Sn2+(s) E° = +0.15 V
2 H+(aq) + 2 e– → H2(g) E° = 0.00 V

A

c.

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22
Q

The unit for electromotive force, emf, is the volt. 1 volt is equal to _____.

A

c.

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23
Q

Calculate for the electrochemical cell Ag(s) | AgCl(s) | Cl–(aq, 1.0 M) || Cu2+(aq, 1.0 M) | Cu(s).
The standard reduction potentials are as follows:

Cu2+(aq) + 2 e– → Cu(s) E° = +0.337 V
AgCl(s) + e– → Ag(s) + Cl–(aq) E° = +0.222 V

A

c.

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24
Q

An SHE electrode has been assigned a standard reduction potential, E°, of 0.00 volts. Which of the following reactions will occur at this electrode?

A

e.

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25
Q

The standard reduction potentials for a reaction are as follows:
Pb2+(aq) + 2 e– → Pb(s) E° = –0.126 V
PbSO4(s) + 2 e– → Pb(s) + SO42–(aq) E° = –0.355 V
Calculate the Ksp for lead(II)sulfate (PbSO4) at 25 °C.

A

b.

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26
Q

In the context of the diagram given below, which of the following statements is true concerning half-cell II?

A

a.

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27
Q

Which of the following equations represents the Nernst equation?

A

a.

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28
Q

Calculate the charge, in coulombs, is required to deposit 1.5 g of solid magnesium from a solution of Mg2+(aq) ion.

A

c.

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29
Q

Write a balanced chemical equation for the oxidation of solid cadmium by concentrated nitric acid, producing nitrogen dioxide gas and Cd2+(aq) ion.

A

d.

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30
Q

Which of the following is the cell notation for a cell in which the hydrogen electrode is the anode and the cathode half-reaction is Co3+(aq) + e− → Co2+(aq)?

A

a.

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31
Q

One Faraday is defined as the:

A

b.

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32
Q

Which of the following statements is true for electron transfer reactions?

A

a.

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33
Q

If an electric current is passed through a solution of molten potassium bromide, KBr, the product at the cathode is _____.

A
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34
Q

Calculate E°cell for the cell for the reaction 2 Ga(s) + 3 Sn4+(aq) → 3 Sn2+(aq) +2 Ga3+(aq).

A

a.

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35
Q

For the electrochemical cell Cu(s) | Cu2+ || Ag+ | Ag(s), the standard cell potential is 0.46 V. A cell using these reagents was made, and the observed potential was 0.26 V at 25 oC. Which of the following is a possible explanation for the observed voltage?

A

c.

36
Q

In an electrolytic cell, reduction occurs at the _____ and oxidation occurs at the _____.

A

cathode; anode

37
Q

Write the balanced oxidation half-reaction for the following overall reaction:
2 H+(aq) + Ca(s) → Ca2+(aq) + H2(g)

A

a.

38
Q

Consider the following half-reactions.
Ag+(aq) + e– → Ag(s) E° = +0.80 V
Cu2+(aq) + 2 e– → Cu(s) E° = +0.34 V
Pb2+(aq) + 2 e– → Pb(s) E° = –0.13 V
Fe2+(aq) + 2 e– → Fe(s) E° = –0.44 V
Al3+(aq) + 3 e– → Al(s) E° = –1.66 V
Which of the following species will oxidize lead, Pb(s)?

A

a.

39
Q

Consider the following half-reactions.
Cl2(g) + 2 e– → 2 Cl–(aq) E° = +1.36 V
Ag+(aq) + e– → Ag(s) E° = +0.80 V
Cu2+(aq) + 2 e– → Cu(s) E° = +0.34 V
Sn2+(aq) + 2 e– → Sn(s) E° = –0.14 V
Al3+(aq) + 3 e– → Al(s) E° = –1.66 V
Which of the following species will reduce Cu2+(aq) ion?

A

d.

40
Q

The standard cell potential of the given electrochemical cell is 0.19 V.
Pt | Sn4+(aq, 1.0 M), Sn2+(aq, 1.0 M) || Cu2+(aq, 0.200 M) | Cu

Which of the following factors will increase the measured cell potential of the given electrochemical cell?

A

e.

41
Q

When a secondary battery provides electrical energy, it is acting as a voltaic cell. When the battery is recharging, it is operating as a(n) _____ cell.

A

voltaic?

42
Q

Which of the following are standard conditions for an electrochemical cell?
1. Solutes in aqueous solution have a concentration of 1.0 M.
2. Gaseous reactants or products have a pressure of 1 bar.
3. Solids are present in quantities of 1 mole.

A

not e. or a.

43
Q

Calculate ΔrG° for the disproportionation reaction of copper(I) ion (Cu+) at 25 °C.
2 Cu+(aq) → Cu2+(aq) + Cu(s)
The standard reduction potentials are as follows:
Cu+(aq) + e– → Cu(s) E° = +0.518 V
Cu2+(aq) + 2 e– → Cu(s) E° = +0.337 V

A

c.

44
Q

Calculate the value of the reaction quotient, Q, for the voltaic cell constructed from the following two half-reactions when the Zn2+ion concentration is 0.0110 M and the Ag+ ion concentration is 1.27 M?

A

b.

45
Q

Which of the following species are likely to behave as oxidizing agents?
Li(s), H2(g), MnO4–(aq), and Cl–(aq)

A

b.

46
Q

How many electrons are transferred in the given reaction?
Ni + 2 HCl → Ni Cl2 + H2

A

c.

47
Q

Balance the following half-reaction occurring in an acidic solution.
NO3–(aq) → NO(aq)

A

a.

48
Q

Write a balanced net ionic equation for the overall reaction represented by the following cell notation.
Al(s) | Al3+(aq) || Cl2(g) | Cl–(aq) | Pt(s)

A

a.

49
Q

The use of electrical energy to produce chemical change is known as _____. An example of this process is the reduction of sodium chloride, NaCl(), to produce solid sodium.

A

electrochemistry

50
Q

Given the following two half-reactions, write the overall reaction in the direction in which it is product-favored, and calculate the standard cell potential.
Pb2+(aq) + 2 e– → Pb(s) E° = –0.126 V
Fe3+(aq) + e– → Fe2+(s) E° = +0.771 V

A

d.

51
Q

Calculate the equilibrium constant for the reaction below at 25 °C.
Co(s) + 2 Cr3+(aq) → Co2+(aq) + 2 Cr2+(aq)
The standard reduction potentials are as follows:

Co2+(aq) + 2 e– → Co(s) E° = –0.28 V
Cr3+(aq) + e– → Cr2+(aq) E° = –0.41 V

A

a.

52
Q

Use the following standard reduction potentials to determine which species is the best oxidizing agent.
O2(g) + 4 H+(aq) + 4 e– → 2 H2O() E° = +1.229 V
Hg22+(aq) + 2 e– → 2 Hg() E° = +0.789 V
I2(s) + 2 e– → 2 I–(aq) E° = +0.535 V

A

b.

53
Q

Which of the following statements is true concerning the voltaic cell shown below?

A

a.

54
Q

Which of the following reactions will require the use of an inert electrode when used in a voltaic cell?

A

d.

55
Q

Balance the following oxidation–reduction reaction occurring in an acidic solution.
MnO4–(aq) + Cr2+(aq) → Mn2+(aq) + Cr3+(aq)

A

not b. or c.

56
Q

For the following cell reaction, the standard cell potential is 1.34 V. To determine the cell potential at nonstandard conditions, what is the value that should be used for n in the Nernst equation?

A

b.

57
Q

Use the following standard reduction potentials to determine which species is the strongest reducing agent.
2 H+(aq) + 2 e– → H2(g); 0.00 V
K+(aq) + e– → K(s); –2.93 V

F2(g) + 2 e– → 2 F–(aq); 2.87 V
Al3+(aq) + 3 e– → Al(s); –1.66 V
Pb2+(aq) + 2 e– → Pb(s); –0.13 V

A

e.

58
Q

What half-reaction occurs at the cathode during the electrolysis of molten potassium bromide?

A

d.

59
Q

Use the following standard reduction potentials to determine which species is the strongest oxidizing agent.
Fe2+(aq) + 2e– → Fe(s); E° = –0.41 V

Pt2+(aq) + 2 e– → Pt(s); E° = 1.18 V

Cr2O72–(aq) + 14 H+(aq) + 6 e– → 2 Cr3+(aq) + 7 H2O(); E° = 1.33 V

A

a.

60
Q

The following electrochemical cell has a potential of +0.326 V at 25 °C.
Pt | H2(g, 1.00 atm) | H+(aq, 1.00 M) || Cl–(aq) | AgCl(s) | Ag

The standard reduction potential, E°, of AgCl(s) is +0.222 V. Calculate the Cl–(aq) ion concentration.

A

c.

61
Q

Which of the following is the cell notation for a voltaic cell based on the following reaction?
Cu2+(aq) + Pb(s) + SO42–(aq) → Cu(s) + PbSO4(s)

A

e.

62
Q

Which of the following statements is true concerning the electrochemical cell Zn(s) | Zn2+(aq, 1.0 M) || Ca2+(aq, 1.0 M) | Ca(s)
The standard reduction potentials are given follows:

Zn2+(aq) + 2 e− → Zn(s); E° = –0.76 V

Ca2+(aq) + 2 e− → Ca(s); E° = –2.87 V

A

not d. or e. or c.

63
Q

Write the balanced reduction half-reaction for the following overall reaction:
2 Fe(s) + 3 Cl2(aq) → 2 Fe3+(aq) + 6 Cl–(aq)

A

a.

64
Q

Calculate the standard cell potential ( ) for the reaction 2 Ag(s) + Co2+(aq) → 2 Ag+(aq) + Co(s).
The standard reduction potentials are as follows:
Ag+(aq) + e−→ Ag(s) E° = 0.8 V
Co2+(aq) +2 e−→ Co(s) E° = –0.277 V

A

a.

65
Q

Calculate the equilibrium constant for the following reaction at 25 °C,
2 IO3–(aq) + 5 Hg() + 12 H+(aq) → I2(s) + 5 Hg2+(aq) + 6 H2O()
The standard reduction potentials are as follows:
IO3–(aq) + 6 H+(aq) + 5 e– → I2(s) + 3 H2O() E° = +1.20 V
Hg2+(aq) + 2 e– → Hg() E° = +0.86 V

A

not b. or c.

66
Q

How many moles of electrons are produced from a current of 17.0 A in 3.40 hours?

A

b.

67
Q

A current of 12.0 A is passed through molten magnesium chloride for 14.0 h. How many moles of magnesium metal can be produced from this electrolysis?

A

b.

68
Q

Calculate Ecell for the following electrochemical cell at 25 °C.
Pt(s) | Fe3+(aq, 0.100 M), Fe2+(aq, 0.040 M) || Cl–(aq, 0.50 M) | AgCl(s) | Ag(s)
The standard reduction potentials are as follows:
AgCl(s) + e– → Ag(s) + Cl–(aq) E° = +0.222 V
Fe3+(aq) + e– → Fe2+(aq) E° = +0.771 V

A

not b. or c. or a.

69
Q

When the given oxidation–reduction reaction in an acidic solution is balanced, what is the lowest whole-number coefficient for H+, and on which side of the balanced equation should it appear?
MnO4–(aq) + Br–(aq) → Mn2+(aq) + Br2(l)

A

d.

70
Q

If the = –0.362 V for a given electrochemical cell at 25 °C, calculate the pH of the solution at the cathode.
Pt | H2(g, 1.0 atm) | H+(aq, 1.00 M) || H+(aq) | H2(g, 1.0 atm) | Pt

A

c.

71
Q

The cell potential of the following electrochemical cell is determined by using an unspecified concentration of acid. Calculate the pH of the acid solution, given that the measured cell potential is –0.431 V and the anode reduction potential (E°) is 0.222 V at 25 °C.

A

a.

72
Q

Which of the following statements concerning voltaic cells is not true?

A

b.

73
Q

When the following oxidation–reduction reaction in acidic solution is balanced, what is the lowest whole-number coefficient for Na+(aq) ion?
Na(s) + Ca2+(aq) → Na+(aq) + Ca(s)

A

e.

74
Q

The value of E°cell is for the following reaction:
Cl2(g) + 2 Fe2+(aq) → 2 Fe3+(aq) + 2 Cl–(aq)

Calculate the value of E°cell for the reaction below.

Cl–(g) + Fe3+(aq) → Fe2+(aq) + ½ Cl2(g)

A

not b. or c. or a.

75
Q

Aluminum(III) ion (Al3+) is reduced to solid aluminum at an electrode. If a current of 2.75 amperes is passed for 36 hours, calculate the mass of aluminum deposited at the electrode. (Assume 100% current efficiency.)

A

b.

76
Q

The following has a potential of 0.34 V.

If the concentrations of each of the ions is 1.0 M and the pressure of H2 is 1.0 atm, then E° for the half-reaction is _____.

A

c.

77
Q

Write a balanced chemical equation for the following reaction in a basic solution.
ClO–(aq) + Cr(OH)3(s) → Cl–(aq) + CrO42–(aq)

A

a.

78
Q

Primary batteries are also called storage batteries or rechargeable batteries. Is this statement true or false?

A

false

79
Q

Write a balanced half-reaction for the reduction of hydrogen peroxide to water in an acidic solution.

A

c.

80
Q

Which of the following overall chemical equations is responsible for generating electricity in fuel cells used in NASA’s Space Shuttle programs?

A

d.

81
Q

Which of the following are the expected products when an aqueous solution of lithium sulfate is electrolyzed?
Reduction Half-Reaction

E° (V)

Li+(aq) + e– → Li(s)
–3.04

2 H2O(l) + 2 e– → H2(g) + 2 OH–(aq)
–0.83

2 H+(aq) + 2 e– → H2(g)
0.00

O2(g) + 4 H+(aq) + 4 e– → 2 H2O(l)
1.23

S2O82–(aq) + 2 e– → 2 SO42–(aq)
2.01

A

not c. or d. or a.

82
Q

Calculate for the electrochemical cell Pb(s) |PbCl2(s) | Cl–(aq, 1.0 M) || Fe3+(aq, 1.0 M), Fe2+(aq, 1.0 M) | Pt(s).
The standard reduction potentials are as follows:
Pb2+(aq) + 2 e– → Pb(s) E° = –0.126 V
PbCl2(s) + 2 e– → Pb(s) + 2 Cl–(aq) E° = –0.267 V
Fe3+(aq) + e– → Fe2+(aq) E° = +0.771 V
Fe2+(aq) + e– → Fe(s) E° = –0.44 V

A

d.

83
Q

If ΔrG° for the following reaction is –22.2 kJ/mol-rxn, calculate for the following reaction:
Cu2+(aq) + 2 Ag(s) + 2 Cl–(aq) → Cu(s) + 2 AgCl(s)

A

c.

84
Q

Which of the following statements is/are correct?
1. A nickel-cadmium battery is an example of a secondary or rechargeable battery that is often used in rechargeable cordless appliances.
2. Hydrogen-oxygen fuel cells use the heat of combustion of hydrogen to recharge lead storage batteries.
3. LeClanché cells are the most efficient rechargeable batteries, but they are rarely used because of their high cost of production.

A

a.

85
Q

Write a balanced half-reaction for the reduction of CrO42–(aq) to Cr(OH)3(s) in a basic solution.

A

not b.

86
Q

Which of the following statements is true for the following reaction, assuming the given reaction proceeds in the forward direction?
3 Sn4+(aq) + 2 Cr(s) → 3 Sn2+(aq) + 2 Cr3+(aq)

A

not c. or a.

87
Q

Batteries used in watches contain mercury(II) oxide. As the current flows, mercury(II) oxide is reduced to mercury according to the following reaction:

A

not d.

Chem II (13 decks)

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