Deck 20: Principles of Chemical Reactivity: Electron Transfer Reactions

Question 1

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) 1; reactant side
B) 2; product side
C) 8; reactant side
D) 16; reactant side
E) 4; product side

Answer 1

16; reactant side

Question 2

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

A) MnO₂(s) + 2 H₂O(l) + 2e−→ Mn(OH)₂(s)+ 2 OH−(aq)
B) MnO₂(s) + 2 H₂O(l) + 4e−→ Mn(OH)₂(s)+ (OH)₂−(aq)
C) MnO₂(s) + H₂²⁺(aq) + 2e−→ Mn(OH)₂(s)
D) MnO₂(s) + H₂(g) → Mn(OH)₂(s) + 2 e−
E) MnO₂(s) + 2 H₂O(l) → Mn(OH)₂(s)+ 2 OH−(aq)

Answer 2

MnO₂(s) + 2 H₂O(l) + 2e−→ Mn(OH)₂(s)+ 2 OH−(aq)

Question 3

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

A) Cl₂(aq) + 2 e^- → 2 Cl^-(aq)
B) Fe(s) + 3 e- → Fe3+(aq)
C) Fe(s) + Cl2(aq) → FeCl3(aq)
D) Cl2(aq) → 2 Cl-(aq) + 2 e-
E) 3 Cl2(aq) + 2 e- → 2 Cl-(aq)

Answer 3

Cl₂(aq) + 2 e^- → 2 Cl^-(aq)

Question 4

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) 5
B) 4
C) 1
D) 3
E) 2

Question 5

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

A) MnO₄^-(aq) + 8 H⁺(aq) + 5 Cr²⁺(aq) → Mn²⁺(aq) + 4 H₂O(l) + 5 Cr³⁺(aq)
B) MnO₄^-(aq) + 8 H⁺(aq) + Cr²⁺(aq) → Mn²⁺(aq) + 4 H₂O(l) + Cr³⁺(aq)
C) MnO₄^-(aq) + 4 H₂(g) + 5 Cr²⁺(aq)→ Mn²⁺(aq) + 4 H₂O(l) + 5 Cr³⁺(aq)
D) MnO₄^-(aq) + 8 H⁺(aq) + 2 Cr²⁺(aq) → Mn²⁺(aq) + 4 H₂O(l) + 2 Cr³⁺(aq)
E) MnO₄^-(aq) + Cr²⁺(aq) → Mn²⁺(aq) + 2 O₂(g) + Cr³⁺(aq)

Question 6

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

A) Co(s) + 2 Ag⁺(aq) → 2 Ag(s) + Co²⁺(aq)
B) 3 Ni(s) + 2 Au³⁺(aq) → 3 Ni²⁺ + 2 Au(s)
C) Cu(s) + 2 Ag⁺(aq) → Cu²⁺(aq) + 2 Ag(s)
D) Zn(s) + 2 MnO₂(s) + 2 NH₄⁺(aq) → Zn²⁺(aq) + Mn₂O₃(s) + 2 NH₃(aq) + H₂O(l)
E) 3 Zn²⁺(aq) + 2 Al(s) → 3 Zn(s) + 2 Al³⁺(aq)

Question 7

Which of the following is the cell notation for a voltaic cell based on the following reaction? Cu²⁺(aq) + Fe(s) → Cu(s) + Fe²⁺(aq)

A) Cu(s) | Cu²⁺(aq) || Fe²⁺(aq) | Fe(s)
B) Fe(s) || Fe²⁺(aq), Cu²⁺(aq) | Cu(s)
C) Cu(s) || Cu²⁺(aq), Fe²⁺(aq) || Fe(s)
D) Cu(s) | Fe²⁺(aq) || Cu²⁺(aq) | Fe(s)
E) Fe(s) | Fe²⁺(aq) || Cu²⁺(aq) | Cu(s)

Question 8

Write a balanced half-reaction for the reduction of CrO₄^2-(aq) to Cr(OH)₃(s) in a basic solution.

A) CrO₄^2-(aq) + 3 OH^-(aq) + 3 e^- ? Cr(OH)₃(s) + 2 O₂(g)
B) CrO₄^2-(aq) + 3 H⁺(aq) + 3 e^- ? Cr(OH)₃(s)
C) CrO₄^2-(aq) + 3 H⁺(aq) ? Cr(OH)₃(s) + 2 e^-
D) CrO₄^2-(aq) + 4 H₂O( $\ell$ ) + 3 e^- ? Cr(OH)₃(s) + 5 OH^-(aq)
E) CrO₄^2-(aq) + 3 OH^-(aq) ? Cr(OH)₃(s) + 2 O₂(g)

Question 9

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

A) A salt bridge allows cations and anions to move between half-cells.
B) Electrons flow from a cathode to an anode in the external circuit.
C) Oxidation occurs at an anode.
D) A voltaic cell can be used as a source of energy.
E) A voltaic cell consists of two half-cells.

Question 10

Write a balanced chemical equation for the following reaction in a basic solution.
ClO^-(aq) + Cr(OH)₃(s) ? Cl^-(aq) + CrO₄^2-(aq)

A) 3 ClO^-(aq) + 2 Cr(OH)₃(s) + 4 OH^-(aq) ? 3 Cl^-(aq) + 2 CrO₄^2-(aq) + 5 H₂O( $\ell$ )
B) ClO^-(aq) + Cr(OH)₃(s) + 3 OH^-(aq) ? Cl^-(aq) + CrO₄^2-(aq) + 3 H₂O( $\ell$ )
C) 2 ClO^-(aq) + 3 Cr(OH)₃(s) + 3 OH^-(aq) ? 2 Cl^-(aq) + 3 CrO₄^2-(aq) + 6 H₂O( $\ell$ )
D) 4 ClO^-(aq) + Cr(OH)₃(s) + 4 OH^-(aq) ? Cl^-(aq) + CrO₄^2-(aq) + 6 H₂O( $\ell$ )
E) ClO^-(aq) + Cr(OH)₃(s) ? Cl^-(aq) + CrO₄^2-(aq) + 3 H⁺(aq)

Question 11

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

A) Ca(s) → 2e^- + Ca²⁺ (aq)
B) 2 H⁺(aq) → H₂(g) + 2 e^-
C) H₂(g) → 2 H⁺(aq) + 2 e^-
D) Ca(s) + 2 e^- → Ca²⁺(aq)
E) 2Ca(s) → Ca²⁺(aq) + 2 e^-

Question 12

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) Fe³⁺(aq) is oxidized and Co(s) is reduced.
B) Fe³⁺(aq) is oxidized and Co²⁺(aq) is reduced.
C) Co(s) is oxidized and Fe³⁺(aq) is reduced.
D) Co(s) is oxidized and Co²⁺(aq) is reduced.
E) Fe²⁺(aq) is oxidized and Co(s) is reduced.

Question 13

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

A) HNO₃(aq) + Cd(s) ? Cd²⁺(aq) + NO₂(g) + OH^-(aq)
B) 2 HNO₃(aq) + Cd(s) ? Cd²⁺(aq) + 2 NO₂(g) + 2 OH^-(aq)
C) HNO₃(aq) + Cd(s) + H⁺(aq) ? Cd²⁺(aq) + NO₂(g) + H₂O( $\ell$ )
D) 4 HNO₃(aq) + Cd(s) ? Cd²⁺(aq) + 2 NO₂(g) + 2 H₂O( $\ell$ ) + 2 NO₃^-(aq)
E) HNO₃(aq) + Cd(s) ? Cd²⁺(aq) + NO₂(g)

Question 14

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

A) 0
B) 1
C) 2
D) 3
E) 4

Question 15

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) Sn⁴⁺(aq) is the reducing agent and Cr(s) is the oxidizing agent.
B) Cr(s) is the reducing agent and Sn²⁺(aq) is the oxidizing agent.
C) Sn⁴⁺(aq) is the reducing agent and Sn²⁺(aq) is the oxidizing agent.
D) Cr(s) is the reducing agent and Cr³⁺(aq) is the oxidizing agent.
E) Cr(s) is the reducing agent and Sn⁴⁺(aq) is the oxidizing agent.

Question 16

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

A) 2 H₂O₂( $\ell$ ) ? 2 H₂O( $\ell$ ) + O₂(g)
B) 2 H₂O₂( $\ell$ ) + 2e^- ? 2 H₂O( $\ell$ ) + O₂(g)
C) H₂O₂( $\ell$ ) + 2 H⁺(aq) + 2 e^- ? 2 H₂O( $\ell$ )
D) H₂O₂( $\ell$ ) + 4 H⁺(aq) + 2 e^- ? 2 H₂O( $\ell$ ) + H₂(g)
E) H₂O₂( $\ell$ ) + 2 H⁺(aq) + 4 e^- ? 2 H₂(g) + O₂(g)

Question 17

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

A) [Cu²⁺] decreases with time, and [K+] increases with time.
B) [Cu²⁺] increases with time, and [K+] increases with time.
C) [Cu²⁺] decreases with time, and [K+] decreases with time.
D) [Cu²⁺] decreases with time, and [SO₄2-] decreases with time.
E) [Cu²⁺] increases with time, and [SO₄2-] increases with time.

Question 18

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

A) NO₃^-(aq) + 4 H+(aq) + 3 e− → NO(g) + 2 H₂O(l)
B) NO₃^-(aq) + 2 H₂O(l) + 3 e− → NO(g) + 4 H+(aq)
C) NO₃^-(aq) + 4 H+(aq) → NO(g) + 2 H₂O(l) + 3 e−
D) NO₃^-(aq) + 3 e− → NO(g) + 4 H+(aq) + 2 H₂O(l)
E) NO₃^-(aq) + 4 H+(aq)→ NO(g) + 2 H₂O(l)

Question 19

Write a balanced net ionic equation for the reaction below in an acidic solution.
Cr₂O₇^2-(aq) + Ni(s) ? Cr³⁺(aq) + Ni²⁺(aq)

A) Cr₂O₇^2-(aq) + 3 Ni(s) + 14 H⁺(aq) ? 2 Cr³⁺(aq) + 3 Ni²⁺(aq) + 7 H₂O( $\ell$ )
B) Cr₂O₇^2-(aq) + Ni(s) + 14 H⁺(aq) ? 2 Cr³⁺(aq) + Ni²⁺(aq) + 7 H₂O( $\ell$ ).
C) Cr₂O₇^2-(aq) + 3 Ni(s) ? 2 Cr³⁺(aq) + 3 Ni²⁺(aq) + O^2-(aq)
D) Cr₂O₇^2-(aq) + Ni(s) + 14 H⁺(aq) ? 2 Cr³⁺(aq) + Ni²⁺(aq) + 7 H₂O( $\ell$ )
E) Cr₂O₇^2-(aq) + 3 Ni(s) + 7 H⁺(aq) ? 2 Cr³⁺(aq) + 3 Ni²⁺(aq) + 7 OH^-(aq)

Question 20

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

A) The Zn anode mass decreases as the cell discharges.
B) The Zn cathode mass increases as the cell discharges.
C) The Zn cathode mass decreases as the cell discharges.
D) The Zn anode mass increases as the cell discharges.
E) The mass of the Zn electrode neither increases nor decreases as the cell discharges.

Question 21

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) 2 Cu(s) + Mn²⁺(aq) → Mn(s) + 2 Cu²⁺(aq)
B) Cu(s) + Cu²⁺(aq) → Mn(s) + Mn²⁺(aq)
C) Cu(s) + Mn²⁺(aq) → Mn(s) + Cu²⁺(aq)
D) 2 Mn(s) + Cu²⁺(aq) → Cu(s) + 2Mn²⁺(aq)
E) Mn(s) + Cu²⁺(aq) → Cu(s) + Mn²⁺(aq)

Question 22

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) Pb²⁺(aq) + 2 Fe²⁺(s) ? Pb(s) + 2 Fe³⁺(aq); $E _ { \text {cell } } ^ { \circ }$ = +0.897 V
B) Pb²⁺(aq) + Fe²⁺(s) ? Pb(s) + Fe³⁺(aq); $E _ { \text {cell } } ^ { \circ }$ = +0.645 V
C) Pb(s) + 2 Fe³⁺(aq) ? Pb²⁺(aq) + 2 Fe²⁺(s); $E _ { \text {cell } } ^ { \circ }$ = +1.416 V
D) Pb(s) + 2 Fe³⁺(aq) ? Pb²⁺(aq) + 2 Fe²⁺(s); $E _ { \text {cell } } ^ { \circ }$ = +0.897 V
E) Pb(s) + Fe³⁺(aq) ? Pb²⁺(aq) + Fe²⁺(s); $E _ { \text {cell } } ^ { \circ }$ = +0.645 V

Question 23

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) Ag⁺(aq) and Cu²⁺(aq)
B) Ag(s) and Cu(s)
C) Fe²⁺(aq) and Al³⁺(aq)
D) Fe(s) and Al(s)
E) Cu²⁺(aq) and Fe²⁺(aq)

Question 24

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

A) Mn²⁺(aq)
B) Ni²⁺(aq)
C) Ni(s)
D) MnO₂(s)
E) Pt(s)

Question 25

Use the following standard reduction potentials to determine which species is the best oxidizing agent.
$$\begin{array} { l l } \mathrm { O } _ { 2 } ( \mathrm {~g} ) + 4 \mathrm { H } ^ { + } ( \mathrm { aq } ) + 4 \mathrm { e } ^ { - } \rightarrow 2 \mathrm { H } _ { 2 } \mathrm { O } ( \ell ) & E ^ { \circ } = + 1.229 \mathrm {~V} \\\mathrm {{ Hg } _ { 2 }} ^ { 2 + } ( \mathrm { aq } ) + 2 \mathrm { e } ^ { - } \rightarrow 2 \mathrm { Hg } ( \ell ) & E ^ { \circ } = + 0.789 \mathrm {~V} \\\mathrm { I } _ { 2 } ( \mathrm {~s} ) + 2 \mathrm { e } ^ { - } \rightarrow 2 \mathrm { I } ^ { - } ( \mathrm { aq } ) & E ^ { \circ } = + 0.535 \mathrm {~V}\end{array}$$

A) I₂(s)
B) O₂(g)
C) I^-(aq)
D) Hg₂²⁺(aq)
E) H₂O( $\ell$ )

Question 26

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) Pt(s) | H₂(g) | H⁺(aq) || Co³⁺(aq), Co²⁺(aq) | Pt(s)
B) Pt(s) | H₂(g) | H⁺(aq) || Co³⁺(aq), Co²⁺(aq)
C) Co²⁺(aq), Co³⁺(aq) || H⁺(aq) | H₂(g) | Pt(s)
D) Pt(s)| Co²⁺(aq), Co³⁺(aq) || H⁺(aq) | H₂(g) | Pt(s)
E) H₂(g) | H⁺(aq) || Co²⁺(aq), Co³⁺(aq)

Question 27

Which of the following is the cell notation for a voltaic cell based on the following reaction? Cu²⁺(aq) + Pb(s) + SO₄^2-(aq) → Cu(s) + PbSO₄(s)

A) Pb(s) | PbSO₄(s) || Cu²⁺(aq) || Cu(s)
B) Cu(s) | Cu²⁺(aq) || SO₄^2-(aq) | PbSO₄(s) | Pb(s)
C) Cu(s) | Cu²⁺(aq), SO₄^2-(aq) | PbSO₄(s) | Pb(s)
D) Cu(s) | Cu²⁺(aq), SO₄^2-(aq) || PbSO₄(s) || Pb(s)
E) Pb(s) | PbSO₄(s) | SO₄^2-(aq) || Cu²⁺(aq) || Cu(s)

Question 28

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) Fe³⁺(aq) + e− → Fe²⁺(aq)
B) Fe²⁺(aq) + e− → Fe³⁺(aq)
C) Fe²⁺(aq) + Pt(s) → Fe³⁺(aq) + e−
D) Zn²⁺(aq) → Zn(s) + 2 e−
E) Zn(s) → Zn²⁺(aq) + 2 e−

Question 29

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) Pt²⁺(aq) + Pb(s)? Pt(s) + Pb²⁺(aq); $E _ { \text {cell } } ^ { \circ }$ = 1.310 V
B) Pt(s) + Pb²⁺(aq) ? Pt²⁺(aq) + Pb(s); $E _ { \text {cell } } ^ { \circ }$ = ?1.310 V
C) Pt²⁺(aq) + Pb²⁺(aq) ? Pt(s) + Pb(s); $E _ { \text {cell } } ^ { \circ }$ = 1.050 V
D) Pt²⁺(aq) + Pb(s) ? Pt(s) + Pb²⁺(aq); $E _ { \text {cell } } ^ { \circ }$ =0.655 V
E) Pt(s) + Pb²⁺(aq) ? Pt²⁺(aq) + Pb(s); $E _ { \text {cell } } ^ { \circ }$ = ?0.655 V

Question 30

Calculate the standard cell potential ( $E _ { \text {cell } } ^ { \circ }$ ) 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) -1.077 V
B) 1.077 V
C) -1.877 V
D) 1.877 V
E) 1.323 V

Question 31

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) 2 Al(s) + 3 Cl₂(g) → 2 Al³⁺(aq) + 6 Cl^-(aq)
B) Al(s) + Al³⁺(aq) → Cl^-(aq) + Cl₂(g)
C) 2 Al³⁺(aq) + 6 Cl^-(aq) → 2 Al(s) + 3 Cl₂(g)
D) Al(s) + 3 Cl₂(g) → Al³⁺(s) + 2 Cl^-(aq)
E) Al(s) + 2 Cl^-(aq) → Cl₂(g) + Al³⁺(aq)

Question 32

Calculate $E _ { \text {cell } } ^ { \circ }$ 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) -0.115 V
B) -0.107 V
C) +0.115 V
D) +0.452 V
E) +0.559 V

Question 33

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) 2 H₂O( $\ell$ ) + 2 e^- ?H₂(g) + 2 OH^-(aq)
B) O₂(g) + 4 e^- ? 2 O^2-(aq)
C) Hg₂Cl₂(s) + 2 e^- ? 2 Hg( $\ell$ ) + 2 Cl^-(aq)
D) Li⁺(aq) + e^- ? Li(s)
E) 2 H⁺(aq) + 2 e^- ? H₂(g)

Question 34

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) Ag(s) and Sn²⁺(aq)
B) Cl^-(aq) and Ag(s)
C) Cl₂(g) and Ag⁺(aq)
D) Sn(s) and Al(s)
E) Sn²⁺(aq) and Al³⁺(aq)

Question 35

Use the following standard reduction potentials to determine which species is the strongest oxidizing agent.
Fe²⁺(aq) + 2 e^- ? Fe(s); E° = -0.41 V
Pt²⁺(aq) + 2 e^- ? Pt(s); E° = 1.18 V
Cr₂O₇^2-(aq) + 14 H⁺(aq) + 6 e^- ? 2 Cr³⁺(aq) + 7 H₂O( $\ell$ ); E° = 1.33 V

A) Fe
B) Pt
C) Cr³⁺
D) Fe²⁺
E) Cr₂O₇^2-

Question 36

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) Al³⁺
B) H⁺
C) Pb²⁺
D) F^-
E) K

Question 37

Calculate $E _ { \text {cell } } ^ { \circ }$ 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) -0.504 V
B) -0.062 V
C) +0.504 V
D) +1.038 V
E) +1.604 V

Question 38

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

A) Li(s)
B) MnO₄^-(aq)
C) H₂(g) and Cl^-(aq)
D) Li(s) and MnO₄^-(aq)
E) Cl^-(aq)

Question 39

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

A) one joule per second
B) one coulomb per joule
C) one joule per coulomb
D) one coulomb per second
E) one calorie per second

Question 40

Calculate E°_cell for the cell for the reaction 2 Ga(s) + 3 Sn⁴⁺(aq) → 3 Sn²⁺(aq) +2 Ga³⁺(aq). The standard reduction potentials are as follows:
Ga³⁺(aq) + 3 e− → Ga(s)
E° = -0.55 V
Sn⁴⁺(aq) + 2 e− → Sn²⁺(aq)
E° = 0.15V
​

A) 0.70 V
B) 0.40 V
C) 0.33 V
D) -0.40 V
E) −0.70 V

Question 41

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) Switching from a platinum to a graphite anode
B) Increasing the size of the anode
C) Decreasing the concentration of Cu²⁺
D) Increasing the concentration of Sn⁴⁺
E) Decreasing the temperature of the cell

Question 42

Which of the following equations represents the Nernst equation?

A) $E = E ^ { \circ } - \left( \frac { R T } { n F } \right) \ln Q$
B) $E = E ^ { \circ } + \log \left( \frac { R T } { n F } \right)$
C) $E = E ^ { \circ } - \left( \frac { R T } { n F } \right) \log Q$
D) $E ^ { \circ } = E - \left( \frac { R T } { n F } \right) \ln Q$
E) $E = E ^ { \circ } - \left( \frac { n F } { R T } \right) \ln Q$

Question 43

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? $$2 \mathrm { MnO } _ { 4 } ^ { - } ( \mathrm { aq } ) + 5 \mathrm { H } _ { 2 } \mathrm { SO } _ { 3 } ( \mathrm { aq } ) \rightarrow 2 \mathrm { Mn } ^ { 2 + } ( \mathrm { aq } ) + 5 \mathrm { SO } _ { 4 } ^ { 2 - } ( \mathrm { aq } ) + 4 \mathrm { H } ^ { + } ( \mathrm { aq } ) + 3 \mathrm { H } _ { 2 } \mathrm { O } ( \mathrm { l } )$$

A) 8
B) 10
C) 5
D) 2
E) 6

Question 44

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) -1.665 V
B) -1.534 V
C) -1.439 V
D) -0.008 V
E) +0.008 V

Question 45

The following has a potential of 0.34 V. $\mathrm { Cu } ^ { 2 + } ( \mathrm { aq } ) + \mathrm { H } _ { 2 } ( \mathrm {~g} ) \rightarrow 2 \mathrm { H } ^ { + } ( \mathrm { aq } ) + \mathrm { Cu } ( \mathrm { s } )$ 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 $\mathrm { Cu } ^ { 2 + } ( \mathrm { aq } ) + 2 e ^ { - } \rightarrow \mathrm { Cu } ( \mathrm { s } )$ is _____.

A) 0.17 V
B) -0.17 V
C) 0.34 V
D) -0.34 V
E) None of these

Question 46

Calculate E_cell 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) -1.034 V
B) -0.590 V
C) -0.508 V
D) -0.555 V
E) +1.034 V

Question 47

Calculate E_cell 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) -0.19 V
B) +0.08 V
C) +0.11 V
D) +0.19 V
E) +0.22 V

Question 48

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) The volume of the Cu²⁺ solution was larger than the volume of the Ag⁺ solution.
B) The volume of the Ag⁺ solution was larger than the volume of the Cu²⁺ solution.
C) The Cu²⁺ concentration was larger than the Ag⁺ concentration.
D) The Ag electrode was twice as large as the Cu electrode.
E) The Ag⁺ concentration was larger than the Cu²⁺ concentration.

Question 49

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

A) Δ_rG° < 0; E°_cell > 0
B) Δ_rG° > 0; E°_cell < 0
C) Δ_rG° < 0; E°_cell < 0
D) Δ_rG° > 0; E°_cell > 0
E) Δ_rG° > 0; E°_cell = 0

Question 50

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) 0.21 M
B) 1.0 M.
C) 0.045 M
D) 1.0 M..
E) 1.0 M

Question 51

A voltaic cell or galvanic cell converts chemical energy to electrical energy. $E _ { \text {cell } } ^ { \circ }$ for the given galvanic cell is -1.80 V. Fe²⁺(aq) + 2 Cl^-(aq) ? Fe(s) + Cl₂(g)
Calculate the value of ?_rG° for the reaction.

A) -174 kJ
B) 86.8 kJ
C) 107 kJ
D) 174 kJ
E) 347 kJ

Question 52

One Faraday is defined as the:

A) charge on a single electron.
B) quantity of electric charge carried by one mole of electrons.
C) voltage required to reduce one mole of reactant.
D) number of moles of electrons required to reduce one mole of a reactant.
E) charge passed by one ampere of current in one second.

Question 53

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) 1.9 × 10^-19 M
B) 5.5 × 10^-10 M
C) 0.018 M
D) 1.03 M
E) 1.8 × 10⁹ M

Question 54

Calculate Δ_rG° 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) -165 kJ/mol⋅rxn
B) -135 kJ/mol⋅rxn
C) -34.9 kJ/mol⋅rxn
D) +17.5 kJ/mol⋅rxn
E) +135 kJ/mol⋅rxn

Question 55

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) 191 kJ
B) 63.7 kJ
C) -504 kJ
D) -191 kJ
E) 1060 kJ

Question 56

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) The standard cell potential is -3.63 V.
B) The standard cell potential is -2.11 V.
C) The standard cell potential is -2.11 V..
D) The standard cell potential is -3.63 V..
E) The standard cell potential is 2.11 V.

Question 57

If the $E _ { \text {cell } } ^ { \circ }$ = -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) 1.77
B) 3.06
C) 6.11
D) 7.89
E) 12.23

Question 58

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. ​
Ag(s) | AgCl(s) | Cl−(aq, 1.0 M) || H⁺(aq) | H₂(g, 1.0 atm) | Pt(s)
​

A) 3.53
B) 11.0
C) 4.03
D) 7.06
E) 3.47

Question 59

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?
$\mathrm { Zn } ^ { 2 + } ( \mathrm { aq } ) + 2 \mathrm { e } ^ { - }$ ? $\mathrm { Zn } ( \mathrm { s } ) ; E ^ { \circ } = - 0.76 \mathrm {~V}$ $\mathrm { Ag } ^ { + } ( \mathrm { aq } ) + \mathrm { e } ^ { - }$ ? $\mathrm { Ag } ( \mathrm { s } ) ; E ^ { \circ } = 0.80 \mathrm {~V}$

A) 8.66 × 10^-3
B) 6.82 × 10^-3
C) 115
D) 1.25 × 10^-2
E) 147

Question 60

Calculate E_cell 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) 0.456 V
B) 0.282 V
C) 0.460 V
D) 0.485 V
E) 0.452 V

Question 61

Which of the following are the expected products when an aqueous solution of lithium sulfate is electrolyzed? $$\begin{array} { l l } \text { Reduction Half-Reaction } & \mathrm { E } ^ { \circ } ( \mathrm { V } ) \\\mathrm { Li } ^ { + } ( \mathrm { aq } ) + \mathrm { e } ^ { - } \rightarrow \mathrm { Li } ( \mathrm { s } ) & - 3.04 \\2 \mathrm { H } _ { 2 } \mathrm { O } ( \ell ) + 2 \mathrm { e } ^ { - } \rightarrow \mathrm { H } _ { 2 } ( \mathrm {~g} ) + 2 \mathrm { OH } ^ { - } ( \mathrm { aq } ) & - 0.83 \\2 \mathrm { H } ^ { + } ( \mathrm { aq } ) + 2 \mathrm { e } ^ { - } \rightarrow \mathrm { H } _ { 2 } ( \mathrm {~g} ) & 0.00 \\\mathrm { O } _ { 2 } ( \mathrm {~g} ) + 4 \mathrm { H } ^ { + } ( \mathrm { aq } ) + 4 \mathrm { e } ^ { - } \rightarrow 2 \mathrm { H } _ { 2 } \mathrm { O } ( \ell ) & 1.23 \\\mathrm {~S} _ { 2 } \mathrm { O } _ { 8 } { } ^ { 2 - } ( \mathrm { aq } ) + 2 \mathrm { e } ^ { - } \rightarrow 2 \mathrm { SO } _ { 4 } { } ^ { 2 - } ( \mathrm { aq } ) & 2.01\end{array}$$

A) Li(s) and H₂(g)
B) H₂(g), OH^-(aq), O₂(g), and H⁺(aq)
C) O₂(g), H⁺(aq), and Li(s)
D) H₂(g), OH^-(aq), and Li(s)
E) H₂(g), OH^-(aq), and S₂O₈^2-(aq)

Question 62

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

A) K(s) → K⁺(l) + e^-
B) Br₂(l) + 2 e^- → 2 Br^-(l)
C) 2 Br^-(l) → Br₂(l) + 2 e^-
D) 2 K⁺(l) + 2 e^- → 2 K(l)
E) 2 H₂O(l) + 2 e^- → H₂(g) + 2 OH^-(l)

Question 63

Batteries used in watches contain mercury(II) oxide. As the current flows, mercury(II) oxide is reduced to mercury according to the following reaction: HgO(s) + H₂O( $\ell$ ) + 2 e^- ? Hg( $\ell$ ) + 2 OH^-(aq)
If 2.3 × 10^-5 amperes flows continuously for 1200 days, calculate the mass of mercury, Hg( $\ell$ ), produced.

A) 2.5 g
B) 5.0 g
C) 9.9 g
D) 13 g
E) 15 g

Question 64

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) 4.0 × 10^-5
B) 2.5 × 10⁴
C) 1.0 × 10⁵
D) 1.2 × 10⁵
E) 1.3 × 10⁵

Question 65

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

A) 5.99 × 10^-4 mol
B) 2.16 mol
C) 57.8 mol
D) 3.35 mol
E) 9.33 × 10³ mol

Question 66

If ?_rG° for the following reaction is -22.2 kJ/mol-rxn, calculate $E _ { \text {cell } } ^ { \circ }$ for the following reaction: Cu²⁺(aq) + 2 Ag(s) + 2 Cl^-(aq) ? Cu(s) + 2 AgCl(s)

A) -0.460 V
B) -0.115 V
C) +0.115 V
D) +0.230 V
E) +0.559 V

Question 67

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.

Question 68

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

Question 69

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

A) 3 × 10^-58
B) 6 × 10⁵
C) 3 × 10¹¹
D) 6 × 10²⁸
E) 3 × 10⁵⁷

Question 70

The value of E°_cell is $0.59 \mathrm {~V}$ 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) -1.18 V
B) -0.30 V
C) 0.59 V
D) 0.30 V
E) -0.59 V

Question 71

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) 0.356 g
B) 21.3 g
C) 192.1 g
D) 0.187 g
E) 32.0 g

Question 72

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) + SO₄^2-(aq)
E° = -0.355 V
Calculate the K_sp for lead(II)sulfate (PbSO₄) at 25 °C.

A) 3.4 × 10^-28
B) 1.8 × 10^-8
C) 5.6 × 10^-5
D) 5.6 × 10⁷
E) 2.9 × 10³⁷

Question 73

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.

Question 74

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) 9.2 × 10^-3 g
B) 3.3 × 10¹ g
C) 9.9 × 10¹ g
D) 1.0 × 10² g
E) 3.0 × 10² g

Question 75

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.

Question 76

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) 0.014
B) 1.7
C) 0.4
D) 1.0
E) 3

Question 77

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

A) 4.1 × 10² C
B) 6.0 × 10³ C
C) 1.2 × 10⁴ C
D) 2.9 × 10⁵ C
E) 3.1 × 10⁶ C

Question 78

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

Question 79

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)
K_f = 2.3 × 10²⁵

A) -1.28 V
B) -0.50 V
C) +1.00 V
D) +1.28 V
E) +3.85 V

Question 80

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) 0.0522 mol
B) 3.13 mol
C) 0.37 mol
D) 0.22 mol
E) 6.27 mol