Deck 18: Electrochemistry

Question 1

What is the oxidation state of vanadium in the VO²⁺ ion?

A) +2
B) +3
C) +4
D) +5
E) none of these

Answer 1

+4

Question 2

The oxidation number of Cl in HClO₃ is:

A) - 1
B) +6
C) +5
D) - 6
E) none of these

Answer 2

+5

Question 3

What is the oxidation number for the carbon atom in COCl₂?

A) 0
B) - 2
C) +2
D) +4
E) - 4

Answer 3

+4

Question 4

The oxidation number of Mn in MnO₄ ^- is:

A) - 1
B) +4
C) +5
D) +7
E) none of these

Question 5

In the peroxydisulfate ion, S₂O₈² - , which has the Lewis structure shown below, what is the oxidation state of the sulfur?

A) - 1
B) - 2
C) +6
D) +7
E) none of these

Question 6

A compound has the empirical formula Na₂O₂. What is the oxidation state of the oxygen?

A) - 1
B) - 2
C) +1
D) +2
E) none of these

Question 7

The oxidation number of Cl in HOCl is:

A) +1
B) +6
C) +3
D) - 1
E) none of these

Question 8

The oxidation state of Cr in Cr₂O₇^{2 -} is:

A) +12
B) +6
C) +7
D) +4
E) none of these

Question 9

What is the oxidation number of the chromium atom in the compound, BaCr₂O₇?

A) 0
B) +2
C) +6
D) +7
E) +12

Question 10

The "super-ion battery" contains K₂FeO₄ as a replacement for MnO₂ in alkaline dry batteries. What is the charge of the iron atom in the compound K₂FeO₄?

A) +2
B) +4
C) +6
D) 0
E) - 4

Question 11

The oxidation state of S in SO₂ is:

A) +2
B) +4
C) - 2
D) - 4
E) none of these

Question 12

What is the oxidation number of the Cr in H₂Cr₂O₇?

A) +5
B) +3
C) +6
D) +4
E) none of these

Question 13

In the azide ion, which has the Lewis structure shown below, the oxidation state of the central N atom is:

A) +1
B) +1/3
C) - 1/3
D) - 1
E) none of these

Question 14

What is the oxidation number of the manganese atom in the formula for the compound KMnO₄?

A) - 1
B) +1
C) +3
D) +5
E) +7

Question 15

The oxidation state of sulfur in SO₃ is:

A) - 3
B) 0
C) +3
D) +6
E) none of these

Question 16

What is the oxidation number of the carbon atom in the compound CO?

A) - 4
B) - 2
C) 0
D) +2
E) +4

Question 17

In which of the following compounds is the oxidation number of the nitrogen atom equal to +5?

A) NH₃
B) N₂O₄
C) NO
D) HNO₃
E) NO₂

Question 18

The oxidation state of chlorine in ClO₄ ^- is:

A) - 1
B) +4
C) +5
D) +7
E) none of these

Question 19

What is the oxidation number of the chlorine in the compound, Ba(ClO₂)₂?

A) 0
B) - 1
C) - 2
D) +3
E) +6

Question 20

The oxidation state of oxygen in O₂F₂ is:

A) - 1
B) - 2
C) +2
D) +1
E) none of these

Question 21

In the properly balanced half-reaction (acid solution) for the system H₃AsO₃→H₂AsO₄ ^- , what else appears on the right side besides H₂AsO₄ ^- ?

A) 2 H⁺ + 2 e ^-
B) 3 H⁺ + 2 e ^-
C) 2 H₂O + 2 e ^-
D) 2 H⁺ + 3 e ^-
E) H⁺

Question 22

Start with the skeleton half-reaction CrO₂ ^- →CrO₄^{2 -} . When balanced in basic solution, what other species appear on the right side of the equation, in addition to CrO₄^{2 -} ?

A) 2 H₂O + 3 e ^-
B) 4 H⁺ + 3 e ^-
C) 2 H₂O
D) 4 OH ^-
E) none of these

Question 23

After balancing the following reaction under acidic conditions , what is the coefficient for the species, BiO₃^{1 -} ?
Mn²⁺ (aq) + BiO₃^{1 -} (aq)→Bi³⁺ (aq) + MnO₄^{1 -} (aq) [Acidic conditions]

A) 1
B) 2
C) 3
D) 5
E) 6

Question 24

What is the oxidizing agent in the following reaction?
H₂O + 2 MnO₄^{1 -} (aq) + I ^- (aq)→2 MnO₂ (s) + IO₃^{1 -} (aq) + 2 OH ^- (aq)

A) H₂O
B) MnO₄^{1 -}
C) I ^-
D) MnO₂
E) IO₃^{1 -}

Question 25

In the redox reaction:
3 S^{2 -} + 2 MnO₄ ^- + 8 H₂O→3 S + 2 MnO₂ + 4 H₂O + 8 OH ^- the S^{2 -} changes oxidation state to give the element S. Which statement below is true?

A) S^{2 -} has been oxidized.
B) S^{2 -} has been reduced.
C) S^{2 -} is an oxidizing agent.
D) S^{2 -} gains electrons.
E) more than one of these

Question 26

The redox reaction (unbalanced), Cl₂→ClO₃ ^- + Cl ^- , occurs in alkaline solution. The number of electrons transferred in the balanced equation is:

A) 2
B) 4
C) 6
D) 8
E) 5

Question 27

After balancing the following reaction under basic conditions , how many mole equivalents of water are required and on which side of the reaction do they appear?
CrO₄^{2 -} (aq) + Cu (s)→Cr(OH)₃ (s) + Cu(OH)₂ (s) [Basic conditions]

A) 2 moles of H₂O on the reactant side
B) 2 moles of H₂O on the product side
C) 4 moles of H₂O on the product side
D) 4 moles of H₂O on the reactant side
E) 8 moles of H₂O on the reactant side

Question 28

After balancing the following reaction under acidic conditions , how many mole equivalents of water are required and on which side of the reaction do they appear?
MnO₄^{1 -} (aq) + Cl^{1 -} (aq)→Mn²⁺ (aq) + Cl₂ (g) [Acidic conditions]

A) 2 moles of H₂O on the reactant side
B) 2 moles of H₂O on the product side
C) 4 moles of H₂O on the product side
D) 8 moles of H₂O on the product side
E) 10 moles of H₂O on the reactant side

Question 29

In the oxidation-reduction reaction shown below, the number of electrons transferred is:
H₂O + 3 ClO ^- (aq)→ClO₂ ^- (aq) + Cl₂ (aq) + 2 OH ^- (aq)

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

Question 30

After balancing the following reaction under acidic conditions , what is the coefficient for the species, Cl^{1 -} ?
MnO₄^{1 -} (aq) + Cl^{1 -} (aq)→Mn²⁺ (aq) + Cl₂ (g) [Acidic conditions]

A) 1
B) 2
C) 5
D) 7
E) 10

Question 31

After balancing the following reaction under basic conditions , what is the coefficient for the copper?
CrO₄^{2 -} (aq) + Cu (s)→Cr(OH)₃ (s) + Cu(OH)₂ (s) [Basic conditions]

A) 1
B) 2
C) 3
D) 6
E) 9

Question 32

Which equation listed below is correct after balancing the following unbalanced equation under basic conditions ?
MnO₄^{1 -} (aq) + Br^{1 -} (aq)→MnO₂ (s) + BrO₃^{1 -} (aq) [Basic conditions]

A) MnO₄^{1 -} (aq) + Br^{1 -} (aq) + 2 OH ^- (aq)→ MnO₂ (s) + BrO₃^{1 -} (aq) + H₂O
B) MnO₄^{1 -} (aq) + 2 Br^{1 -} (aq) + 8 OH ^- (aq)→ MnO₂ (s) + 2 BrO₃^{1 -} (aq) + 4 H₂O
C) 2 MnO₄^{1 -} (aq) + Br^{1 -} (aq) + H₂O→ 2 MnO₂ (s) + BrO₃^{1 -} (aq) + 2 OH ^- (aq)
D) 2 H⁺ (aq) + 2 MnO₄^{1 -} (aq) + Br^{1 -} (aq)→ 2 MnO₂ (s) + BrO₃^{1 -} (aq) + H₂O
E) 2 MnO₄^{1 -} (aq) + 2 Br^{1 -} (aq) + 4 OH ^- (aq)→ 2 MnO₂ (s) + 2 BrO₃^{1 -} (aq) + 2 H₂O

Question 33

After balancing the following reaction under basic conditions , how many electrons are transferred?
MnO₄^{1 -} (aq) + Br^{1 -} (aq)→MnO₂ (s) + BrO₃^{1 -} (aq) [Basic conditions]

A) 1 electron
B) 2 electrons
C) 3 electrons
D) 6 electrons
E) 9 electrons

Question 34

What species becomes oxidized and what species behaves as the reducing agent in the following oxidation-reduction reaction?
2 H₂ O ( ) + Al (s) + MnO₄ 1 - (aq) Al(OH) 4 1 - (aq) + MnO₂ (s)

A) Al becomes oxidized and Al behaves as the reducing agent.
B) Al becomes oxidized and MnO₄^{1 -} behaves as the reducing agent.
C) MnO₄^{1 -} becomes oxidized and MnO₄^{1 -} behaves as the reducing agent.
D) MnO₄^{1 -} becomes oxidized and Al behaves as the reducing agent.
E) MnO₄^{1 -} becomes oxidized and H₂O behaves as the reducing agent.

Question 35

After balancing the following reaction under acidic conditions , how many electrons are transferred?
Mn²⁺ (aq) + BiO₃^{1 -} (aq)→Bi³⁺ (aq) + MnO₄^{1 -} (aq) [Acidic conditions]

A) 1 electron
B) 2 electrons
C) 5 electrons
D) 7 electrons
E) 10 electrons

Question 36

In the following balanced redox reaction:
14 HCl + K₂Cr₂O₇ + 6 FeCl₂→2 CrCl₃ + 6 FeCl₃ + 2 KCl + 7 H ₂O

A) K₂Cr₂O₇ is oxidized.
B) FeCl₂ is a reducing agent.
C) HCl is an oxidizing agent.
D) HCl is oxidized.
E) none of these.

Question 37

Start with the skeleton half-reaction NO₃ ^- →NO₂. When balanced in acid solution, what other species appear on the left side of the equation, in addition to NO₃ ^-?

A) H₂O + 2 e ^-
B) 2 H⁺ + e ^-
C) H⁺ + 2 e ^-
D) 2 H⁺
E) none of these

Question 38

Given the skeleton half-reaction:
Na₂C₂O₄→CO₂ + Na⁺ When the half-reaction is properly balanced we find that the half-reaction represents:

A) an oxidation.
B) a reduction.
C) neither

Question 39

Start with the skeleton half-reaction NO₂ ^- →NO₃ ^- . When balanced in basic solution, what other species appear on the right side of the equation, in addition to NO₃ ^- ?

A) 2 H⁺ + 2 e ^-
B) 2 OH ^-
C) H₂O + 2 e ^-
D) H₂O
E) none of these

Question 40

In the oxidation-reduction equation (balanced):
H₂O + 3 ClO ^- (aq)→ClO₂ ^- (aq) + Cl₂ (aq) + 2 OH ^- (aq)

A) ClO ^- is reduced.
B) ClO ^- is oxidized.
C) ClO ^- is an oxidizing agent.
D) ClO ^- is a reducing agent.
E) choices a-d are all correct statements.

Question 41

Which of the following voltaic cell reactions would not require a salt bridge?

A) Ce⁴⁺ + Fe²⁺→ Ce³⁺ + Fe³⁺
B) Cu (s) + 2 Ag⁺→ Cu²⁺ + 2 Ag (s)
C) H₂ (g) + 2 AgCl (s)→ 2 H⁺ + 2 Cl ^-
D) 2 Cu²⁺ + 4 I ^- → CuI (s) + I₂ (s)
E) all of these cells require a salt bridge

Question 42

Exhibit 18-1 Consider the figure of a generic voltaic cell below to answer the following question(s).
Refer to Exhibit 18-1. If electrons are flowing in the direction from half-cell D to half-cell B, which component in this voltaic cell represents the electrode where oxidation occurs ?

A) A
B) B
C) C
D) D
E) E

Question 43

A sample solution contains Sn²⁺ ions and is titrated with a 0.0500 M solution of Ce⁴⁺, consuming 35.44 mL of the Ce⁴⁺ solution. The products of the redox reaction are Sn⁴⁺ and Ce³⁺. What mass of Sn²⁺ was present in the original solution?

A) 8.86×10 ^{- 4} g
B) 0.105 g
C) 0.210 g
D) 0.420 g
E) none of these

Question 44

A sample containing Fe₂O₃ is dissolved and the Fe³⁺ is reduced to Fe²⁺, which is titrated with standard 0.0200 M KMnO₄. The skeleton equation is:
Fe²⁺ + MnO₄ ^- →Fe³⁺ + Mn²⁺ How many grams of iron (molar mass = 55.85 g/mol) are in the sample, if 25.0 mL of KMnO₄ are required in the titration?

A) 0.140 g
B) 0.0279 g
C) 5.58×10 ^{- 3} g
D) 140 g
E) need more information

Question 45

Exhibit 18-1 Consider the figure of a generic voltaic cell below to answer the following question(s).
Refer to Exhibit 18-1. If electrons are flowing in the direction from half-cell D to half-cell B, what is the purpose of component C in the voltaic cell above?

A) It is a salt solution that provides cations that can migrate to compartment B and anions that migrate to compartment D in an effort to balance the charge as electricity flows.
B) It is a salt solution that provides anions that can migrate to compartment B and cations that migrate to compartment D in an effort to balance the charge as electricity flows.
C) It allows mixing of solutions in compartments B and D.
D) Its purpose is to hold the two cells together.
E) Electricity flows through this region to complete the circuit as electricity flows.

Question 46

Which of the following half-reactions could occur at the negative electrode of a voltaic cell?

A) Cu²⁺ + 2 e ^- → Cu
B) Fe³⁺ + e ^- → Fe²⁺
C) Zn→ Zn²⁺ + 2 e ^-
D) Cu→ Cu²⁺ + 2 e ^-
E) both answers c and d

Question 47

In a voltaic cell:

A) oxidation occurs at the positive electrode.
B) electrons flow through the external circuit from the negative to the positive electrode.
C) the charge is carried through the solution by electrons and protons.
D) electrical energy is consumed to cause a chemical change.
E) none of these.

Question 48

After balancing the following reaction under acidic conditions , how many mole equivalents of water are required and on which side of the reaction do they appear?
CrO₄^{2 -} (aq) + N₂O (aq)→Cr³⁺ (aq) + NO (g) [Acidic conditions]

A) 2 moles of H₂O on the reactant side
B) 2 moles of H₂O on the product side
C) 5 moles of H₂O on the product side
D) 5 moles of H₂O on the reactant side
E) 10 moles of H₂O on the reactant side

Question 49

Exhibit 18-1 Consider the figure of a generic voltaic cell below to answer the following question(s).
Refer to Exhibit 18-1. If component A is the positive electrode and component E is the negative electrode, which statement is true?

A) Electrons are flowing from left to right (A→ E) in this figure. Electrode E is "swelling" as metal ions plate onto its surface.
B) Electrons are flowing from left to right (A→ E) in this figure. Electrode E is corroding as metal atoms dissolve into solution D.
C) Electrons are flowing from right to left (E→ A) in this figure. Electrode E is "swelling" as metal ions plate onto its surface.
D) Electrons are flowing from right to left (E→ A) in this figure. Electrode E is corroding as metal atoms dissolve into solution D.
E) Electrons are not flowing in this voltaic cell unless it is provided by an outside source.

Question 50

After balancing the following reaction under basic conditions , what is the coefficient for the sulfite species, SO₃^{2 -} ?
SO₃^{2 -} (aq) + Cl₂ (g)→SO₄^{2 -} (aq) + Cl^{1 -} (aq) [Basic conditions]

A) 1
B) 2
C) 3
D) 4
E) 6

Question 51

Consider a voltaic cell that operates from the following redox reaction:
Al (s) + Cr³⁺ (aq)→Al³⁺ (aq) + Cr (s) What half-reaction operates at the positive electrode of this cell?

A) Al (s)→ Al³⁺ (aq) + 3 e ^-
B) Al³⁺ (aq) + 3 e ^- → Al (s)
C) Cr (s)→ Cr³⁺ (aq) + 3 e ^-
D) Cr³⁺ (aq) + 3 e ^- → Cr (s)
E) Al³⁺ (aq) + 3 e ^- → Cr (s)

Question 52

After balancing the following reaction under acidic conditions , what is the coefficient for N₂O?
CrO₄^{2 -} (aq) + N₂O (aq)→Cr³⁺ (aq) + NO (g) [Acidic conditions]

A) 1
B) 2
C) 3
D) 4
E) 6

Question 53

A 30.0 mL sample of solution containing Fe²⁺ requires 25.0 mL of 0.0200 M KMnO₄ solution to react completely. The products of the reaction are Fe³⁺ and Mn²⁺. What is the concentration of Fe²⁺ in the original solution?

A) 3.33×10 ^{- 3} M
B) 1.67×10 ^{- 2} M
C) 8.33×10 ^{- 2} M
D) 0.500 M
E) none of these

Question 54

After balancing the following reaction under basic conditions , how many mole equivalents of hydroxide are required and on which side of the reaction do they appear?
SO₃^{2 -} (aq) + Cl₂ (g)→SO₄^{2 -} (aq) + Cl^{1 -} (aq) [Basic conditions]

A) 2 moles of OH ^- on the reactant side
B) 2 moles of OH ^- on the product side
C) 5 moles of OH ^- on the product side
D) 5 moles of OH ^- on the reactant side
E) 10 moles of OH ^- on the reactant side

Question 55

With respect to any voltaic cell, at what electrode does reduction occur and what is the sign convention given to this electrode?

A) anode; "+" terminal
B) anode; " - " terminal
C) cathode; "+" terminal
D) cathode; " - " terminal
E) None of these

Question 56

Which of the following processes could occur at the positive electrode of a voltaic cell?

A) Cu²⁺ + 2 e ^- → Cu
B) Fe³⁺ + e ^- → Fe²⁺
C) Zn→ Zn²⁺ + 2 e ^-
D) Cu→ Cu²⁺ + 2 e ^-
E) both answers a and b

Question 57

Consider a voltaic cell that operates from the following redox reaction:
Mn (s) + Ag¹⁺ (aq)→Mn²⁺ (aq) + Ag (s) What half-reaction operates at the negative electrode of this cell?

A) Mn (s)→ Mn²⁺ (aq) + 2 e ^-
B) Ag¹⁺ (aq) + 1 e ^- → Ag (s)
C) Ag (s)→ Ag¹⁺ (aq) + 1 e ^-
D) Mn²⁺ (aq) + 2 e ^- → Mn (s)
E) Mn²⁺ (aq) + 2 e ^- → Ag (s)

Question 58

A voltaic cell consists of two half-cells:
Zinc metal immersed in a 1 M solution of ZnCl₂ and copper immersed in a 1M solution of CuSO₄. The copper electrode is positive. What is the spontaneous chemical reaction that occurs in this cell?

A) Cu (s) + Zn²⁺→ Zn (s) + Cu²⁺
B) Zn (s) + Cu²⁺→ Zn²⁺ + Cu (s)
C) Zn²⁺ + Cu²⁺→ Zn (s) + Cu (s)
D) No chemical reaction occurs.
E) none of these

Question 59

Under standard conditions, the spontaneous reaction in a voltaic cell i S₂U³⁺ + Cd²⁺→2 U⁴⁺ + Cd (s). Consider the three statements below and choose the correct answer.
I. The cadmium is the positive electrode in the cell.
II. A salt bridge is necessary in this cell.
III. The U³⁺ is oxidized in the cell.

A) only I is true
B) only II is true
C) only III is true
D) I, II, and III are all true
E) only 2 of the three statements are true

Question 60

In a voltaic cell, the spontaneous reaction that occurs is Cr (s) + Cu²⁺→Cu (s) + Cr²⁺. Consider the following three statements and choose the correct answer.
I. The chromium metal is the negative electrode.
II. A salt bridge is unnecessary in this voltaic cell.
III. Copper (II) ions are reduced.

A) only I is true
B) only III is true
C) II and III are true, I is false
D) I and III are true, II is false
E) I, II, and III are all true

Question 61

Exhibit 18-2 Consider a voltaic cell that is constructed from a strip of Ag dipped in an AgNO₃ solution and a Fe (s) strip dipped in a solution of FeCl₂ to answer the following question(s). An external circuit and a salt bridge connect these two electrodes.
Refer to Exhibit 18-2. Which electrode is the negative electrode and what is the standard potential E ° _cell for this voltaic cell?

A) The Fe²⁺/Fe couple is the negative electrode and E ° _cell = 1.24 V.
B) The Fe²⁺/Fe couple is the negative electrode and E ° _cell = 0.36 V.
C) The Fe²⁺/Fe couple is the negative electrode and E ° _cell = - 1.24 V.
D) The Ag⁺/Ag couple is the negative electrode and E ° _cell = 1.24 V.
E) The Ag⁺/Ag couple is the negative electrode and E ° _cell = 0.36 V.

Question 62

Given:
Cu (s) + 2 Ag⁺→2 Ag (s) + Cu²⁺ E ° = +0.46 V Cu²⁺ + H₂ (g)→Cu (s) + 2 H⁺ E ° = +0.34 V Find the standard potential for the cell reaction for:
2 Ag⁺ + H₂ (g)→2 Ag + 2 H⁺

A) +0.80 V
B) +0.40 V
C) +0.12 V
D) - 0.12 V
E) none of these

Question 63

Exhibit 18-3 Use the standard reduction potentials below to answer the following question(s).
Ce⁴⁺(aq) + e ^- →Ce³⁺(aq) E ° = 1.61 V
Fe³⁺(aq) + e ^- →Fe²⁺(aq) E ° = 0.77 V
I₂(s) + 2 e ^- →2 I ^- (aq) E ° = 0.54 V
2 H⁺(aq) + 2 e ^- →H₂(g) E ° = 0.000 V
Cd²⁺(aq) + 2 e ^- →Cd(s) E ° = - 0.40 V
U⁴⁺(aq) + e ^- →U³⁺(aq) E ° = - 0.61 V
CdCO₃(s) + 2 e ^- →Cd(s) + CO₃^{2 -} (aq) E ° = - 0.74 V
Zn²⁺(aq) + 2 e ^- →Zn(s) E ° = - 0.76 V
U³⁺(aq) + 3 e ^- →U(s) E ° = - 1.80 V
Mg²⁺(aq) + 2 e ^- →Mg(s) E ° = - 2.37 V
Refer to Exhibit 18-3. Find the standard potential for the reaction:
2 U⁴⁺ + 2 I ^- →2 U³⁺ + I₂ (s)

A) +0.58 V
B) - 0.04 V
C) - 0.07 V
D) - 1.15 V
E) none of these

Question 64

Consider a voltaic cell that operates from the following redox reaction:
Mn (s) + Ag¹⁺ (aq)→Mn²⁺ (aq) + Ag (s) What is the value of E ° _cell if E ° _red(Ag¹⁺/Ag) = 0.80 V and E ° _red(Mn²⁺/Mn) = - 1.18 V?

A) E ° _cell = - 1.98 V
B) E ° _cell = - 0.94 V
C) E ° _cell = - 0.38 V
D) E ° _cell = 0.38 V
E) E ° _cell = 1.98 V

Question 65

Given:
Zn (s) + Sn²⁺→Sn (s) + Zn²⁺ with E ° = +0.62 V What is the equilibrium constant for this reaction at 298 K?

A) 21
B) 1×10²¹
C) 5×10²⁰
D) 3×10¹⁰
E) 4×10 ^{- 31}

Question 66

Consider the following redox reaction:
2 Li⁺ (aq) + Fe (s)→Fe²⁺ (aq) + 2 Li (s) Which statement below is true regarding (1) the spontaneity of this reaction and (2) the value of E ° _cell?
E ° _red(Li¹⁺/Li) = - 3.05V and E ° _red(Fe²⁺/Fe) = - 0.44 V

A) This reaction is spontaneous as written and E ° _cell = - 2.61 V.
B) This reaction is non-spontaneous as written and E ° _cell = - 2.61 V.
C) This reaction is spontaneous as written and E ° _cell = 2.61 V.
D) This reaction is non-spontaneous as written and E ° _cell = 2.61 V.
E) This reaction is non-spontaneous as written and E ° _cell = - 3.49 V.

Question 67

Exhibit 18-3 Use the standard reduction potentials below to answer the following question(s).
Ce⁴⁺(aq) + e ^- →Ce³⁺(aq) E ° = 1.61 V
Fe³⁺(aq) + e ^- →Fe²⁺(aq) E ° = 0.77 V
I₂(s) + 2 e ^- →2 I ^- (aq) E ° = 0.54 V
2 H⁺(aq) + 2 e ^- →H₂(g) E ° = 0.000 V
Cd²⁺(aq) + 2 e ^- →Cd(s) E ° = - 0.40 V
U⁴⁺(aq) + e ^- →U³⁺(aq) E ° = - 0.61 V
CdCO₃(s) + 2 e ^- →Cd(s) + CO₃^{2 -} (aq) E ° = - 0.74 V
Zn²⁺(aq) + 2 e ^- →Zn(s) E ° = - 0.76 V
U³⁺(aq) + 3 e ^- →U(s) E ° = - 1.80 V
Mg²⁺(aq) + 2 e ^- →Mg(s) E ° = - 2.37 V

Refer to Exhibit 18-3. The strongest reducing agent in this series is:

A) Mg²⁺
B) Mg (s)
C) Ce⁴⁺
D) Ce³⁺
E) none of these

Question 68

Exhibit 18-2 Consider a voltaic cell that is constructed from a strip of Ag dipped in an AgNO₃ solution and a Fe (s) strip dipped in a solution of FeCl₂ to answer the following question(s). An external circuit and a salt bridge connect these two electrodes.
Refer to Exhibit 18-2. Which cell reaction ensues spontaneously in this voltaic cell?

A) Fe²⁺ (aq) + 2 Ag (s)→ Fe (s) + 2 Ag⁺ (aq)
B) Fe²⁺ (aq) + 2 Ag⁺ (aq)→ Fe (s) + 2 Ag (s)
C) Fe (s) + 2 Ag (s)→ Fe²⁺ (aq) + 2 Ag⁺ (aq)
D) Fe (s) + 2 Ag⁺ (aq)→ Fe²⁺ (aq) + 2 Ag (s)
E) Fe²⁺ (aq) + Fe (s)→ 2 Ag¹⁺ (aq) + 2 Ag (s)

Question 69

A standard cell with the reaction 2 H⁺ + 2 Cr²⁺→H₂ (g) + 2 Cr³⁺ has a potential of 0.44 V. What is the standard reduction potential for the half-reaction:
Cr³⁺ + e ^- →Cr²⁺

A) +0.44 V
B) +0.22 V
C) - 0.22 V
D) - 0.44 V
E) not enough information

Question 70

Exhibit 18-3 Use the standard reduction potentials below to answer the following question(s).
Ce⁴⁺(aq) + e ^- →Ce³⁺(aq) E ° = 1.61 V
Fe³⁺(aq) + e ^- →Fe²⁺(aq) E ° = 0.77 V
I₂(s) + 2 e ^- →2 I ^- (aq) E ° = 0.54 V
2 H⁺(aq) + 2 e ^- →H₂(g) E ° = 0.000 V
Cd²⁺(aq) + 2 e ^- →Cd(s) E ° = - 0.40 V
U⁴⁺(aq) + e ^- →U³⁺(aq) E ° = - 0.61 V
CdCO₃(s) + 2 e ^- →Cd(s) + CO₃^{2 -} (aq) E ° = - 0.74 V
Zn²⁺(aq) + 2 e ^- →Zn(s) E ° = - 0.76 V
U³⁺(aq) + 3 e ^- →U(s) E ° = - 1.80 V
Mg²⁺(aq) + 2 e ^- →Mg(s) E ° = - 2.37 V
Refer to Exhibit 18-3. Which one of the following reactions proceeds spontaneously to the right when all reactants and products are in their standard states?

A) 2 Fe³⁺ (aq) + 2 I ^- (aq)→ 2 Fe²⁺ (aq) + I₂ (s)
B) Cd (s) + Zn²⁺ (aq)→ Cd²⁺ (aq) + Zn (s)
C) 4 U³⁺ (aq)→ 3 U⁴⁺ (aq) + U (s)
D) 2 U⁴⁺ (aq) + Cd²⁺ (aq)→ 2 U³⁺ (aq) + Cd (s)
E) none of these

Question 71

A voltaic cell is based on a Co²⁺/Co half-cell and an Ag¹⁺/Ag half-cell. Given E ° _red(Co²⁺/Co) = - 0.277 V and E ° _red(Ag¹⁺/Ag) = +0.222 V, which statement below is true regarding which half cell operates at the positive electrode and what is the standard cell potential E ° _cell for this voltaic cell?

A) The Co²⁺/Co half-cell operates at the positive electrode and the standard cell potential E ° _cell is 0.499 V.
B) The Co²⁺/Co half-cell operates at the positive electrode and the standard cell potential E ° _cell is - 0.055 V.
C) The Co²⁺/Co half-cell operates at the positive electrode and the standard cell potential E ° _cell is 0.055 V.
D) The Ag¹⁺/Ag half-cell operates at the positive electrode and the standard cell potential E ° _cell is 0.499 V.
E) The Ag¹⁺/Ag half-cell operates at the positive electrode and the standard cell potential E ° _cell is 0.055 V.

Question 72

The E ° for a particular electrochemical reaction was found to be E ° = +1.086 V. This value of E ° means that under standard conditions this reaction is:

A) nonspontaneous
B) spontaneous
C) at equilibrium
D) exothermic
E) endothermic

Question 73

Given:
Ag⁺¹ (aq) + e ^- ?Ag (s) E ° = 0.800 V Cl₂ (g) + 2 e ^- ?2 Cl ^- (aq) E ° = +1.36 V Zn²⁺ (aq) + 2 e ^- ?Zn (s) E ° = - 0.76 V What is the proper arrangement for the order of increasing strength as a reducing agent ?
Ag (s), Cl ^- (aq) and Zn (s)

A) (weakest reducing agent) Ag (s) - (aq) < Zn (s) (strongest reducing agent)
B) (weakest reducing agent) Cl ^- (aq) < Ag (s) < Zn (s) (strongest reducing agent)
C) (weakest reducing agent) Zn (s) - (aq) < Ag (s) (strongest reducing agent)
D) (weakest reducing agent) Ag (s) - (aq) (strongest reducing agent)
E) (weakest reducing agent) Cl ^- (aq) < Zn (s) < Ag (s) (strongest reducing agent)

Question 74

The E ° for a particular electrochemical reaction was found to be E ° = +1.38 V. This value of E ° means that this reaction is

A) spontaneous and D G ° is negative.
B) nonspontaneous and D G ° is positive.
C) in an equilibrium state and D G ° is zero.
D) exothermic and D H ° is negative.
E) endothermic and D H ° is positive.

Question 75

Exhibit 18-3 Use the standard reduction potentials below to answer the following question(s).
Ce⁴⁺(aq) + e ^- →Ce³⁺(aq) E ° = 1.61 V
Fe³⁺(aq) + e ^- →Fe²⁺(aq) E ° = 0.77 V
I₂(s) + 2 e ^- →2 I ^- (aq) E ° = 0.54 V
2 H⁺(aq) + 2 e ^- →H₂(g) E ° = 0.000 V
Cd²⁺(aq) + 2 e ^- →Cd(s) E ° = - 0.40 V
U⁴⁺(aq) + e ^- →U³⁺(aq) E ° = - 0.61 V
CdCO₃(s) + 2 e ^- →Cd(s) + CO₃^{2 -} (aq) E ° = - 0.74 V
Zn²⁺(aq) + 2 e ^- →Zn(s) E ° = - 0.76 V
U³⁺(aq) + 3 e ^- →U(s) E ° = - 1.80 V
Mg²⁺(aq) + 2 e ^- →Mg(s) E ° = - 2.37 V
Refer to Exhibit 18-3. The strongest oxidizing agent in this list is:

A) Mg²⁺
B) Mg (s)
C) Ce⁴⁺
D) Ce³⁺
E) none of these

Question 76

Under standard conditions the voltaic cell with the reaction H₂ (g) + 2 Fe³⁺→2 Fe²⁺ + 2 H⁺ has a potential of 0.77 V. What is the standard reduction potential for the half-reaction:
Fe³⁺ + e ^- →Fe²⁺

A) +0.77 V
B) +0.38 V
C) - 0.38 V
D) - 0.77 V
E) not enough information

Question 77

Given:
F₂ (g) + 2 e ^- ?2 F ^- E ° = +2.87 V Cr₂O ₇^{2 -} (aq) + 14 H⁺ (aq) + 6 e ^- ?2 Cr³⁺ (aq) + 7 H₂O E ° = 1.33 V Li⁺ (aq) + 1 e ^- (aq)?Li (s) E ° = - 3.05 V What is the proper arrangement for the order of increasing strength as an oxidizing agent ?
F₂ (g), Cr₂O₇^{2 -} (aq) and Li⁺ (aq)

A) (weakest oxidizing agent) F₂ (g) - (aq) < Li⁺ (aq) (strongest)
B) (weakest oxidizing agent) Cr₂O₇^{2 -} (aq) < F₂ (g) < Li⁺ (aq) (strongest)
C) (weakest oxidizing agent) Cr₂O₇^{2 -} (aq) < Li⁺ (aq) < F₂ (g) (strongest)
D) (weakest oxidizing agent) Li⁺ (aq) - (aq) (strongest)
E) (weakest oxidizing agent) Li⁺ (aq) - (aq) < F₂ (g) (strongest)

Question 78

Which of the following is associated with a redox reaction that would proceed spontaneously towards the product side of the equation without having any outside work supplied to the system?
I. D G
II. E _cell > 0
III. Q / K

A) I only
B) II only
C) III only
D) I and II
E) All of these

Question 79

Given:
2 Fe³⁺ + Cu (s)→Cu²⁺ + 2 Fe²⁺ E ° = +0.43 V 2 Ag⁺ + Cu (s)→Cu²⁺ + 2 Ag (s) E ° = +0.46 V What is the standard potential for the cell reaction in the following reaction?
Fe²⁺ + Ag⁺→Ag (s) + Fe³⁺

A) +0.89 V
B) +0.44 V
C) +0.03 V
D) - 0.03 V
E) none of these

Question 80

The E ° for a particular electrochemical reaction was found to be E ° = - 0.86 V. This value of E ° means that under standard conditions this reaction is:

A) nonspontaneous
B) spontaneous
C) at equilibrium
D) exothermic
E) endothermic