Deck 20: Electrochemistry

Question 1

What is the oxidation number of sulfur in the HSO₄^- ion?

A)-2
B)+1
C)+2
D)+4
E)+6

Answer 1

+6

Question 2

Which of the following reactions is a redox reaction? (a)K₂CrO₄ + BaCl₂ → BaCrO₄ + 2KCl
(b)Pb₂²⁺ + 2Br^- → PbBr
(c)Cu + S → CuS

A)(a)only
B)(b)only
C)(c)only
D)(a)and (c)
E)(b)and (c)

Answer 2

(c)only

Question 3

Which element is oxidized in the reaction below? Fe⁺² + H⁺ + Cr₂O₇^-2 → Fe⁺³ + Cr⁺³ + H₂O

A)Fe
B)Cr
C)O
D)H

Answer 3

Fe

Question 4

What is the coefficient of the permanganate ion when the following equation is balanced? MnO₄^- + Br^- → Mn²⁺ + Br₂ (acidic solution)

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

Question 5

Which transformation could take place at the anode of an electrochemical cell?

A)Cr₂O₇^2- → Cr²⁺
B)F₂ to F^-
C)O₂ to H₂O
D)HAsO₂ to As
E)None of the above could take place at the anode.

Question 6

What is the coefficient of the dichromate ion when the following equation is balanced? Fe²⁺ + Cr₂O₇^2- → Fe³⁺ + Cr³⁺ (acidic solution)

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

Question 7

Which element is reduced in the reaction below? Fe⁺² + H⁺ + Cr₂O₇^-2 → Fe⁺³ + Cr⁺³ + H₂O

A)Fe
B)Cr
C)O
D)H

Question 8

Which element is oxidized in the reaction below? I^- + MnO₄^- + H⁺ → I₂ + MnO₂ + H₂O

A)I
B)Mn
C)O
D)H

Question 9

Which element is reduced in the reaction below? Fe(CO)₅ (l)+ 2HI (g)→ Fe(CO)₄I₂ (s)+ CO (g)+ H₂ (g)

A)Fe
B)C
C)O
D)H
E)I

Question 10

Which substance is the oxidizing agent in the following reaction? Fe₂S₃ + 12HNO₃ → 2Fe(NO₃)₃ + 3S + 6NO₂ + 6H₂O

A)HNO₃
B)S
C)NO₂
D)Fe₂S₃
E)H₂O

Question 11

The purpose of the salt bridge in an electrochemical cell is to __________.

A)maintain electrical neutrality in the half-cells via migration of ions.
B)provide a source of ions to react at the anode and cathode.
C)provide oxygen to facilitate oxidation at the anode.
D)provide a means for electrons to travel from the anode to the cathode.
E)provide a means for electrons to travel from the cathode to the anode.

Question 12

Which transformation could take place at the cathode of an electrochemical cell?

A)MnO₂ → MnO₄^-
B)Br₂ → BrO₃^-
C)NO → HNO₂
D)HSO₄^- → H₂SO₃
E)Mn²⁺ → MnO₄^-

Question 13

Which one of the following reactions is a redox reaction?

A)NaOH + HCl → NaCl + H₂O
B)Pb²⁺ + 2Cl^- → PbCl₂
C)AgNO₃ + HCl → HNO₃ + AgCl
D)None of the above is a redox reaction.

Question 14

What is the oxidation number of bromine in the BrO₃^- ion?

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

Question 15

Which element is oxidized in the reaction below? Fe(CO)₅ (l)+ 2HI (g)→ Fe(CO)₄I₂ (s)+ CO (g)+ H₂ (g)

A)Fe
B)C
C)O
D)H
E)I

Question 16

Which element is reduced in the reaction below? I^- + MnO₄^- + H⁺ → I₂ + MnO₂ + H₂O

A)I
B)Mn
C)O
D)H

Question 17

Which substance is the reducing agent in the following reaction? Fe₂S₃ + 12HNO₃ → 2Fe(NO₃)₃ + 3S + 6NO₂ + 6H₂O

A)HNO₃
B)S
C)NO₂
D)Fe₂S₃
E)H₂O

Question 18

What is the oxidation number of nitrogen in the HNO₃?

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

Question 19

What is the coefficient of Fe³⁺ when the following equation is balanced? CN^- + Fe³⁺ → CNO^- + Fe²⁺ (basic solution)

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

Question 20

Which transformation could take place at the anode of an electrochemical cell?

A)NO → NO₃^-
B)CO₂ → Cr₂O₄^2-
C)VO₂⁺ → VO²⁺
D)H₂AsO₄ → H₃AsO₃
E)O₂ → H₂O₂

Question 21

Which of the following reactions will occur spontaneously as written?

A)3Fe²⁺ (aq)+ Cr³⁺ (aq)→ Cr (s)+ 3Fe³⁺ (aq)
B)2Cr³⁺ (aq)+ 3Sn²⁺ (aq)→ 3Sn⁴⁺ (aq)+ 2Cr (s)
C)Sn⁴⁺ (aq)+ Fe²⁺ (s)→ Sn²⁺ (aq)+ Fe (s)
D)Sn²⁺ (aq)+ Fe²⁺ (s)→ Sn⁴⁺ (aq)+ Fe³⁺ (aq)
E)2Cr (s)+ 3Fe²⁺ (s)→ 3Fe (s)+ 2Cr³⁺ (aq)

Question 22

Consider an electrochemical cell based on the reaction: 2H⁺ (aq)+ Sn (s)→ Sn²⁺ (aq)+ H₂ (g)
Which of the following actions would not change the measured cell potential?

A)lowering the pH in the cathode compartment
B)addition of more tin metal to the anode compartment
C)increasing the tin (II)ion concentration in the anode compartment
D)increasing the pressure of hydrogen gas in the cathode compartment
E)Any of the above will change the measured cell potential.

Question 23

What is the cathode in the hydrogen fuel cell?

A)O₂
B)KOH
C)Li
D)H₂
E)Pt

Question 24

In a lead-acid battery, the electrodes are consumed. In this battery,

A)the anode is Pb.
B)the anode is PbSO₄.
C)the anode is PbO₂.
D)the cathode is PbSO₄.
E)the cathode is Pb.

Question 25

One of the differences between a voltaic cell and an electrolytic cell is that in an electrolytic cell __________.

A)an electric current is produced by a chemical reaction
B)electrons flow toward the anode
C)a nonspontaneous reaction is forced to occur
D)O₂ gas is produced at the cathode
E)oxidation occurs at the cathode

Question 26

Which of the following reactions will occur spontaneously as written?

A)Sn⁴⁺ (aq)+ Fe³⁺ (aq)→ Sn²⁺ (aq)+ Fe²⁺ (aq)
B)3Fe (s)+ 2Cr³⁺ (aq)→ 2Cr (s)+ 3Fe²⁺ (aq)
C)Sn⁴⁺ (aq)+ Fe²⁺ (aq)→ Sn²⁺ (aq)+ Fe (s)
D)3Sn⁴⁺ (aq)+ 2Cr (s)→ 2Cr³⁺ (aq)+ 3Sn²⁺ (aq)
E)3Fe²⁺ (aq)→ Fe (s)+ 2Fe³⁺ (aq)

Question 27

__________ is oxidized in the following reaction: Cr₂O₇^2- + 6S₂O₃^2- + 14H⁺ → 2Cr³⁺ + 3S₄O₆^2- + 7H₂O

A)Cr⁶⁺
B)S²⁺
C)H⁺
D)O^2-
E)S₄O₆^2-

Question 28

Which substance is serving as the oxidizing agent in the following reaction? 14H⁺ + Cr₂O₇^2- + 3Ni → 3Ni²⁺ + 2Cr³⁺ + 7H₂O

A)Ni
B)H⁺
C)Cr₂O₇^2-
D)H₂O
E)Ni²⁺

Question 29

Which one of the following types of elements is most likely to be a good oxidizing agent?

A)alkali metals
B)lanthanides
C)alkaline earth elements
D)transition elements
E)halogens

Question 30

What is the cathode in an alkaline battery?

A)MnO₂
B)KOH
C)Zn powder
D)Mn₂O₃
E)Pt

Question 31

Cathodic protection of a metal pipe against corrosion usually entails

A)attaching an active metal to make the pipe the anode in an electrochemical cell.
B)coating the pipe with another metal whose standard reduction potential is less negative than that of the pipe.
C)attaching an active metal to make the pipe the cathode in an electrochemical cell.
D)attaching a dry cell to reduce any metal ions which might be formed.
E)coating the pipe with a fluoropolymer to act as a source of fluoride ion (since the latter is so hard to oxidize).

Question 32

Which of the halogens in Table 20.1 is the strongest oxidizing agent?

A)Cl₂
B)Br₂
C)F₂
D)I₂
E)All of the halogens have equal strength as oxidizing agents.

Question 33

What is the anode in an alkaline battery?

A)MnO₂
B)KOH
C)Zn powder
D)Mn₂O₃
E)Pt

Question 34

__________ is reduced in the following reaction: Cr₂O₇^2- + 6S₂O₃^2- + 14H⁺ → 2Cr³⁺ + 3S₄O₆^2- + 7H₂O

A)Cr⁶⁺
B)S²⁺
C)H⁺
D)O^2-
E)S₄O₆^2-

Question 35

Which substance is serving as the reducing agent in the following reaction? 14H⁺ + Cr₂O₇^2- + 3Ni → 3Ni²⁺ + 2Cr³⁺ + 7H₂O

A)Ni
B)H⁺
C)Cr₂O₇^2-
D)H₂O
E)Ni²⁺

Question 36

Consider an electrochemical cell based on the reaction: 2H⁺ (aq)+ Sn (s)→ Sn²⁺ (aq)+ H₂ (g)
Which of the following actions would change the measured cell potential?

A)increasing the pH in the cathode compartment
B)lowering the pH in the cathode compartment
C)increasing the [Sn²⁺] in the anode compartment
D)increasing the pressure of hydrogen gas in the cathode compartment
E)Any of the above will change the measure cell potential.

Question 37

__________ is the oxidizing agent in the reaction below. Cr₂O₇^2- + 6S₂O₃^2- + 14H⁺ → 2Cr³⁺ + 3S₄O₆^2- + 7H₂O

A)Cr₂O₇^2-
B)S₂O₃^2-
C)H⁺
D)Cr³⁺
E)S₄O₆^2-

Question 38

__________ is the reducing agent in the reaction below. Cr₂O₇^2- + 6S₂O₃^2- + 14H⁺ → 2Cr³⁺ + 3S₄O₆^2- + 7H₂O

A)Cr₂O₇^2-
B)S₂O₃^2-
C)H⁺
D)Cr³⁺
E)S₄O₆^2-

Question 39

The gain of electrons by an element is called __________.

A)reduction
B)oxidation
C)disproportionation
D)fractionation
E)sublimation

Question 40

Which one of the following is the best oxidizing agent?

A)H₂
B)Na
C)O₂
D)Li
E)Ca

Question 41

__________ electrons appear in the following half-reaction when it is balanced. S₄O₆^2- → S₂O₃^2-

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

Question 42

In a voltaic cell, electrons flow from the __________ to the __________.

A)salt bride, anode
B)anode, salt bridge
C)cathode, anode
D)salt bridge, cathode
E)anode, cathode

Question 43

What is the oxidation number of manganese in MnO₂?

A)+3
B)+2
C)+1
D)+4
E)+7

Question 44

The balanced half-reaction in which sulfate ion is reduced to sulfite ion is a __________ process.

A)four-electron
B)one-electron
C)two-electron
D)three-electron
E)six-electron

Question 45

The standard cell potential (E°_cell)for the voltaic cell based on the reaction below is __________ V. Sn²⁺ (aq)+ 2Fe³⁺ (aq)→ 2Fe²⁺ (aq)+ Sn⁴⁺ (aq)

A)+0.46
B)+0.617
C)+1.39
D)-0.46
E)+1.21

Question 46

1V = __________.

A)1 amp ∙ s
B)1 J/s
C)96485 C
D)1 J/C
E)1 C/J

Question 47

What is the oxidation number of chromium in Cr₂O ion?

A)+3
B)+12
C)+7
D)+6
E)+14

Question 48

What is the oxidation number of manganese in the MnO ion?

A)+1
B)+2
C)+5
D)+4
E)+7

Question 49

The more __________ the value of E°_red, the greater the driving force for reduction.

A)positive
B)negative
C)exothermic
D)endothermic
E)extensive

Question 50

What is the oxidation number of oxygen in H₂O₂?

A)-1
B)-2
C)+1
D)+2
E)-1/2

Question 51

The balanced half-reaction in which dichromate ion is reduced to chromium(III)ion is a __________ process.

A)four-electron
B)twelve-electron
C)three-electron
D)six-electron
E)two-electron

Question 52

The half-reaction occurring at the anode in the balanced reaction shown below is __________. 3MnO₄^- (aq)+ 24H⁺ (aq)+ 5Fe (s)→ 3Mn²⁺ (aq)+ 5Fe³⁺ (aq)+ 12H₂O (l)

A)MnO₄^- (aq)+ 8H⁺ (aq)+ 5e^- → Mn²⁺ (aq)+ 4H₂O (l)
B)2MnO₄^- (aq)+ 12H⁺ (aq)+ 6e^- → 2Mn²⁺ (aq)+ 3H₂O (l)
C)Fe (s)→ Fe³⁺ (aq)+ 3e^-
D)Fe (s)→ Fe²⁺ (aq)+ 2e^-
E)Fe²⁺ (aq)→ Fe³⁺ (aq)+ e^-

Question 53

What is the oxidation number of potassium in KMnO₄?

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

Question 54

The half-reaction occurring at the cathode in the balanced reaction shown below is __________. 3MnO₄^- (aq)+ 24H⁺ (aq)+ 5Fe (s)→ 3Mn²⁺ (aq)+ 5Fe³⁺ (aq)+ 12H₂O (l)

A)MnO₄^- (aq)+ 8H⁺ (aq)+ 5e^- → Mn²⁺ (aq)+ 4H₂O (l)
B)2MnO₄^- (aq)+ 12H⁺ (aq)+ 6e^- → 2Mn²⁺ (aq)+ 3H₂O (l)
C)Fe (s)→ Fe³⁺ (aq)+ 3e^-
D)Fe (s)→ Fe²⁺ (aq)+ 2e^-
E)Fe²⁺ (aq)→ Fe³⁺ (aq)+ e^-

Question 55

The electrode at which oxidation occurs is called the __________.

A)oxidizing agent
B)cathode
C)reducing agent
D)anode
E)voltaic cell

Question 56

Which substance is the reducing agent in the reaction below? Pb + PbO₂ + 2H₂SO₄ → 2PbSO₄ + 2H₂O

A)Pb
B)H₂SO₄
C)PbO₂
D)PbSO₄
E)H₂O

Question 57

The reduction half reaction occurring in the standard hydrogen electrode is __________.

A)H₂ (g, 1 atm)→ 2H⁺ (aq, 1M)+ 2e^-
B)2H⁺ (aq)+ 2OH^- → H₂O (l)
C)O₂ (g)+ 4H⁺ (aq)+ 4e^- → 2H₂O (l)
D)2H⁺ (aq, 1M)+ 2e^- → H₂ (g, 1 atm)
E)2H⁺ (aq, 1M)+ Cl₂ (aq)→ 2HCl (aq)

Question 58

Which substance is the oxidizing agent in the reaction below? Pb + PbO₂ + 2H₂SO₄ → 2PbSO₄ + 2H₂O

A)Pb
B)H₂SO₄
C)PbO₂
D)PbSO₄
E)H₂O

Question 59

The balanced half-reaction in which chlorine gas is reduced to the aqueous chloride ion is a __________ process.

A)one-electron
B)two-electron
C)four-electron
D)three-electron
E)six-electron

Question 60

The balanced half-reaction in which dichromate ion is reduced to chromium metal is a __________ process.

A)two-electron
B)six-electron
C)three-electron
D)four-electron
E)twelve-electron

Question 61

The standard cell potential (E°_cell)of the reaction below is -0.55 V. The value of ΔG° for the reaction is __________ J/mol. I₂ (s)+ 2Br^- (aq)→ 2I^- (aq)+ Br₂ (l)

A)0.54
B)0.55
C)5.5 × 10^-6
D)1.1 × 10⁵
E)none of the above

Question 62

Corrosion of iron is retarded by __________.

A)the presence of salts
B)high pH conditions
C)low pH conditions
D)both the presence of salts and high pH conditions
E)both the presence of salts and low pH conditions

Question 63

The standard cell potential (E°_cell)of the reaction below is +1.34 V. The value of ΔG° for the reaction is __________ kJ/mol. 3Cu (s)+ 2MnO₄^- (aq)+ 8H⁺ (aq)→ 3Cu²⁺ (aq)+ 2MnO₂ (s)+ 4H₂O (l)

A)-24.3
B)+259
C)-259
D)+776
E)none of the above

Question 64

The standard cell potential (E°_cell)for the voltaic cell based on the reaction below is __________ V. 3Sn⁴⁺ (aq)+ 2Cr (s)→ 2Cr³⁺ (aq)+ 3Sn²⁺ (aq)

A)+1.94
B)+0.89
C)+2.53
D)-0.59
E)-1.02

Question 65

A voltaic cell is constructed with two silver-silver chloride electrodes, where the half-reaction is AgCl (s)+ e^- → Ag (s)+ Cl^- (aq)E° = +0.222 V
The concentrations of chloride ion in the two compartments are 0.0222 M and 2.22 M, respectively. The cell emf is __________ V.

A)0.212
B)0.118
C)0.00222
D)22.2
E)0.232

Question 66

The most useful ore of aluminum is bauxite, in which Al is present as hydrated oxides, Al₂O₃ × H₂O. The number of kilowatt-hours of electricity required to produce 4.00 kg of aluminum from electrolysis of compounds from bauxite is __________ when the applied emf is 5.00 V.

A)0.0168
B)0.0596
C)39.7
D)19.9
E)59.6

Question 67

The standard cell potential (E°_cell)for the reaction below is +0.63 V. The cell potential for this reaction is __________ V when [Zn²⁺] = 3.5 M and [Pb²⁺] = 2.0 × 10^-4 M. Pb²⁺ (aq)+ Zn (s)→ Zn²⁺ (aq)+ Pb (s)

A)0.50
B)0.84
C)0.39
D)0.76
E)0.63

Question 68

The lead-containing reactant(s)consumed during recharging of a lead-acid battery is/are __________.

A)Pb (s)only
B)PbO₂ (s)only
C)PbSO₄ (s)only
D)both PbO₂ (s)and PbSO₄ (s)
E)both Pb (s)and PbO₂ (s)

Question 69

The standard cell potential (E°_cell)of the reaction below is -0.34 V. The value of ΔG° for the reaction is __________ kJ/mol. Cu (s)+ 2H⁺ (aq)→ Cu²⁺ (aq)+ H₂ (g)

A)-0.34
B)+66
C)-130
D)+130
E)none of the above

Question 70

The standard cell potential (E°_cell)for the voltaic cell based on the reaction below is __________ V. 2Cr (s)+ 3Fe²⁺ (aq)→ 3Fe (s)+ 2Cr³⁺ (aq)

A)+0.30
B)+2.80
C)+3.10
D)+0.83
E)-0.16

Question 71

The standard cell potential (E°_cell)for the reaction below is +1.10 V. The cell potential for this reaction is __________ V when the concentration of [Cu²⁺] = 1.0 × 10^-5 M and [Zn²⁺] = 3.5 M. Zn (s)+ Cu²⁺ (aq)→ Cu (s)+ Zn²⁺ (aq)

A)1.42
B)1.26
C)0.94
D)0.78
E)1.10

Question 72

Galvanized iron is iron coated with __________.

A)magnesium.
B)zinc.
C)chromium.
D)phosphate.
E)iron oxide.

Question 73

The standard emf for the cell using the overall cell reaction below is +0.48 V: Zn (s)+ Ni²⁺ (aq)→ Zn²⁺ (aq)+ Ni (s)
The emf generated by the cell when [Ni²⁺] = 2.50 M and [Zn²⁺] = 0.100 M is ________ V.

A)0.40
B)0.50
C)0.52
D)0.56
E)0.44

Question 74

A voltaic cell is constructed with two Zn²⁺-Zn electrodes, where the half-reaction is Zn²⁺ + 2e^- → Zn (s)E° = -0.763 V
The concentrations of zinc ion in the two compartments are 5.50 M and 1.11 × 10^-2 M, respectively. The cell emf is __________ V.

A)-1.54 × 10^-3
B)-378
C)0.0798
D)0.160
E)-0.761

Question 75

The standard cell potential (E°_cell)of the reaction below is +0.126 V. The value of ΔG° for the reaction is __________ kJ/mol. Pb (s)+ 2H⁺ (aq)→ Pb²⁺ (aq)+ H₂ (g)

A)-24.3
B)+24.3
C)-12.6
D)+12.6
E)-50.8

Question 76

The standard emf for the cell using the overall cell reaction below is +2.20 V: 2Al (s)+ 3I₂ (s)→ 2Al³⁺ (aq)+ 6I^- (aq)
The emf generated by the cell when [Al³⁺] = 4.5 × 10^-3 M and [I^-] = 0.15 M is ________ V.

A)2.20
B)2.32
C)2.10
D)2.39
E)2.23

Question 77

The standard cell potential (E°_cell)for the voltaic cell based on the reaction below is __________ V. Cr (s)+ 3Fe³⁺ (aq)→ 3Fe²⁺ (aq)+ Cr³⁺ (aq)

A)-1.45
B)+2.99
C)+1.51
D)+3.05
E)+1.57

Question 78

How many kilowatt-hours of electricity are used to produce 3.00 kg of magnesium in the electrolysis of molten MgCl₂ with an applied emf of 4.50 V?

A)0.0336
B)0.0298
C)7.4
D)29.8
E)14.9

Question 79

The standard cell potential (E°)of a voltaic cell constructed using the cell reaction below is 0.76 V: Zn (s)+ 2H⁺ (aq)→ Zn²⁺ (aq)+ H₂ (g)
With PH₂ = 1.0 atm and [Zn²⁺] = 1.0 M, the cell potential is 0.66 V. The concentration of H⁺ in the cathode compartment is __________ M.

A)2.0 × 10^-2
B)4.2 × 10^-4
C)1.4 × 10^-1
D)4.9 × 10¹
E)1.0 × 10^-12

Question 80

The relationship between the change in Gibbs free energy and the emf of an electrochemical cell is given by __________.

A)ΔG =
B)ΔG =
C)ΔG = -nFE
D)ΔG = -nRTF
E)ΔG =