Deck 20: Electrochemistry

Question 1

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

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

Answer 1

2

Question 2

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.

Answer 2

None of the above is a redox reaction.

Question 3

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)

Answer 3

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

Question 4

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 5

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 6

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

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

Question 7

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

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

Question 8

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 9

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 10

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)

Question 11

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 12

Which one of the following is the best oxidizing agent?

A)H₂
B)Na
C)O₂
D)Li
E)Ca

Question 13

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 14

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

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

Question 15

Which transformation below is an example of an oxidation in an electrochemical cell?

A)CO₂ → C₂O₄^2-
B)VO₂⁺ → VO²⁺
C)NO → NO₃^-
D)H₂AsO₄ → H₃AsO₃
E)O₂ → H₂O₂

Question 16

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 17

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 18

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 19

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 20

Which element is oxidized in the reaction below?
Fe²⁺ + H⁺ + Cr₂O₇^2- → Fe³⁺ + Cr³⁺ + H₂O

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

Question 21

________ 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 22

What is the oxidation number of oxygen in K₂O₂?

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

Question 23

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

A)Pb
B)PbSO₄
C)H₂SO₄
D)PbO₂
E)H₂O

Question 24

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

A)S₄O₆^2-
B)Cr
C)H
D)O
E)S

Question 25

The loss of electrons by an element is called ________.

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

Question 26

________ is the reducing agent in the reaction below. Na(s)+ 2Cl₂(g)→ 2NaCl(s)

A)Cl₂
B)NaCl
C)Na⁺
D)Na
E)Cl^-

Question 27

________ is the oxidizing agent in the reaction below. Na(s)+ 2Cl₂(g)→ 2NaCl(s)

A)Na⁺
B)Cl^-
C)Na
D)NaCl
E)Cl₂

Question 28

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 29

Which substance is serving as the oxidizing agent in the following reaction?
CH₄(g)+ 2O₂(g)→ CO₂(g)+ 2H₂O(g)

A)H₂O
B)CH₄
C)O₂
D)CO₂
E)The reaction above is not a redox reaction

Question 30

What is being reduced at the cathode in the hydrogen fuel cell?

A)O₂
B)KOH
C)Li
D)H₂
E)Pt

Question 31

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

A)H
B)Cr
C)O
D)S
E)S₄O₆^2-

Question 32

What is the oxidation number of manganese in MnO₂?

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

Question 33

What is the cathode in an alkaline battery?

A)MnO₂
B)KOH
C)Zn powder
D)Mn₂O₃
E)Pt

Question 34

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 35

What is the oxidation number of oxygen in H₂O₂?

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

Question 36

What is the oxidation number of manganese in KMnO4?

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

Question 37

Which of the statements about cathodic protection of a metal pipe against corrosion is correct?

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

Question 38

Which substance does not undergo oxidation or reduction in the reaction below?
Pb + PbO₂ + 2H₂SO₄ → 2PbSO₄ + 2H₂O

A)Pb
B)H₂SO₄
C)PbO₂
D)PbSO₄
E)The reaction above is not a redox reaction

Question 39

What is the oxidation number of chromium in K₂Cr₂O₇?

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

Question 40

What is the anode in an alkaline battery?

A)MnO₂
B)KOH
C)Zn powder
D)Mn₂O₃
E)Pt

Question 41

The standard cell potential (E°_cell)of the reaction below is +0.126 V.The value of 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 42

The standard cell potential (E°_cell)of the reaction below is -0.55 V.The value of 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 43

The less ________ the value of E°_red,the lower the driving force for reduction.

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

Question 44

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 45

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 46

The standard cell potential (E°_cell)of the reaction below is -0.34 V.The value of 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 47

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 48

The balanced half-reaction in which ethanol,CH₃CH₂OH,is oxidized to ethanoic acid,CH₃COOH. is a ________ process.

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

Question 49

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 50

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 51

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

A)H₂ (g, 1 atm)→ 2H⁺ (aq, 1M)+ 2e^-
B)2H⁺ (aq)+ 2O → 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 52

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

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

Question 53

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 =

Question 54

The electrode at which oxidation occurs is called the ________.

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

Question 55

1V = ________.

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

Question 56

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 57

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 58

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 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 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)+ 5 → 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 61

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 Pb (s)and PbSO₄ (s)
E)both Pb (s)and PbO₂ (s)

Question 62

In the electrochemical cell using the redox reaction below,the oxidation half reaction is ________. (aq)+ Fe (s)→ (aq)+ (aq)

A)Sn⁴⁺ + 2e^- → Sn²⁺
B)Fe → Fe²⁺ + 2e^-
C)Sn⁴⁺ → Sn²⁺ + 2e^-
D)Fe + 2e^- → Fe²⁺
E)Fe + →

Question 63

The standard cell potential ( )for the reaction below is +0.63 V.At 25 °C,the cell potential for this reaction is ________ V when [ ] = 3.0 M and [ ] = (aq)+ Zn (s)→ (aq)+ Pb (s)

A)0.51
B)0.86
C)0.40
D)0.75
E)0.63

Question 64

What is the correct coefficient for the electrons in the following half-reaction: Ni⁶⁺ + ___e^- → Ni

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

Question 65

In the electrochemical cell using the redox reaction below,the cathode half-reaction is ________. 2 (s)+ Sn (s)→ (aq)+ H₂ (g)

A)2H⁺ + 2e^- → H₂
B)Sn → Sn²⁺ + 2e^-
C)2H⁺ → H₂ + 2e^-
D)Sn + 2e^- → Sn²⁺
E)Sn + → H₂

Question 66

In the galvanic cell using the redox reaction below,the reduction half-reaction is ________. Zn (s)+ (aq)→ (aq)+ Cu (s)

A)Cu²⁺ + 2e^- → Cu
B)Zn → Zn²⁺ + 2e^-
C)Cu²⁺ → Cu + 2e^-
D)Zn + 2e^- → Zn²⁺

Question 67

A voltaic cell is constructed with two silver-silver chloride electrodes,where the half-reaction is AgCl (s)+ → Ag (s)+ (aq)E° = +0.222 V
The concentrations of chloride ion in the two compartments are 0.0100 M and 1.55 M,respectively.At 25 °C,the cell emf is ________ V.

A)0.216
B)0.130
C)0.00143
D)34.4
E)0.228

Question 68

Galvanized iron is iron coated with ________.

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

Question 69

What is the oxidation number of nitrogen in the NH₂OH molecule?

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

Question 70

The standard cell potential ( )for the reaction below is +1.10 V.The cell potential for this reaction is ________ V when the concentration of and Zn (s)+ (aq)→ Cu (s)+ (aq)

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

Question 71

Which element is reduced in the reaction below?
Fe²⁺ + H⁺ + Cr₂O₇^2- → Fe³⁺ + Cr³⁺ + O

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

Question 72

The standard cell potential (E°)of a voltaic cell constructed using the cell reaction below is 0.76 V: Zn (s)+ (aq)→ (aq)+ (g)
With = 1.0 atm and [ ] = 1.0 M,the cell potential is 0.53 V.At 25 °C,the concentration of in the cathode compartment is ________ M.

A)1.3 × 10^-4
B)1.7 × 10^-8
C)1.1 × 10^-2
D)7.7 × 10³
E)1.3 × 10^-11

Question 73

Which element is reduced in the following reaction? + 12HN → 2Fe(N + 3S + 6N + 6H₂O

A)N
B)S
C)H
D)O
E)

Question 74

Which substance is the oxidizing agent in the reaction below?
Fe (l)+ 2HI (g)→ Fe (s)+ CO (g)+ (g)

A)HI
B)Fe(CO)₅
C)Fe(CO)₄I₂
D)CO
E)H₂

Question 75

What is the oxidation number of bromine in the HBrO molecule?

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

Question 76

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

A)-24.3
B)+259
C)-259
D)+776
E)-776

Question 77

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 78

What is the oxidation number of sulfur in the S₂O₃^2- ion?

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

Question 79

What is the oxidation number of phosphorous in the PH₃ molecule?

A)-3
B)-4
C)-5
D)+1
E)0

Question 80

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

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