Deck 20: Electrochemistry

Question 1

Which of the following reactions will occur spontaneously as written?

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

Answer 1

3Sn⁴⁺ (aq) + 2Cr (s) -2Cr³⁺ (aq) + 3Sn²⁺ (aq)

Question 2

Consider an electrochemical cell based on the reaction:

Which of the following actions would not change the measured cell potential?

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

Answer 2

addition of more tin metal to the anode compartment

Question 3

Using Table 20.1, which substance can be oxidized by O₂ (g) in acidic aqueous solution?

A) Ni²⁺ (aq)
B) Br^- (aq)
C) Cu²⁺ (aq)
D) Ag (s)
E) Br₂ (l)

Answer 3

Br₂ (l)

Question 4

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 5

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

A) F₂
B) Cl₂
C) Br₂
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) CO₂ -C₂O₄^2-
B) O₂ -H₂O₂
C) VO₂⁺ - VO²⁺
D) NO - NO₃^-
E) H₂AsO₄ -H₃AsO₃

Question 7

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

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

Question 8

The standard cell potential (E°) of a voltaic cell constructed using the cell reaction below is 0.76 V:

With P_H2 = 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) 4.2 × 10^{- 4}
B) 1.0 × 10^{- 12}
C) 4.9 × 10¹
D) 2.0 × 10^{- 2}
E) 1.4 × 10^{- 1}

Question 9

Which element is oxidized in the reaction below?

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

Question 10

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

Question 11

What is the anode in an alkaline battery ?

A) Mn₂O₃
B) MnO₂
C) KOH
D) Pt
E) Zn powder

Question 12

The electrolysis of molten AlCl₃ for 3.25 hr with an electrical current of 15.0 A produces
G of aluminum metal.

A) 16.4
B) 4.55 × 10^{- 3}
C) 147
D) 0.606
E) 49.1

Question 13

Which one of the following is the best oxidizing agent ?

A) O₂
B) Na
C) H₂
D) Ca
E) Li

Question 14

Consider an electrochemical cell based on the reaction:

Which of the following actions would change the measured cell potential?

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

Question 15

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

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

Question 16

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

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

Question 17

Which substance is the reducing agent in the following reaction?

A) NO₂
B) Fe₂S₃
C) H₂O
D) S
E) HNO₃

Question 18

A voltaic cell is constructed with two Zn²⁺- Zn electrodes, where the half- reaction is 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) - 378
B) - 0.761
C) 0.160
D) - 1.54 × 10^{- 3}
E) 0.0798

Question 19

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

Question 20

Which of the following reactions will occur spontaneously as written?

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

Question 21

A voltaic cell is constructed with two silver- silver chloride electrodes, where the half- reaction is The concentrations of chloride ion in the two compartments are 0.0222 M and 2.22 M, respectively.
The cell emf is V.

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

Question 22

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

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

Question 23

Which one of the following reactions is a redox reaction?

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

Question 24

Calculate the number of grams of aluminum produced in 30 minutes by electrolysis of AlCl₃ at a current of 12 A.

Question 25

What is the coefficient of the permanganate ion when the following equation is balanced?

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

Question 26

How many seconds are required to produce 4.00 g of aluminum metal from the electrolysis of molten AlCl₃ with an electrical current of 12.0 A?

A) 27.0
B) 3.57 × 10³
C) 1.19 × 10³
D) 9.00
E) 2.90 × 10⁵

Question 27

The town of Natrium, West Virginia, derives its name from the sodium produced in the electrolysis of molten sodium chloride (NaCl) mined from ancient salt deposits. The number of kilowatt- hours of electricity required to produce 4.60 kg of metallic sodium from the electrolysis of molten NaCl(s) is when the applied emf is 4.50 V.

A) 48.3
B) 12.1
C) 0.0241
D) 0.0414
E) 24.1

Question 28

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

Question 29

The standard emf for the cell using the overall cell reaction below is +2.20 V:

The emf generated by the cell when [Al³⁺] = 4.5 × 10^{- 3} M and [I^- ] = 0.15 M is V.

A) 2.30
B) 2.23
C) 2.39
D) 2.10
E) 2.20

Question 30

The dependence of cell emf on concentration is expressed in the .

Question 31

What is the coefficient of Fe³⁺ when the following equation is balanced?

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

Question 32

The potential (E) to move K⁺ from the extracellular fluid to the intracellular fluid necessitates work. The sign for this potential is _ _.

Question 33

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

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

Question 34

In the formula ΔG = - nFE , F is the _.

Question 35

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

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

Question 36

The major product of a hydrogen fuel cell is .

Question 37

The most difficult species to reduce and the poorest oxidizing agent is _ .

Question 38

Using Table 20.1, which substance can oxidize I^- (aq) to I₂ (s) ?

A) Ag (s)
B) Br₂ (l)
C) Cu²⁺ (aq)
D) Ni²⁺ (aq)
E) Br^- (aq)

Question 39

The standard emf for the cell using the overall cell reaction below is +0.48 V:

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) 0.44
E) 0.56

Question 40

The quantity of charge passing a point in a circuit in one second when the current is one ampere is called a .

Question 41

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

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

Question 42

How many minutes will it take to plate out 2.19 g of chromium metal from a solution of Cr³⁺ using a current of 35.2 amps in an electrolyte cell ?

A) 17.3
B) 1.92
C) 5.77
D) 346
E) 115

Question 43

The half- reaction occurring at the anode in the balanced reaction shown below is .

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

Question 44

What is the oxidation number of manganese in the Mn O ^1- ion?

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

Question 45

Corrosion of iron is retarded by .

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

Question 46

How many seconds are required to produce 1.0 g of silver metal by the electrolysis of a AgNO₃ solution using a current of 30 amps _ ?

A) 3.7 × 10^{- 5}
B) 3.2 × 10³
C) 2.7 × 10⁴
D) 60
E) 30

Question 47

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

Question 48

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

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

Question 49

Galvanized iron is iron coated with .

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

Question 50

What current (in a) is required to plate out 1.22 g of nickel from a solution of Ni²⁺ in 1.0 hour __________ ?

A) 12.9
B) 1.11
C) 4.01 × 10³
D) 2.34
E) 65.4

Question 51

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

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

Question 52

A voltaic cell can be constructed of the same species as long as the are different.

Question 53

1V = .

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

Question 54

The standard cell potential (E°_cell) for the voltaic cell based on the reaction below is V.

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

Question 55

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

A) - 24
B) +24
C) - 12
D) +12
E) - 50

Question 56

is the oxidizing agent in the reaction below.

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

Question 57

The anode of the alkaline battery is powdered zinc in a gel that contacts .

Question 58

At constant temperature and pressure the Gibbs free energy value is a measure of the
of a process.

Question 59

When iron is coated with a thin layer of zinc to protect against corrosion, the iron is said to be .

Question 60

The standard cell potential (E°_cell) for the voltaic cell based on the reaction below is V.

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

Question 61

Which substance is serving as the reducing agent in the following reaction?

A) Ni²⁺
B) Cr₂O₇^2-
C) Ni
D) H⁺
E) H₂O

Question 62

electrons appear in the following half- reaction when it is balanced.

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

Question 63

The electrode at which oxidation occurs is called the .

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

Question 64

Which substance is the reducing agent in the reaction below?

A) PbSO₄
B) Pb
C) H₂SO₄
D) PbO₂
E) H₂O

Question 65

How many grams of copper will be plated out by a current of 2.3 A applied for 25 minutes to a 0.50- M solution of copper(II) sulfate _ ?

A) 0.019
B) 1.8 × 10^{- 2}
C) 1.1
D) 2.2
E) 0.036

Question 66

is reduced in the following reaction:

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

Question 67

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

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

Question 68

How many grams of CuS are obtained by passing a current of 12 A through a solution of CuSO₄ for 15 minutes ?

A) 7.1
B) 14
C) 1.8
D) 3.6
E) 0.016

Question 69

The standard cell potential (E°_cell) for the reaction below is +0.63 V. The cell potential for this reaction is V when [ Zn²⁺] = 1.0 M and [Pb²⁺] = 2.0 × 10^{- 4} M.

A) 0.74
B) 0.85
C) 0.52
D) 0.63
E) 0.41

Question 70

How many grams of Ca metal are produced by the electrolysis of molten CaBr₂ using a current of
30)0 amp for 10.0 hours ?

A) 448
B) 0.0622
C) 112
D) 224
E) 22.4

Question 71

The standard cell potential (E°_cell) for the voltaic cell based on the reaction below is V.

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

Question 72

The gain of electrons by an element is called .

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

Question 73

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

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

Question 74

What is the oxidation number of potassium in KMnO₄?

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

Question 75

What is the oxidation number of manganese in MnO₂?

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

Question 76

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

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

Question 77

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

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

Question 78

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

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

Question 79

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⁺] = 1.0 M.

A) 1.25
B) 0.95
C) 1.10
D) 0.80
E) 1.40

Question 80

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

A) ΔG = ^{- nF}
ERT
B) ΔG = ^{- nF}
E
C) ΔG = - nFE
D) ΔG = - nRTF
E) ΔG = ^{- E}
NF