Deck 19: Redox Reactions and Electrochemistry

Question 1

Given the following notation for an electrochemical cell Pt(s)| H₂(g)| H⁺(aq)|| Ag⁺(aq)| Ag(s)
What is the balanced overall (net)cell reaction?

A)2H⁺(aq)+ 2Ag⁺(aq) $\rarr$ H₂(g)+ 2Ag(s)
B)H₂(g)+ 2Ag(s) $\rarr$ H⁺(aq)+ 2Ag⁺(aq)
C)2H⁺(aq)+ 2Ag(s) $\rarr$ H₂(g)+ 2Ag⁺(aq)
D)H₂(g)+ Ag⁺(aq) $\rarr$ H⁺(aq)+ Ag(s)
E)H₂(g)+ 2Ag⁺(aq) $\rarr$ 2H⁺(aq)+ 2Ag(s)

Answer 1

H₂(g)+ 2Ag⁺(aq) $\rarr$ 2H⁺(aq)+ 2Ag(s)

Question 2

Consider an electrochemical cell constructed from the following half cells, linked by a KCl salt bridge. - a Fe electrode in 1.0 M FeCl₂ solution
- a Ni electrode in 1.0 M Ni(NO₃ )₂ solution
When the cell is running spontaneously, which choice includes only true statements and no false ones?

A)The nickel electrode loses mass and the nickel electrode is the cathode.
B)The nickel electrode gains mass and the nickel electrode is the cathode.
C)The iron electrode gains mass and the iron electrode is the anode.
D)The iron electrode loses mass and the iron electrode is the cathode.

Answer 2

The nickel electrode gains mass and the nickel electrode is the cathode.

Question 3

Consider an electrochemical cell constructed from the following half cells, linked by an external circuit and by a KCl salt bridge. - an Al(s)electrode in 1.0 M Al(NO₃)₃ solution
- a Pb(s)electrode in 1.0 M Pb(NO₃)₂ solution
The balanced overall (net)cell reaction is

A)Pb(s)+ Al³⁺(aq) $\rarr$ Pb²⁺(aq)+ Al(s).
B)3Pb(s)+ 2Al³⁺(aq) $\rarr$ 3Pb²⁺(aq)+ 2Al(s).
C)3Pb²⁺(aq)+ 2Al(s) $\rarr$ 3Pb(s)+ 2Al³⁺(aq).
D)Pb²⁺(aq)+ Al(s) $\rarr$ Pb(s)+ Al³⁺(aq).

Answer 3

3Pb²⁺(aq)+ 2Al(s) $\rarr$ 3Pb(s)+ 2Al³⁺(aq).

Question 4

Complete and balance the following redox equation. What is the coefficient of H₂O when the equation is balanced with the set of smallest whole-number coefficients? H₂O + MnO₄^- + I^- $\rarr$ MnO₂ + IO₃^- (basic solution)

A)1
B)2
C)4
D)10
E)None of these.

Question 5

Complete and balance the following redox equation. What is the coefficient of H₂S when the equation is balanced using the set of smallest whole-number coefficients? H₂S + MnO₄^- $\rarr$ Mn²⁺ + SO₄^2- (acidic solution)

A)1
B)2
C)4
D)5
E)None of these.

Question 6

A certain electrochemical cell has for its cell reaction: Zn + HgO $\rarr$ ZnO + Hg
Which is the half-reaction occurring at the anode?

A)HgO + 2e^- $\rarr$ Hg + O^2-
B)Zn²⁺ + 2e^- $\rarr$ Zn
C)Zn $\rarr$ Zn²⁺ + 2e^-
D)ZnO + 2e^- $\rarr$ Zn

Question 7

Consider an electrochemical cell constructed from the following half cells, linked by a KCl salt bridge. - an Al(s)electrode in 0.5 M Al₂(SO₄)₃ solution
- a Pb(s)electrode in 1.0 M Pb(NO₃)₂ solution
Which electrode is the anode?

A)Al
B)Pb
C)Neither

Question 8

Complete and balance the following redox equation using the smallest whole-number coefficients. What is the coefficient of Sn in the balanced equation? Sn + HNO₃ $\rarr$ SnO₂ + NO₂ + H₂O (acidic solution)

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

Question 9

Complete and balance the following redox equation. The sum of the smallest whole-number coefficients is Br₂ $\rarr$ BrO₃^- + Br^- (basic solution)

A)9.
B)12.
C)18.
D)21.
E)None of the above.

Question 10

Complete and balance the following redox equation. The sum of the smallest whole-number coefficients is Bi(OH)₃ + SnO₂^2- $\rarr$ Bi + SnO₃^2- (basic solution)

A)32.
B)25.
C)16.
D)13.
E)None of these.

Question 11

Complete and balance the following redox equation that occurs in acidic solution using the set of smallest whole-number coefficients. What is the sum of all the coefficients in the equation? PbO₂(s)+ Cl^- $\rarr$ Pb²⁺ + Cl₂(g)(acidic solution)

A)2
B)4
C)5
D)9
E)11

Question 12

Consider an electrochemical cell constructed from the following half cells, linked by a KCl salt bridge. - a Fe electrode in 1.0 M FeCl₂ solution
- a Sn electrode in 1.0 M Sn(NO₃ )₂ solution
When the cell is running spontaneously, which choice includes only true statements and no false ones?

A)The tin electrode loses mass and the tin electrode is the cathode.
B)The tin electrode gains mass and the tin electrode is the cathode.
C)The iron electrode gains mass and the iron electrode is the anode.
D)The iron electrode loses mass and the iron electrode is the cathode.
E)The iron electrode gains mass and the iron electrode is the cathode.

Question 13

Complete and balance the following redox equation. When properly balanced using the smallest whole-number coefficients, the coefficient of S is H₂S + HNO₃ $\rarr$ S + NO (acidic solution)

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

Question 14

Complete and balance the following redox equation. The sum of the smallest whole-number coefficients is MnO₄^- + H⁺ + Br^- $\rarr$ Mn²⁺ + Br₂ + H₂O (acidic solution)

A)6.
B)17.
C)21.
D)29.
E)43.

Question 15

Complete and balance the following redox equation. What is the coefficient of H₂O when the equation is balanced using the set of smallest whole-number coefficients? MnO₄^- + SO₃^2- $\rarr$ Mn²⁺ + SO₄^2- (acidic solution)

A)3
B)4
C)5
D)8
E)None of these.

Question 16

Complete and balance the following redox equation using the set of smallest whole-numbers coefficients. What is the sum of the coefficients?
HI + HNO₃ $\rarr$ I₂ + NO (acidic solution)

A)5
B)7
C)14
D)17
E)None of these.

Question 17

Calculate the value of E°_cell for the following reaction: 2Au(s)+ 3Ca²⁺(aq) $\rarr$ 2Au³⁺(aq)+ 3Ca(s)

A)-4.37 V
B)-1.37 V
C)-11.6 V
D)1.37 V
E)4.37 V

Question 18

Complete and balance the following redox equation using the set of smallest whole-number coefficients. Now sum the coefficients of all species in the balanced equation. (Remember the coefficients that are equal to one.)The sum of the coefficients is BrO₃^-(aq)+ Sb³⁺(aq) $\rarr$ Br^-(aq)+ Sb⁵⁺(aq)(acidic solution)

A)4.
B)12.
C)13.
D)17.
E)None of these.

Question 19

Complete and balance the following redox equation. What is the coefficient of OH^- when the equation is balanced using the set of smallest whole-number coefficients? MnO₄^- + I^- $\rarr$ MnO₂ + IO₃^- (basic solution)

A)1
B)2
C)4
D)10
E)None of these.

Question 20

Calculate E°_cell for a silver-aluminum cell in which the cell reaction is Al(s)+ 3Ag⁺(aq) $\rarr$ Al³⁺(aq)+ 3Ag(s)

A)-2.46 V.
B)0.86 V.
C)-0.86 V.
D)2.46 V.
E)none of these.

Question 21

Consider the following electrochemical cell: U | U³⁺(aq)|| Cl^-(aq),Cl₂(g)| Pt
If the standard cell emf is 3.16 V, what is the standard reduction potential for uranium?

A)-3.16 V
B)+3.16 V
C)-1.80 V
D)+1.80 V
E)+1.36 V

Question 22

Consider the following standard reduction potentials in acid solution: The strongest oxidizing agent among those shown above is

A)Fe³⁺.
B)Fe²⁺.
C)Br^-.
D)Al³⁺.
E)Al.

Question 23

The overall reaction 2Co³⁺(aq)+ 2Cl^-(aq) $\rarr$ 2Co²⁺(aq)+ Cl₂(g)has the standard cell voltage E°_cell = 0.46 V. Given E° = 1.36 V for the reaction Cl₂(g)+ 2e^- $\rarr$ 2Cl^-(aq), calculate the standard reduction potential for the following the half reaction at 25°C: Co³⁺ + e^- $\rarr$ Co²⁺

A)1.82 V
B)-0.90 V
C)0.90 V
D)-1.82 V
E)-1.36 V

Question 24

Consider the following standard reduction potentials in acid solution: Which is the weakest oxidizing agent in this list?

A)Al³⁺(aq)
B)Al(s)
C)I^-(aq)
D)I₂(s)
E)Sn⁴⁺(aq)

Question 25

Calculate E°_cell for the following reaction: 2Fe²⁺(aq)+ Cd²⁺(aq) $\rarr$ 2Fe³⁺(aq)+ Cd(s)

A)-0.37 V
B)0.37 V
C)-1.17 V
D)1.17 V
E)None of these.

Question 26

An electrochemical cell based on the following reaction has a standard cell voltage (E°_cell)of 0.48 V: Sn(s)+ Cu²⁺(aq) $\rarr$ Sn²⁺(aq)+ Cu(s)
What is the standard reduction potential of tin(II)? (E°(Cu²⁺/Cu)= 0.34 V)

A)-0.14 V
B)0.14 V
C)-0.82 V
D)0.82 V
E)none of these

Question 27

Consider the following standard reduction potentials in acid solution: The weakest reducing agent listed above is

A)Cr³⁺.
B)Cr.
C)Mn²⁺.
D)Co.
E)MnO₄^-.

Question 28

In the following half equation, which is the oxidizing agent? NO₃^-(aq)+ 4H⁺(aq)+ 3e^- $\rarr$ NO(g)+ 2H₂O

A)NO₃^-
B)H⁺
C)e^-
D)NO
E)H₂O

Question 29

Consider the following standard reduction potentials in acid solution: The strongest reducing agent listed above is

A)Cr³⁺.
B)Cr.
C)Mn²⁺.
D)Co.
E)MnO₄^-.

Question 30

Using a table of standard electrode potentials, decide which of the following statements is completely true.

A)Cu²⁺ can oxidize H₂, and Fe can reduce Mn²⁺.
B)Ni²⁺ can oxidize Cu²⁺, and Fe²⁺ can reduce H⁺.
C)Fe²⁺ can oxidize H₂, and Fe²⁺ can reduce Au³⁺.
D)Br₂ can oxidize Ni, and H₂ can reduce Mn²⁺.
E)H⁺ can oxidize Fe, and Ni can reduce Br₂.

Question 31

For the reaction Ni²⁺(aq)+ 2Fe²⁺(aq) $\rarr$ Ni(s)+ 2Fe³⁺(aq), the standard cell potential E°_cell is

A)+2.81 V.
B)+1.02 V.
C)+0.52 V.
D)-1.02 V.
E)-2.81 V.

Question 32

Which one of the following reactions will occur spontaneously at standard-state conditions and 25°C?

A)Mg²⁺ + Ca $\rarr$ Mg + Ca²⁺
B)Au + 3K⁺ $\rarr$ Au³⁺ + 3K
C)2Al³⁺ + 3Fe $\rarr$ 2Al + 3Fe²⁺
D)Cu + 2H⁺ $\rarr$ Cu²⁺ + H₂

Question 33

Which statement is true for a spontaneous redox reaction carried out at standard-state conditions?

A)E°_red is always negative.
B)E°_cell is always positive.
C)E°_ox is always positive.
D)E°_red is always positive.

Question 34

Consider the following standard reduction potentials in acid solution: The strongest oxidizing agent listed above is

A)Cr³⁺.
B)Cr.
C)Mn²⁺.
D)Co²⁺.
E)MnO₄^-.

Question 35

Consider the following standard reduction potentials in acid solution: The strongest reducing agent among those shown above is

A)Fe³⁺.
B)Fe²⁺.
C)Br^-.
D)Al³⁺.
E)Al.

Question 36

Consider an electrochemical cell based on the following cell diagram: Pt | Pu³⁺(aq), Pu⁴⁺(aq)|| Cl₂(g), Cl^- (aq)| Pt
Given that the standard cell emf is 0.35 V and that the standard reduction potential of chlorine is 1.36 V, what is the standard reduction potential E°(Pu⁴⁺/Pu³⁺)?

A)2.37 V
B)1.01 V
C)-1.71 V
D)-1.01 V
E)1.71 V

Question 37

Consider a voltaic cell based on the following cell reaction: Ni(s)+ At₂(s) $\rarr$ Ni²⁺(aq)+ 2At^- (aq)
Given that the standard cell emf is 0.55 V, what is the standard reduction potential for astatine? [E°(Ni²⁺/Ni)= -0.25 V]

A)0.80 V
B)0.30 V
C)-0.30 V
D)-0.80 V
E)0.43 V

Question 38

According to the following cell diagram, which chemical species undergoes reduction? Sn | Sn²⁺ || NO₃^- (acid soln), NO(g)| Pt

A)Sn
B)Sn²⁺
C)NO₃^-
D)NO
E)Pt

Question 39

For the reaction, 2Cr²⁺ + Cl₂(g) $\rarr$ 2Cr³⁺ + 2Cl^-, E°_cell is 1.78 V. Calculate E°_cell for the related reaction Cr³⁺ + Cl^- $\rarr$ Cr²⁺ + ¹/₂Cl₂(g).

A)1.78 V
B)0.89 V
C)-1.78 V
D)-0.89 V
E)None of these.

Question 40

Calculate the standard cell emf for the following cell: Mg | Mg²⁺ || NO₃^- (acid soln)| NO(g)| Pt

A)3.33 V
B)1.41 V
C)-1.41 V
D)8.46 V
E)-8.46 V

Question 41

Determine the equilibrium constant (K_eq)at 25°C for the reaction Cl₂(g)+ 2Br^- (aq) $\rarr$ 2Cl^- (aq)+ Br₂(l)

A)1.5 * 10^-10
B)6.3 * 10⁹
C)1.3 * 10⁴¹
D)8.1 * 10⁴
E)9.8

Question 42

Consider the following reaction: 2Fe²⁺(aq)+ Cu²⁺ $\rarr$ 2Fe³⁺(aq)+ Cu. When the reaction comes to equilibrium, what is the cell voltage?

A)0.43 V
B)1.11 V
C)0.78 V
D)-0.43 V
E)0 V

Question 43

Which one of the following reagents is capable of transforming Br^- (aq)to Br₂(l)under standard-state conditions?

A)I^- (aq)
B)NO₃^- (aq)
C)Ag⁺ (aq)
D)Al³⁺ (aq)
E)Au³⁺ (aq)

Question 44

Given the following standard reduction potentials, Ag⁺(aq)+ e^- $\rarr$ Ag(s)E° = 0.80 V
Ag(NH₃)₂⁺(aq)+ e^- $\rarr$ Ag(s)+ 2NH₃(aq)E° = 0.04 V
Calculate the formation constant of Ag(NH₃)₂⁺ at 25°C.

A)6.1 * 10^-15
B)1.5 *10^-13
C)6.9 * 10¹²
D)1.6 * 10¹⁴
E)None of these

Question 45

Using a table of standard reduction potentials, determine which of these reactions (if any)is/are nonspontaneous in the direction indicated at 25°C.

A)2Fe³⁺ + 2Cl^- $\rarr$ 2Fe²⁺ + Cl₂(g)
B)2Fe³⁺ + 2Br^- $\rarr$ 2Fe²⁺ + Br₂(l)
C)2Fe³⁺ + 2I^- $\rarr$ 2Fe²⁺ + I₂(s)
D)A and B
E)All are spontaneous.

Question 46

Which of the following species is the strongest oxidizing agent under standard-state conditions?

A)Ag⁺(aq)
B)H₂(g)
C)H⁺(aq)
D)Cl₂(g)
E)Al³⁺(aq)

Question 47

Determine the equilibrium constant, K_eq, at 25°C for the reaction 2Br^- (aq)+ I₂(s) $\rarr$ Br₂(l)+ 2I^- (aq)

A)5.7 * 10^-19
B)18.30
C)1.7 * 10⁵⁴
D)1.9 * 10¹⁸
E)5.7 * 10^-55

Question 48

Which one of the following reagents is capable of transforming Cu²⁺(1 M)to Cu(s)?

A)I^- (1 M)
B)Ni(s)
C)Al³⁺ (1 M)
D)F^- (1 M)
E)Ag(s)

Question 49

Calculate the cell emf for the following reaction: Cu²⁺(0.10 M)+ H₂(1 atm) $\rarr$ Cu(s)+ 2H⁺(pH = 3.00)

A)0.49 V
B)0.19 V
C)0.15 V
D)0.40 V
E)-0.34 V

Question 50

Which one of the following reagents is capable of transforming Cu(s)to Cu²⁺ (1 M)?

A)I^- (1 M)
B)Ni(s)
C)Ag⁺ (1 M)
D)Al³⁺ (1 M)
E)H⁺ (1 M)

Question 51

Calculate the cell voltage for the following reaction: Cu²⁺ (0.010 M)+ H₂(1 atm) $\rarr$ Cu(s)+ 2H⁺(pH = 7.0)

A)0.19 V
B)-0.01 V
C)0.34 V
D)0.69 V
E)0.49 V

Question 52

Consider an electrochemical cell based on the spontaneous reaction 2AgCl(s)+ Zn(s) $\rarr$ 2Ag(s)+ 2Cl^- + Zn²⁺.
If the zinc ion concentration is kept constant at 1 M, and the chlorine ion concentration is decreased from 1 M to 0.001 M, the cell voltage should

A)increase by 0.06 V.
B)increase by 0.18 V.
C)decrease by 0.06 V.
D)decrease by 0.18 V.
E)increase by 0.35 V.

Question 53

For the electrochemical cell Pt(s)| H₂(1 atm)| H⁺(1 M)|| Cu²⁺(1 M)| Cu(s), which one of the following changes will cause an increase in the cell voltage?

A)Lower the H₂(g)pressure.
B)Increase the size/mass of the copper electrode.
C)Lower the H⁺(aq)concentration.
D)Decrease the concentration of Cu²⁺ ion.
E)None of the above.

Question 54

For the electrochemical cell Ni(s)| Ni²⁺(1 M)|| H⁺(1 M)| H₂(1 atm)| Pt(s), which one of the following changes will cause a decrease in the cell voltage?

A)Increase the pressure of H₂ to 2.0 atm.
B)Decrease the mass of the nickel electrode.
C)Lower the pH of the cell electrolyte.
D)Decrease the concentration of Ni²⁺ ion.
E)None of the above.

Question 55

The half-cell reaction for the oxidation of H₂O(l)to O₂(g)is given below. 2H₂O(l) $\rarr$ O₂(g)+ 4H⁺(aq)+ 4e^-
Which choice lists all of the following species that can oxidize H₂O to O₂(g)under standard-state conditions?
MnO₄^-(aq), Cl₂(g), Pb²⁺(aq), Cl^- (aq), Ag⁺(aq)

A)Cl^-(aq)only
B)Cl₂(g)only
C)Pb²⁺(aq)and Ag⁺(aq)
D)Cl^-(aq)and MnO₄^-(aq)
E)MnO₄^-(aq)and Cl₂(g)

Question 56

Consider an electrochemical cell with the following cell reaction where all reactants and products are at standard-state conditions: Cu²⁺(aq)+ H₂(g) $\rarr$ Cu(s)+ 2H⁺(aq). Predict the effect on the emf of this cell of adding NaOH solution to the hydrogen half-cell until the pH equals 7.0.

A)The emf will increase.
B)The emf will decrease.
C)No change in the emf will be observed.

Question 57

Calculate the cell emf for the following reaction at 25°C: Ni(s)+ 2Cu²⁺(0.010 M) $\rarr$ Ni²⁺(0.0010 M)+ 2Cu⁺(1.0 M)

A)0.40 V
B)-0.43 V
C)0.43 V
D)0.34 V
E)0.37 V

Question 58

Given the following standard reduction potentials, Ag⁺(aq)+ e^- $\rarr$ Ag(s)E° = 0.80 V
AgCN(s)+ e^- $\rarr$ Ag(s)+ CN^-(aq)E° = -0.01 V
Calculate the solubility product of AgCN at 25°C.

A)4.3 * 10^-14
B)2.3 * 10¹³
C)2.1 * 10^-14
D)5.1 * 10¹³
E)None of these

Question 59

Which one of the following reagents is capable of transforming Fe³⁺ (1 M)to Fe²⁺ (1 M)?

A)H₂(1 atm)
B)NO₃^- (1 M)
C)O₂(1 atm)
D)Br^- (1 M)
E)H⁺ (1 M)

Question 60

Calculate the cell emf for the following reaction at 25°C: 2Ag⁺(0.010 M)+ H₂(1 atm) $\rarr$ 2Ag(s)+ 2H⁺(pH = 10.0)

A)1.04 V
B)1.27 V
C)0.92 V
D)0.56 V
E)0.80 V

Question 61

How many coulombs of charge are required to cause reduction of 0.20 mole of Cr³⁺ to Cr?

A)0.60 C
B)3.0 C
C)2.9 * 10⁴ C
D)5.8 * 10⁴ C
E)9.65 * 10⁴ C

Question 62

The measured voltage of a cell in which the following reaction occurs is 0.96 V: H₂(g, 1.0 atm)+ 2Ag⁺(aq, 1.0 M) $\rarr$ 2H⁺(aq, pH = ?)+ 2Ag(s)
Calculate the pH of the H⁺(aq)solution.

A)1.4
B)2.7
C)5.4
D)7.1
E)14.9

Question 63

Predict the products of the electrolysis of aqueous aluminum bromide AlBr₃(aq). (Balancing is not required.)

A)Al + Br₂
B)Al + O₂ + H⁺
C)H₂ + OH^- + Br₂
D)H₂ + O₂

Question 64

How many coulombs of charge are required to cause reduction of 0.25 mole of Cu²⁺ to Cu?

A)0.25 C
B)0.50 C
C)1.2 * 10⁴ C
D)2.4 * 10⁴ C
E)4.8 * 10⁴ C

Question 65

The half-reaction that occurs at the cathode during electrolysis of an aqueous CuCl₂ solution is

A)Cu⁺ + e^- $\rarr$ Cu.
B)Cu²⁺ + e^- $\rarr$ Cu⁺.
C)2H₂O + 2e^- $\rarr$ H₂ + 2OH^-.
D)Cl₂ + 2e^- $\rarr$ 2Cl^-.
E)2Cl^- $\rarr$ Cl₂ + 2e^-.

Question 66

Under standard-state conditions, which of the following half-reactions occurs at the cathode during the electrolysis of aqueous nickel sulfate at 25°C?

A)2H₂O $\rarr$ O₂ + 4H⁺ + 4e^-
B)Ni²⁺ + 2e^- $\rarr$ Ni
C)2H₂O + 2e^- $\rarr$ H₂ + 2OH^-
D)Ni $\rarr$ Ni²⁺ + 2e^-

Question 67

The half-reaction that should occur at the anode during electrolysis of an aqueous potassium bromide solution is

A)Br₂ + 2e^- $\rarr$ 2Br^-.
B)Na $\rarr$ Na⁺ + e^-.
C)Na⁺ + e^- $\rarr$ Na.
D)2Br^- $\rarr$ Br₂ + 2e^-.
E)2H₂O $\rarr$ O₂ + 4H⁺ + 4e^-.

Question 68

If the measured voltage of the cell Zn(s)| Zn²⁺(aq)|| Ag⁺(aq)| Ag(s)is 1.37 V when the concentration of Zn²⁺ ion is 0.010 M, what is the Ag⁺ ion concentration?

A)2.5 M
B)4.0 * 10^-9 M
C)6.2 * 10^-3 M
D)2.6 * 10^-51 M
E)6.2 * 10^-5 M

Question 69

The measured voltage of the cell Pt(s)| H₂ (1.0 atm)| H⁺(aq)|| Ag⁺(1.0 M)| Ag(s)is 1.02 V at 25°C. Calculate the pH of the solution.

A)1.86
B)1.69
C)3.72
D)3.89
E)7.43

Question 70

Which one of the following reactions must be carried out in an electrolytic cell rather than in a galvanic cell?

A)Zn²⁺ + Ca $\rarr$ Zn + Ca²⁺
B)Al³⁺ + 3Br^- $\rarr$ Al + (3/2)Br₂
C)2Al + 3Fe²⁺ $\rarr$ 2Al³⁺ + 3Fe
D)H₂ + I₂(s) $\rarr$ 2H⁺ + 2I^-

Question 71

A current of 2.50 A was passed through an electrolytic cell containing molten CaCl₂ for 4.50 hours. How many moles of calcium metal should be deposited?

A)5.83 * 10^-5 mol
B)0.210 mol
C)0.420 mol
D)0.840 mol
E)1.95 * 10⁹ mol

Question 72

How many faradays are transferred in an electrolytic cell when a current of 2.0 amperes flows for 12 hours?

A)24 F
B)8.6 * 10⁴ F
C)0.90 F
D)6.2 * 10 ^-3 F
E)1.1 F

Question 73

A metal object is to be gold-plated by an electrolytic procedure using aqueous AuCl₃ electrolyte. Calculate the number of moles of gold deposited in 3.0 min by a constant current of 10. A.

A)6.2 * 10^-3 mol
B)9.3 * 10^-3 mol
C)1.8 * 10^-2 mol
D)3.5 * 10^-5 mol
E)160 mol

Question 74

A current of 0.80 A was applied to an electrolytic cell containing molten CdCl₂ for 2.5 hours. Calculate the mass of cadmium metal deposited.

A)3.2 * 10^-7 g
B)1.2 * 10^-3 g
C)4.2 g
D)8.4 g
E)16.8 g

Question 75

Consider an electrochemical cell involving the overall reaction 2AgBr(s)+ Pb(s) $\rarr$ Pb²⁺ + 2Ag(s)+ 2Br^-
Each half-reaction is carried out in a separate compartment. The anion included in the lead half-cell is NO₃^-. The cation in the silver half-cell is K⁺. The two half-cells are connected by a KNO₃ salt bridge. If [Pb²⁺] = 1.0 M, what concentration of Br^- ion will produce a cell emf of 0.25 V at 298 K?
Given: AgBr(s)+ e^- $\rarr$ Ag + Br^-, E° = +0.07 V.

A)0.02 M
B)0.14 M
C)0.38 M
D)1.0 M
E)7.0 M

Question 76

Calculate the minimum voltage required for the electrolysis of 1.0 M NaCl in neutral solution. 2H₂O + 2Cl^- (1.0 M) $\rarr$ H₂(1 atm)+ Cl₂(1 atm)+ 2OH^- (1 * 10^-7 M)

A)2.19 V
B)1.78 V
C)0.41 V
D)-0.41 V
E)-1.78 V

Question 77

The half-reaction that occurs at the cathode during electrolysis of an aqueous sodium iodide solution is

A)Na⁺ + e^- $\rarr$ Na.
B)Na $\rarr$ Na⁺ + e^-.
C)2H₂O + 2e^- $\rarr$ H₂ + 2OH^-.
D)I₂ + 2e^- $\rarr$ 2I^-.
E)2I^- $\rarr$ I₂ + 2e^-.

Question 78

When an aqueous solution of AgNO₃ is electrolyzed, a gas is observed to form at the anode. The gas is

A)H₂.
B)O₂.
C)NO.
D)NO₂.

Question 79

The half-reaction occurring at the cathode during electrolysis of an aqueous copper(II)iodide solution is

A)I₂ + 2e^- $\rarr$ 2I^-.
B)Cu $\rarr$ Cu²⁺ + 2e^-.
C)Cu²⁺ + 2e^- $\rarr$ Cu.
D)2I^- $\rarr$ I₂ + 2e^-.
E)2e^- + 2H₂O $\rarr$ H₂ + 2OH^-.

Question 80

Predict the products obtained from electrolysis of a 1 M AlBr₃ solution. Note that 2H₂O(l)+ 2e^- $\rarr$ H₂(g)+ 2OH^-(aq), E°_red = -0.83 V, and
O₂(g)+ 4H⁺(aq)+ 4e^- $\rarr$ 2H₂O(l), E°_red = +1.23 V

A)Al and Br₂
B)Al and O₂
C)H₂ and O₂
D)H₂ and Br₂
E)Al and H₂