1

CHAPTER 5 REVIEW

1. The following represents the process used to produce iron from iron III oxide:

Fe2O3 + 3CO → 2Fe + 3CO2 What is the reducing agent in this process?

A. Fe

B. CO

C. CO2

D. Fe2O3

2. Consider the following reaction: 2HNO2 + 2I- + 2H

+ → 2NO + I2 +2H2O

The oxidation number for each nitrogen atom

A. increases by 1

B. increases by 2

C. decreases by 1

D. decreases by 2

3. Which of the following reactions is spontaneous?

A. 2I- + Ag → Ag

+ + I2

B. Co2+

+ Cu → Co + Cu2+

C. Cu2+

+ Pb → Pb2+

+ Cu

D. Ni2+ + 2Ag → 2Ag

+ + Ni

4. Consider the following redox reaction for a lead-acid storage cell:

Pb + PbO2 + 4H+ + 2SO4

2- → 2PbSO4 + 2H2O

The balanced, reduction half reaction is

A. Pb + SO42-

→ 2PbSO4 + 2e-

B. Pb + 2H+ + SO4

2- → PbSO4 + 2H2O + 2e

-

C. PbO2 + 4H+ + SO4

2- + 2e

- → 2PbSO4 + 2H2O

D. PbO2 + 2SO42 + 2H2O + 2e

- → PbSO4 + 2OH

-

5. Consider the following reaction: Cd2+

(aq) + Zn(s) → Cd(s) + Zn2+

(aq)

The potential for the reaction is +0.36 V. What is the reduction potential for the cadmium ion?

A. -1.12 V

B. -0.40 V

C. +0.40 V

D. +1.12 V

6. Which of the following involves a nonspontaneous redox reaction?

A. fuel cell

B. electroplating

C. redox titration

D. carbon dry cell

7. Consider the following redox reaction:

2MnO4- + 16H

+ + 5Sn

2+ → 2Mn

2+ + 8H2O + 5Sn

4+

In a redox titration, 0.60 mole of KMnO4 reacts completely with a solution of Sn(NO3)2. How

many moles of Sn(NO3)2 were present in the solution?

A. 0.024 moles

B. 0.060 moles

C. 1.5 moles

D. 0.30 moles

2

8. Which of the following is not a redox reaction?

A. Cu + Br2 → CuBr2

B. CO + H2O → CO2 + H2

C. CH4 + H2O → CO2 + 2H2O

D. NaOH + HCl → NaCl + H2O

9. What is the minimum voltage required to form nickel from an aqueous solution of NiI2 using inert

electrodes?

A. 0.26 V B. 0.28 V C. 0.54 V D. 0.80 V

10. What substances are formed at the anode and cathode during electrolysis of molten sodium

chloride?

Anode Cathode

A. O2 H2

B. Na Cl2

C. Cl2 H2

D. Cl2 Na

11. A solution containing an unknown cation reacts spontaneously with both zinc and copper. The

unknown cation is

A. 1.0 M H+

B. 1.0 M Ag+

C. 1.0 M Sr2+

D. 1.0 M Mn2+

12. Which of the following half-reactions are balanced?

A. ClO- + H2O + e

- → Cl2 + 2OH

-

B. 2ClO- + H2O + 2e

- → Cl2 + 3OH

-

C. 2ClO- + 2H2O + 2e

- → Cl2 + 4OH

-

D. 2ClO- + 2H2O → Cl2 + 4OH

- + 2e

-

13. Which of the following is a spontaneous redox reaction?

A. Ag+ + I

- → AgI

B. Ag+ + Fe

2+ → Ag + Fe

3+

C. 3Ag+ + Au → 3Ag + Au

3+

D. 2Ag+ + Ni

2+ → 2Ag + Ni

14. Salting the roads during the winter increases the amount of corrosion of cars. The is because the

salt

A. reacts with the iron

B. provides an electrolyte

C. acts as a reducing agent

D. acts as an oxidizing agent

3

Consider the following electrochemical cell for the next five questions.

15. The half-reaction that occurs at the anode is

A. Ni → N2+

+ 2e-

B. Ni2+

→ 2e- + Ni

C. Cu → Cu2+

+ 2e-

D. Cu2+

→ 2e- + Cu

16. The half-reaction that occurs at the cathode is

A. Ni → N2+

+ 2e-

B. Ni2+

+ 2e- → Ni

C. Cu → Cu2+

+ 2e-

D. Cu2+

+ 2e- → Cu

17. The cell potential or Eo is

A. 0.41 V B. 0.78 V C. 0.34 V D. 0.60 V

18. The following ions migrate to the Cu electrode

A. K+ Cu

2+ Ni

2+

B. Cu2+

Ni2+

C. Cl- NO3

-

D. Cl- NO3

- 2e

-

19. The electrons flow

A. through the salt bridge from Cu to Ni

B. through the salt bridge from Cu to Ni

C. through the wire from Cu to Ni

D. through the wire from Ni to Cu

20. Which of the following will not react spontaneously with 1.0 M HCl?

A. tin

B. lithium

C. mercury

D. magnesium

Ni Cu

1.0 M KCl

1M Cu(NO3)2

1M Ni(NO3)2

voltmeter

4

21. Which of the following can be produced by electrolysis from a 1.0 M aqueous solution containing

its ion?

A. nickel

B. sodium

C. aluminum

D. magnesium

22. In order for an electrolytic cell to operate, it must have

A. a voltmeter.

B. a salt bridge.

C. a power supply.

D. an aqueous solution.

23. In the electrolysis of molten ZnCl2 using carbon electrodes, the reaction that occurs at the anode is

A. Zn → Zn2+

+ 2e-

B. Zn2+

+ 2e- → Zn

C. 2Cl- → Cl2 + 2e

-

D. Cl2 + 2e- → 2Cl

-

24. In the electrolysis of aqueous zinc chloride, the half-reaction at the cathode is

A. Cl2 + 2e- → 2Cl

-

B. 2Cl- → Cl2 + 2e

-

C. Zn2+

+ 2e- → Zn

D. Zn → Zn2+

+ 2e-

25. The corrosion of iron can be prevented by attaching a piece of

A. Mn B. Cu C. Pb D. Sn

26. The oxidation number of carbon in CaC2O4 is

A. +2 B. +3 C. +4 D. +6

27. To plate a nickel coin with copper,

A. the nickel coin must be the cathode.

B. the cathode must be made out of copper

C. the electrons must flow to the anode

D. the solution must contain nickel ions

5

Consider the following electrochemical cell for the next five questions.

28. Which of the following statements apply to this electrochemical cell?

I Electrons flow through the wire toward the copper electrode.

II The copper electrode increases in mass.

III Anions move toward the Zn half-cell.

A. I and II only

B. I and III only

C. II and III only

D. I, II, and III

29. The balanced equation for the overall reaction is

A. Zn + Cu2+

→ Cu + Zn2+

B. Cu + Zn2+

→ Zn + Cu2+

C. Zn2+

+ Cu → Cu2+

+ Zn

D. Cu + Zn → Zn2+

+ Cu2+

30. At equilibrium the voltage of the above cell is

A. -1.10 V B. 0.00 V C. +0.42 V D. +1.10 V

31. This redox reaction occurs because

A. Zn is a stronger oxidizing agent than Cu

B. Zn is a stronger reducing agent than Cu

C. Zn2+

is a stronger oxidizing agent than Cu2+

D. Zn2+

is a weaker reducing agent than Cu2+

32. The initial cell voltage at 25 oC is

A. -1.10 V

B. +1.10 V

C. +0.91 V

D. +0.86 V

Zn Cu

1.0 M KNO3

1M Cu(NO3)2

1M Zn(NO3)2

voltmeter

6

33. Consider the following redox reaction: Co2+

(aq) + 2Ag(s) → 2Ag+

(aq) + Co(s)

The reaction is

A. spontaneous and Eo is positive

B. spontaneous and Eo is negative

C. non-spontaneous and Eo is positive

D. non-spontaneous and Eo is negative

34. When MnO4- reacts to form Mn

2+, the manganese in MnO4

- is

A. reduced as its oxidation number increases

B. reduced as its oxidation number decreases

C. oxidized as its oxidation number increases

D. oxidized as its oxidation number decreases

35. The electrolyte used in the alkaline battery is

A. KCl

B. NaOH

C. H2SO4

D. KOH

36. The electrolyte used in an automobile battery is

A. KCl

B. NaOH

C. H2SO4

D. KOH

37. The anode used in the commercial production of Aluminum is

A. C

B. Pt

C. Al

D. AL2O3

38. The anode and cathode used in the electrorefining of impure lead to pure lead are

Anode Cathode

A. Pure Pb Impure Pb

B. Impure Pb Pure Pb

C. Pb2+

Pb

D. Pb Pb2+

39. The anode in the Zinc or common dry cell is

A. C

B. Zn

C. Mg

D. KOH

40. Which of the following are electrolytic cells

I Electrowinning

II Electroplating

III Charging a car battery

IV Fuel cell

A. I and II only

B. I, II, and III only

C. II and II only

D. I, II, III, and IV

7

Subjective

1. Balance the following in basic solution.

MnO4- + C2O4

2- → MnO2 + CO2 (basic)

2. Consider the electrolysis of 1.0 M H2SO4 using platinum electrodes.

a) Write the oxidation half-reaction

b) Write the reduction half-reaction

c) Write the overall reaction and determine the minimum theoretical voltage required.

Consider the following diagram for the electrorefinning of lead.

a) On the diagram, label the anode and cathode.

b) Write the formula for a suitable electrolyte

c) Write the equation for the reduction half-reaction.

Power Source

Impure Pb

Pure Pb

8

4. Describe two chemically different methods that can be used to prevent corrosion of iron and

explain why each method works.

Method 1:

Explanation:

Method 2:

Explanation:

5. The data below were obtained in a redox titration of a 25.00 mL sample containing Sn2+

ions using

0.125 M KMnO4 according to the following reaction:

2MnO4- + 16H

+ + 5Sn

2+ → 2Mn

2+ + 8H2O + 5Sn

4+

Volume of KMnO4 used (mL)

Trial 1 Trial 2 Trial 3

Initial burette reading 2.00 13.80 24.55

Final burette reading 13.80 24.55 35.32

6. A student wanted to electroplate a coin with copper.

a) Identify a suitable anode

b) Identify an appropriate electrolyte

c) To which battery terminal (positive or negative) should the coin be connected?

7. Consider the electrolysis of molten magnesium chloride.

a) Identify the product at the anode.

b) Write the equation for the reduction half-reaction.

9

c) Write the equation for the overall reaction.

8. Consider the following electrochemical cell.

a) Write the anode reaction

b) Write the cathode reaction

c) Write the overall reaction and determine the initial cell potential (Eo).

d) Explain in words how the electrons move through the cell.

e) List all of the ions that migrate toward the Sn electrode.

f) Which electrode loses mass?

g) What is the purpose of the salt bridge?

h) What is the cell potential once equilibrium is achieved

Mn Sn

1.0 M KNO3

1M Sn(NO3)2

1M MnNO3)2

voltmeter

10

UNIT 5 REVIEW - SOLUTIONS

1. The following represents the process used to produce iron from iron III oxide:

Fe2O3 + 3CO → 2Fe + 3CO2 What is the reducing agent in this process?

A. Fe

B. CO

C. CO2

D. Fe2O3

2. Consider the following reaction: 2HNO2 + 2I- + 2H

+ → 2NO + I2 +2H2O

The oxidation number for each nitrogen atom

A. increases by 1

B. increases by 2

C. decreases by 1

D. decreases by 2

3. Which of the following reactions is spontaneous?

A. 2I- + Ag → Ag

+ + I2

B. Co2+

+ Cu → Co + Cu2+

C. Cu2+

+ Pb → Pb2+

+ Cu

D. Ni2+ + 2Ag → 2Ag

+ + Ni

4. Consider the following redox reaction for a lead-acid storage cell:

Pb + PbO2 + 4H+ + 2SO4

2- → 2PbSO4 + 2H2O

The balanced, reduction half reaction is

A. Pb + SO42-

→ 2PbSO4 + 2e-

B. Pb + 2H+ + SO4

2- → PbSO4 + 2H2O + 2e

-

C. PbO2 + 4H+ + SO4

2- + 2e

- → 2PbSO4 + 2H2O

D. PbO2 + 2SO42 + 2H2O + 2e

- → PbSO4 + 2OH

-

5. Consider the following reaction: Cd2+

(aq) + Zn(s) → Cd(s) + Zn2+

(aq)

The potential for the reaction is +0.36 V. What is the reduction potential for the cadmium ion?

A. -1.12 V

B. -0.40 V

C. +0.40 V

D. +1.12 V

6. Which of the following involves a nonspontaneous redox reaction?

A. fuel cell

B. electroplating

C. redox titration

D. carbon dry cell

7. Consider the following redox reaction: 2MnO4- + 16H

+ + 5Sn

2+ → 2Mn

2+ + 8H2O + 5Sn

4+

11

In a redox titration, 0.60 mole of KMnO4 reacts completely with a solution of Sn(NO3)2. How many

moles of Sn(NO3)2 were present in the solution?

A. 0.024 moles

B. 0.060 moles

C. 1.5 moles

D. 0.30 moles

8. Which of the following is not a redox reaction?

A. Cu + Br2 → CuBr2

B. CO + H2O → CO2 + H2

C. CH4 + H2 → CO2 + 2H2O

D. NaOH + HCl → NaCl + H2O

9. What is the minimum voltage required to form nickel from an aqueous solution of NiI2 using inert

electrodes?

A. 0.26 V

B. 0.28 V

C. 0.54 V

D. 0.80 V

10. What substances are formed at the anode and cathode during electrolysis of molten sodium chloride?

Anode Cathode

A. O2 H2

B. Na Cl2

C. Cl2 H2

D. Cl2 Na

11. A solution containing an unknown cation reacts spontaneously with both zinc and copper. The

unknown cation is

A. 1.0 M H+

B. 1.0 M Ag+

C. 1.0 M Sr2+

D. 1.0 M Mn2+

12

12. Which of the following half-reactions are balanced?

A. ClO- + H2O + e

- → Cl2 + 2OH

-

B. 2ClO- + H2O + 2e

- → Cl2 + 3OH

-

C. 2ClO- + 2H2O + 2e

- → Cl2 + 4OH

-

D. 2ClO- + 2H2O → Cl2 + 4OH

- + 2e

-

13. Which of the following is a spontaneous redox reaction?

A. Ag+ + I

- → AgI

B. Ag+ + Fe

2+ → Ag + Fe

3+

C. 3Ag+ + Au → 3Ag + Au

3+

D. 2Ag+ + Ni

2+ → 2Ag + Ni

14. Salting the roads during the winter increases the amount of corrosion of cars. The is because the salt

A. reacts with the iron

B. provides an electrolyte

C. acts as a reducing agent

D. acts as an oxidizing agent

Consider the following electrochemical cell for the next five questions.

15. The half-reaction that occurs at the anode is

A. Ni → Ni2+

+ 2e-

B. Ni2+

→ 2e- + Ni

C. Cu → Cu2+

+ 2e-

D. Cu2+

→ 2e- + Cu

16. The half-reaction that occurs at the cathode is

A. Ni → N2+

+ 2e-

B. Ni2+

+ 2e- → Ni

Ni Cu

1.0 M KCl

1M Cu(NO3)2

1M Ni(NO3)2

voltmeter

13

C. Cu → Cu2+

+ 2e-

D. Cu2+

+ 2e- → Cu

17. The cell potential or Eo is

A. 0.41 V

B. 0.78 V

C. 0.34 V

D. 0.60 V

18. The following ions migrate to the Cu electrode

A. K+ Cu

2+ Ni

2+

B. Cu2+

Ni2+

C. Cl- NO3

-

D. Cl- NO3

- 2e

-

19. The electrons flow

A. through the salt bridge from Cu to Ni

B. through the salt bridge from Cu to Ni

C. through the wire from Cu to Ni

D. through the wire from Ni to Cu

20. Which of the following will not react spontaneously with 1.0 M HCl?

A. tin

B. lithium

C. mercury

D. magnesium

21. Which of the following can be produced by electrolysis from a 1.0 M aqueous solution containing its

ion?

A. nickel

B. sodium

C. aluminum

D. magnesium

22. In order for an electrolytic cell to operate, it must have

A. a voltmeter.

B. a salt bridge.

C. a power supply.

D. an aqueous solution.

23. In the electrolysis of molten ZnCl2 using carbon electrodes, the reaction that occurs at the anode is

14

A. Zn → Zn2+

+ 2e-

B. Zn2+

+ 2e- → Zn

C. 2Cl- → Cl2 + 2e

-

D. Cl2 + 2e- → 2Cl

-

24. In the electrolysis of aqueous zinc chloride, the half-reaction at the anode is

A. Cl2 + 2e- → 2Cl

-

B. 2Cl- → Cl2 + 2e

-

C. Zn2+

+ 2e- → Zn

D. Zn → Zn2+

+ 2e-

25. The corrosion of iron can be prevented by attaching a piece of

A. Mn

B. Cu

C. Pb

D. Sn

26. The oxidation number of carbon in CaC2O4 is

A. +2

B. +3

C. +4

D. +6

27. To plate a nickel coin with copper,

A. the nickel coin must be the cathode.

B. the cathode must be made out of copper

C. the electrons must flow to the anode

D. the solution must contain nickel ions

Consider the following electrochemical cell for the next five questions.

Zn Cu

1.0 M KNO3

1M Cu(NO3)2

1M Zn(NO3)2

voltmeter

15

28. Which of the following statements apply to this electrochemical cell?

I Electrons flow through the wire toward the copper electrode.

II The copper electrode increases in mass.

III Anions move toward the Zn half-cell.

A. I and II only

B. I and III only

C. II and III only

D. I, II, and III

29. The balanced equation for the overall reaction is

A. Zn + Cu2+

→ Cu + Zn2+

B. Cu + Zn2+

→ Zn + Cu2+

C. Zn2+

+ Cu → Cu2+

+ Zn

D. Cu2+

+ Zn → Zn2+

+ Cu

30. At equilibrium the voltage of the above cell is

A. -1.10 V

B. 0.00 V

C. +0.42 V

D. +1.10 V

31. This redox reaction occurs because

A. Zn is a stronger oxidizing agent than Cu

B. Zn is a stronger reducing agent than Cu

C. Zn2+

is a stronger oxidizing agent than Cu2+

D. Zn2+

is a weaker reducing agent than Cu2+

32. The initial cell voltage at 25 oC is

A. -1.10 V

B. +1.10 V

C. +0.91 V

D. +0.86 V

33. Consider the following redox reaction: Co2+

(aq) + 2Ag(s) → 2Ag+

(aq) + Co(s)

The reaction is

A. spontaneous and Eo is positive

B. spontaneous and Eo is negative

C. non-spontaneous and Eo is positive

D. non-spontaneous and Eo is negative

34. When MnO4- reacts to form Mn

2+, the manganese in MnO4

- is

16

A. reduced as its oxidation number increases

B. reduced as its oxidation number decreases

C. oxidized as its oxidation number increases

D. oxidized as its oxidation number decreases

35. The electrolyte used in the alkaline battery is

A. KCl

B. NaOH

C. H2SO4

D. KOH

36. The electrolyte used in an automobile battery is

A. KCl

B. NaOH

C. H2SO4

D. KOH

37. The anode used in the commercial production of Aluminum is

A. C

B. Pt

C. Al

D. AL2O3

38. The anode and cathode used in the electrorefining of impure lead to pure lead are

Anode Cathode

A. Pure Pb Impure Pb

B. Impure Pb Pure Pb

C. Pb2+

Pb

D. Pb Pb2+

39. The anode in the LeClanche or common dry cell is

A. C

B. Zn

C. Mg

D. KOH

40. Which of the following are electrolytic cells

I Electrowinning

II Electroplating

III Charging a car battery

17

IV Fuel cell

A. I and II only

B. I, II, and III only

C. II and II only

D. I, II, III, and IV

18

Subjective

1. Balance the following in basic solution.

MnO4- + C2O4

2- → MnO2 + CO2 (basic)

2(MnO4- + 4H

+ +

3e

- → MnO2 + 2H2O )

3(C2O42-

→ 2CO2 + 2e-)

Acid: 2MnO4- + 3C2O4

2- + 8H

+ → 2MnO2 + 6CO2 + 4H2O

Basic: 2MnO4- + 3C2O4

2- + 4H2O → 2MnO2 + 6CO2 + 8OH

-

2. Consider the electrolysis of 1.0 M H2SO4 using platinum electrodes.

a) Write the oxidation half-reaction

H2O → 1/2O2 + 2H+ + 2e

- E

o = -0.82 V

b) Write the reduction half-reaction

SO42-

+ 4H+ + 2e

- → H2SO3 + H2O E

o = +0.17 V

c) Write the overall reaction and determine the minimum theoretical voltage required.

SO42-

+ 4H+ → 1/2O2 + 2H

+ + H2SO3 E

o = -0.65 V

MTV = +0.65 V

19

3. Consider the following diagram for the electrorefinning of lead.

a) On the diagram, label the anode and cathode.

b) Write the formula for a suitable electrolyte

Pb(NO3)2

c) Write the equation for the reduction half-reaction.

Pb2+

+ 2e- → Pb(s)

4. Describe two chemically different methods that can be used to prevent corrosion of iron and

explain why each method works.

Method 1: Painting

Explanation: Prevents reactants H2O and O2 from contacting the iron

Method 2: Attach some Zn

Explanation: Fe is forced to be the cathode and cannot oxidize

5. The data below were obtained in a redox titration of a 25.00 mL sample containing Sn2+

ions using

0.125 M KMnO4 according to the following reaction:

2MnO4- + 16H

+ + 5Sn

2+ → 2Mn

2+ + 8H2O + 5Sn

4+

Volume of KMnO4 used (mL)

Power Source

Anode Impure Pb

Cathode Pure Pb

20

Trial 1 Trial 2 Trial 3

Initial burette reading 2.00 13.80 24.55

Final burette reading 13.80 24.55 35.32

11.80 10.75 10.77

Average last two to get 10.76 mL

Calculate the [Sn2+

]

[Sn2+

] = 0.01076 L x 0.125 mole x 5 moles Sn2+

1 L 2 moles MnO4-

0.0250 L

= 0.135 M

6. A student wanted to electroplate a coin with copper.

a) Identify a suitable anode Cu

b) Identify an appropriate electrolyte CuSO4

c) To which battery terminal (positive or negative) should the coin be connected?

Negative

7. Consider the electrolysis of molten magnesium chloride.

a) Identify the product at the anode.

Cu2+

b) Write the equation for the reduction half-reaction.

Mg2+

+ 2e- →→→→ Mg(s)

c) Write the equation for the overall reaction.

Mg2+

+ 2Cl- →→→→ Mg(s) + Cl2

8. Consider the following electrochemical cell.

Mn Sn

1.0 M KNO3

voltmeter

21

Cathode Anode

a) Write the anode reaction

Sn2+

+ 2e-

→→→→ Sn

b) Write the cathode reaction

Mn →→→→ Mn2+

+ 2e-

c) Write the overall reaction and determine the initial cell potential (Eo).

Sn2+

+ Mn →→→→ Mn2+

+ Sn

d) Explain in words how the electrons move through the cell.

From anode Mn to cathode Sn

e) List all of the ions that migrate toward the Sn electrode.

Sn2+

Mn2+

K+

f) Which electrode loses mass?

Anode Sn

g) What is the purpose of the salt bridge?

To allow cations and anions to flow from one half cell to the other

h) What is the cell potential once equilibrium is achieved?

0.00 v