Ans:A Algorithm:No Chapter/Section:18.1 Difficulty:Easy Keyword1:Chemistry

14. For the redox reaction 2Fe2+ + Cl2 ® 2Fe3+ + 2Cl– which of the following are the correct half-reactions?

I. / Cl2 + 2e– ® 2Cl–
II. / Cl ® Cl– + e–
III. / Cl2 ® 2Cl– + 2e–
IV. / Fe2+ ® Fe3+ + e–
V. / Fe2+ + e– ® Fe3+

a) I and IV

b) I and V

c) II and IV

d) II and V

e) III and IV

Ans:a Algorithm:No Chapter/Section:18.1 Difficulty:Easy Keyword1:Chemistry Keyword2:generalchemistry Keyword3:electrochemistry Keyword4:half-reaction

15. What is the oxidation state of Hg in Hg2Cl2?

a) +2

b) –1

c) –2

d) +1

e) 0

Ans:d Algorithm:No Chapter/Section:18.1 Difficulty:Easy Keyword1:Chemistry Keyword2:generalchemistry Keyword3:chemicalreactions Keyword4:typesofchemicalreactions Keyword5:oxidation-reductionreaction Keyword6:assigningoxidationnumber

16. How many electrons are transferred in the following reaction?

2ClO3– + 12H+ + 10I– ® 5I2 + Cl2 + 6H2O

a) 12

b) 5

c) 2

d) 30

e) 10

Ans:e Algorithm:No Chapter/Section:18.1 Difficulty:Easy Keyword1:Chemistry Keyword2:generalchemistry Keyword3:electrochemistry Keyword4:half-reaction Keyword5:balancingchemicalequation

17. How many electrons are transferred in the following reaction?

Cd + 2HCl ® CdCl2 + H2

a) 0

b) 1

c) 2

d) 4

e) not enough information given

Ans:c Algorithm:Yes Chapter/Section:18.1 Difficulty:Easy Keyword1:Chemistry Keyword2:generalchemistry Keyword3:electrochemistry Keyword4:half-reaction Keyword5:balancingoxidation-reductionreactions

Consider a galvanic cell based in the reaction Fe2+ + Cr2O72– ® Fe3+ + Cr3+ in acidic solution.

21. What is the coefficient of Fe3+ in the balanced equation?

a) 6

b) 2

c) 3

d) 4

e) none of these

Ans:a Algorithm:No Chapter/Section:18.1 Difficulty:Easy Keyword1:Chemistry Keyword2:generalchemistry Keyword3:electrochemistry Keyword4:half-reaction Keyword5:balancingoxidation-reductionreactions Keyword6:half-reactionmethod

22. Calculate the voltage of the standard cell carrying out this reaction.

a) 0

b) 0.21 V

c) –0.21 V

d) 0.56 V

e) –0.56 V

Ans:d Algorithm:No Chapter/Section:18.3 Difficulty:Easy Keyword1:Chemistry Keyword2:generalchemistry Keyword3:electrochemistry Keyword4:voltaiccells Keyword5:standard cell emfs and standard electrode potentials Keyword6:calculatingcellemfs

23. Which energy conversion shown below takes place in a galvanic cell?

a) electrical to chemical

b) chemical to electrical

c) mechanical to chemical

d) chemical to mechanical

e) mechanical to electrical

Ans:b Algorithm:No Chapter/Section:18.2 Difficulty:Easy Keyword1:Chemistry Keyword2:generalchemistry Keyword3:electrochemistry Keyword4:voltaiccells

24. Which of the following reactions is possible at the anode of a galvanic cell?

a) Zn ® Zn2+ + 2e–

b) Zn2+ + 2e– ® Zn

c) Zn2+ + Cu ® Zn + Cu2+

d) Zn + Cu2+ ® Zn2+ + Cu

e) two of these

Ans:a Algorithm:No Chapter/Section:18.2 Difficulty:Easy Keyword1:Chemistry Keyword2:generalchemistry Keyword3:electrochemistry Keyword4:voltaiccells Keyword5:constructionofvoltaiccells

25. Which of the following is true for the cell shown here? Zn(s)│Zn2+(aq) ║ Cr3+(aq) │Cr(s)

a) The electrons flow from the cathode to the anode.

b) The electrons flow from the zinc to the chromium.

c) The electrons flow from the chromium to the zinc.

d) The chromium is oxidized.

e) The zinc is reduced.

Ans:b Algorithm:No Chapter/Section:18.2 Difficulty:Moderate Keyword1:Chemistry Keyword2:generalchemistry Keyword3:electrochemistry Keyword4:voltaiccells Keyword5:constructionofvoltaiccells

26. The anode in a voltaic cell and in an electrolytic cell is

a) positive in both cells

b) the site of oxidation and of reduction, respectively

c) the site of reduction and of oxidation, respectively

d) the site of oxidation in both cells

e) the site of reduction in both cells

Ans:d Algorithm:No Chapter/Section:18.2 Difficulty:Easy Keyword1:Chemistry Keyword2:generalchemistry Keyword3:electrochemistry Keyword4:voltaiccells Keyword5:constructionofvoltaiccells difficulty:easy

27. Which statement is always true of the cathode in an electrochemical cell?

a) It is considered the “negative” electrode.

b) It is considered the “positive” electrode.

c) Reduction occurs here.

d) Metal is plated out here.

e) Negative ions flow toward the cathode.

Ans:c Algorithm:No Chapter/Section:18.2 Difficulty:Easy Keyword1:Chemistry Keyword2:generalchemistry Keyword3:electrochemistry Keyword4:voltaiccells Keyword5:constructionofvoltaiccells difficulty:moderate

28. A strip of copper is placed in a 1 M solution of copper nitrate and a strip of silver is placed in a 1 M solution of silver nitrate. The two metal strips are connected to a voltmeter by wires and a salt bridge connects the solutions. The following standard reduction potentials apply:

Ag+(aq) + e– Ag(s) / ℰ° = +0.80 V
Cu2+(aq) + 2e– Cu(s) / ℰ° = +0.34 V

Which of the following statements is false?

a) Electrons flow in the external circuit from the copper electrode to the silver electrode.

b) The silver electrode increases in mass as the cell operates.

c) There is a net general movement of silver ions through the salt bridge to the copper half-cell.

d) Negative ions pass through the salt bridge from the silver half-cell to the copper half-cell.

e) Some positive copper ions pass through the salt bridge from the copper half-cell to the silver half-cell.

Ans:c Algorithm:No Chapter/Section:18.3 Difficulty:Moderate Keyword1:Chemistry Keyword2:generalchemistry Keyword3:electrochemistry Keyword4:voltaiccells Keyword5:constructionofvoltaiccells

29. You are told that metal X is a better reducing agent than metal Y. This must mean that:

a) X+ is a better oxidizing agent than Y+.

b) X+ is a better reducing agent than Y+.

c) Y is a better oxidizing agent than X.

d) Y+ is a better reducing agent than X+.

e) Y+ is a better oxidizing agent than X+.

Ans:e Algorithm:No Chapter/Section:18.3 Difficulty:Easy Keyword1:Chemistry Keyword2:generalchemistry Keyword3:electrochemistry Keyword4:voltaiccells Keyword5:standard cell emfs and standard electrode potentials Keyword6:strength of oxidizing and reducing agents

30. Which of the following species cannot function as an oxidizing agent?

a) S(s)

b) NO3–(aq)

c) Cr2O72–(aq)

d) I–(aq)

e) MnO4–(aq)

31. Which of the following is the strongest oxidizing agent?

MnO4– + 4H+ + 3e– ® MnO2 + 2H2O / ℰ° = 1.68 V
I2 + 2e– ® 2I– / ℰ° = 0.54 V
Zn2+ + 2e– ® Zn / ℰ° = –0.76 V

a) MnO4–

b) I2

c) Zn2+

d) Zn

e) MnO2

Ans:a Algorithm:No Chapter/Section:18.3 Difficulty:Easy Keyword1:Chemistry Keyword2:generalchemistry Keyword3:electrochemistry Keyword4:voltaiccells Keyword5:standard cell emfs and standard electrode potentials Keyword6:strength of oxidizing and reducing agents

32. Which metal, Al or Ni could reduce Zn2+ to Zn(s) if placed in a Zn2+(aq) solution?

Zn2+ + 2e– ® Zn / ℰ° = –0.76 V
Al3+ + 3e– ® Al / ℰ° = –1.66 V
Ni2+ + 2e– ® Ni / ℰ° = –0.23 V

a) Al

b) Ni

c) Both Al and Ni would work.

d) Neither Al nor Ni would work.

e) Cannot be determined.

33. Which of the following is the best reducing agent?

Cl2 + 2e– ® 2Cl– / ℰ° = 1.36 V
Mg2+ + 2e– ® Mg / ℰ° = –2.37 V
2H+ + 2e– ® H2 / ℰ° = 0.00 V

a) Cl2

b) H2

c) Mg

d) Mg2+

e) Cl-

Ans:c Algorithm:No Chapter/Section:18.3 Difficulty:Easy Keyword1:Chemistry Keyword2:generalchemistry Keyword3:electrochemistry Keyword4:voltaiccells Keyword5:standard cell emfs and standard electrode potentials Keyword6:strength of oxidizing and reducing agents

34. Consider the galvanic cell shown below (the contents of each half-cell are written beneath each compartment):

0.50 M Br2 0.20 M Cr3+

0.10 M Br–

The standard reduction potentials are as follows:

Cr3+(aq) + 3e– ® Cr(s) ℰ° = –0.725 V

Br2(aq) + 2e– ® 2Br–(aq) ℰ° = +1.090 V

What is ℰ° for this cell?

a) 1.815 V

b) 0.365 V

c) –0.365 V

d) 4.720 V

e) 1.320 V

Ans:a Algorithm:Yes Chapter/Section:18.3 Difficulty:Easy Keyword1:Chemistry Keyword2:generalchemistry Keyword3:electrochemistry Keyword4:voltaiccells Keyword5:standard cell emfs and standard electrode potentials Keyword6:calculatingcellemfs

35. Consider the galvanic cell shown below (the contents of each half-cell are written beneath each compartment):

0.50 M Br2 0.20 M Cr3+

0.10 M Br–

The standard reduction potentials are as follows:

Cr3+(aq) + 3e– ® Cr(s) ℰ° = -0.73 V

Br2(aq) + 2e– ® 2Br–(aq) ℰ° = +1.09 V

Which of the following statements about this cell is false?

a) This is a galvanic cell.

b) Electrons flow from the Pt electrode to the Cr electrode.

c) Reduction occurs at the Pt electrode.

d) The cell is not at standard conditions.

e) To complete the circuit, cations migrate into the left half-cell and anions migrate into the right half-cell from the salt bridge.

Ans:b Algorithm:No Chapter/Section:18.3 Difficulty:Easy Keyword1:Chemistry Keyword2:generalchemistry Keyword3:electrochemistry Keyword4:voltaiccells Keyword5:constructionofvoltaiccells

36. Refer to the galvanic cell below (the contents of each half-cell are written beneath each compartment):

0.10 M MnO4– 0.40 M Cr3+

0.20 M Mn2+ 0.30 M Cr2O72–

0.010 M H+ 0.010 M H+

The standard reduction potentials are as follows:

MnO4– + 8H+ + 5e– ® Mn2+ + 4H2O, ℰ° = 1.507 V

Cr2O72– + 14H+ + 6e– ® 2Cr3+ + 7H2O, ℰ° = 1.330 V

What is the value of ℰ°cell?

a) –0.177

b) 2.837

c) 0.177

d) 0.677

e) 6.205

Ans:c Algorithm:Yes Chapter/Section:18.5 Difficulty:Moderate Keyword1:Chemistry Keyword2:generalchemistry Keyword3:electrochemistry Keyword4:voltaiccells Keyword5:dependenceofemfonconcentration Keyword6:Nernstequation

Use the following to answer questions 37-44:

Refer to the galvanic cell below (the contents of each half-cell are written beneath each compartment):

0.10 M MnO4– 0.40 M Cr3+

0.20 M Mn2+ 0.30 M Cr2O72–

0.010 M H+ 0.010 M H+

The standard reduction potentials are as follows:

MnO4– + 8H+ + 5e– ® Mn2+ + 4H2O, ℰ° = 1.51 V

Cr2O72– + 14H+ + 6e– ® 2Cr3+ + 7H2O, ℰ° = 1.33 V

37. When current is allowed to flow, which species is oxidized?

a) Cr2O72–

b) Cr3+

c) MnO4–

d) Mn2+

e) H+

Ans:b Algorithm:No Chapter/Section:18.3 Difficulty:Easy Keyword1:Chemistry Keyword2:generalchemistry Keyword3:electrochemistry Keyword4:voltaiccells Keyword5:constructionofvoltaiccells

38. When current is allowed to flow, which species is reduced?

a) Cr2O72–

b) Cr3+

c) MnO4–

d) Mn2+

e) H+

Ans:c Algorithm:No Chapter/Section:18.3 Difficulty:Easy Keyword1:Chemistry Keyword2:generalchemistry Keyword3:electrochemistry Keyword4:voltaiccells Keyword5:constructionofvoltaiccells

39. What is the oxidation state of Cr in Cr2O72–?

a) +7

b) +6

c) +12

d) –1

e) –2

Ans:b Algorithm:No Chapter/Section:18.1 Difficulty:Easy Keyword1:Chemistry Keyword2:generalchemistry Keyword3:chemicalreactions Keyword4:typesofchemicalreactions Keyword5:oxidation-reductionreaction Keyword6:assigningoxidationnumber

40. What is the value of Q, the reaction quotient, for this cell reaction?

a) 6.7 ´ 1040

b) 1.5 ´ 10–41

c) 1.5 ´ 10–4

d) 6.7 ´ 103

e) none of these

Ans:b Algorithm:No Chapter/Section:18.5 Difficulty:Moderate Keyword1:Chemistry Keyword2:generalchemistry Keyword3:electrochemistry Keyword4:voltaiccells Keyword5:dependenceofemfonconcentration

41. In which direction do electrons flow in the external circuit?

a) left to right

b) right to left

c) no current flows; the cell is at equilibrium

d) cannot be determined.

e) none of these

Ans:b Algorithm:No Chapter/Section:18.3 Difficulty:Easy Keyword1:Chemistry Keyword2:generalchemistry Keyword3:electrochemistry Keyword4:voltaiccells Keyword5:constructionofvoltaiccells

45. A cell is set up with copper and lead electrodes in contact with CuSO4(aq) and Pb(NO3)2(aq), respectively, at 25°C. The standard reduction potentials are:

Pb2+ + 2e– ® Pb ℰ° = –0.13 V

Cu2+ + 2e– ® Cu ℰ° = +0.34 V

If the Pb2+ and Cu2+ are each 1.0 M, the potential of the cell, in volts, is:

a) 0.47 V

b) 0.92 V

c) 0.22 V

d) 0.58 V

e) none of these

46. Consider an electrochemical cell with a zinc electrode immersed in 1.0 M Zn2+ and a silver electrode immersed in 1.0 M Ag+.

Zn2+ + 2e– ® Zn ℰ° = –0.755 V

Ag+ + e– ® Ag ℰ° = 0.800 V

Calculate ℰ° for this cell.

a) 0.045 V

b) –0.045 V

c) 1.555 V

d) –1.555 V

e) none of these

Ans:c Algorithm:Yes Chapter/Section:18.3 Difficulty:Easy Keyword1:Chemistry Keyword2:generalchemistry Keyword3:electrochemistry Keyword4:voltaiccells Keyword5:standard cell emfs and standard electrode potentials Keyword6:calculatingcellemfs

47. The galvanic cell described by Zn(s)│Zn2+(aq)║Cu2+(aq)│Cu(s) has a standard cell potential of 1.101 volts. Given that Zn(s) ® Zn2+(aq) + 2e– has an oxidation potential of 0.762 volts, determine the reduction potential for .

a) 1.863 V

b) –1.863 V

c) –0.339 V

d) 0.339 V

e) none of these

Ans:d Algorithm:Yes Chapter/Section:18.3 Difficulty:Moderate Keyword1:Chemistry Keyword2:generalchemistry Keyword3:electrochemistry Keyword4:voltaiccells Keyword5:standard cell emfs and standard electrode potentials

48. The following question refers to a galvanic cell that utilizes the following reaction (unbalanced):

(AuCl4)–(aq) + Cu(s) ® Au(s) + Cl–(aq) + Cu2+(aq)

Given the following information, determine the standard cell potential:

Species / Standard Reduction Potential (V)
Au3+(aq) / 1.4980
Cu2+(aq) / -0.3391

a) 1.1589 V

b) 1.8371 V

c) 3.8158 V

d) 0.8198 V

e) 4.1549 V

49. Choose the correct statement given the following information:

Fe3+(aq) + e– ® Fe2+(aq) ℰ° = 0.77 V

Fe(CN)63–(aq) + e– ® Fe(CN)64–(aq) ℰ° = 0.36 V

a) Fe2+(aq) is more likely to be oxidized than Fe2+ complexed to CN–.

b) Fe3+(aq) is more likely to be reduced than Fe3+ complexed to CN–.

c) Both A and B are true.

d) Complexation of Fe ions with CN– has no effect on their tendencies to become oxidized or reduced.

e) None of these is true.

Ans:b Algorithm:No Chapter/Section:18.3 Difficulty:Easy Keyword1:Chemistry Keyword2:generalchemistry Keyword3:electrochemistry Keyword4:voltaiccells Keyword5:standard cell emfs and standard electrode potentials Keyword6:strength of oxidizing and reducing agents

50. The following question refers to the following system:

3Ag(s) + NO3–(aq) + 4H+(aq) ® 3Ag+(aq) + NO(g) + 2H2O(l)

Anode reaction: Ag ® Ag+(aq) + e– ℰ° = –0.7990 V

Cathode reaction: NO3–(aq) + 4H+(aq) + 3e– ® NO(g) + 2H2O(l) ℰ° = 0.9639 V

Determine the standard cell potential.

a) –1.7629 V

b) 0.1649 V

c) 2.0927 V

d) 3.5258 V

e) 0.5876 V

Ans:b Algorithm:Yes Chapter/Section:18.3 Difficulty:Easy Keyword1:Chemistry Keyword2:generalchemistry Keyword3:electrochemistry Keyword4:voltaiccells Keyword5:standard cell emfs and standard electrode potentials Keyword6:calculatingcellemfs

51. Which of the following would be the best oxidizing agent?

a) Cl2

b) Fe

c) Na

d) Na+