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AP Chemistry-Electrochemistry Multiple Choice Identify the choice that best completes the statement or answers the question. ____ 1. The half-reaction that occurs at the cathode during the electrolysis of molten sodium bromide is __________. a. 2Br- → Br2 + 2eb. Br2 + 2e- → 2Brc. Na+ + e- → Na d. Na → Na+ + ee. 2H2O + 2e- → 2OH- + H2 ____ 2. How many coulombs of charge pass through a cell if 2.40 amperes of current are passed through the cell for 85.0 minutes? a. 2.04 × 102 C b. 1.33 × 10-1 C c. 1.22 × 104 C d. 2.12 × 103 C e. 3.40 C ____ 3. How many moles of chromium would be electroplated by passing a current of 5.2 amperes through a solution of Cr2(SO4)3 for 45.0 minutes? a. 0.048 mol b. 2.9 mol c. 0.15 mol d. 6.9 mol e. 0.073 mol ____ 4. An aqueous copper(II) sulfate solution is electrolyzed for 45 minutes. A 3.2 ampere current is used. What mass of copper is produced? a. 0.95 g b. 1.9 g c. 2.8 g d. 4.6 g e. 5.5 g ____ 5. Which response contains all the following statements that are correct, and no others? I. II. III. a. b. c. d. e. In voltaic cells the flow of electrons is spontaneous. In electrolytic cells electrons flow in the external circuit (through the wire) from the anode to the cathode. In voltaic cells the cathode is the positive electrode. I III I and II II and III I, II, and III ____ 6. A cell is constructed by immersing a strip of lead in a 1.0 M Pb(NO3)2 solution and a strip of silver in a 1.0 M AgNO3 solution. The circuit is completed by a wire and a salt bridge. As the cell operates, the strip of silver gains mass (only silver), and the concentration of silver ions in the solution around the silver strip decreases, while the strip of lead loses mass, and the concentration of lead ions increases in the solution around the lead strip. Which of the following represents the reaction that occurs at the cathode in this cell? a. Pb2+ + 2e- → Pb b. Pb → Pb2+ + 2ec. Ag+ + e- → Ag d. Ag → Ag+ + ee. none of the above ____ 7. A voltaic cell is constructed by immersing a strip of copper metal in 1.0 M CuSO4 solution and a strip of aluminum in 0.50 M Al2(SO4)3 solution. A wire and a salt bridge complete the circuit. The aluminum strip loses mass, and the concentration of aluminum ions in the solution increases. The copper electrode gains mass, and the concentration of copper ions decreases. Which of the following are applicable to the electrode at which oxidation occurs? I. II. III. IV. V. VI. a. b. c. d. e. The anode The cathode The positive electrode The electrode at which electrons are produced The negative electrode The electrode at which electrons are used up I, III, and V I, IV, and V II, V, and VI II, III, and IV None of the first four responses contains all the correct choices and no others. ____ 8. Which of the following species is the strongest oxidizing agent? a. Sn2+ b. Sn4+ c. Br2 d. Bre. Li ____ 9. Which of the following is the strongest reducing agent? a. K b. Ag c. Ba2+ d. F2 e. Cu ____ 10. Which of the following metals is most easily oxidized? a. Cd b. Cu c. Fe d. Ni e. Zn ____ 11. Which of the following describes the net reaction that occurs in the cell, Cd|Cd2+(1 M)||Cu2+(1 M)|Cu? a. b. c. d. e. Cu + Cd2+ → Cu2+ + Cd Cu + Cd → Cu2+ + Cd2+ Cu2+ + Cd2+ → Cu + Cd Cu2+ + Cd → Cu + Cd2+ 2Cu + Cd2+ → 2Cu+ + Cd ____ 12. Which one of the following reactions is spontaneous (in the direction given) under standard electrochemical conditions? a. Pb2+ + 2I- → Pb + I2 b. Cu2+ + Fe → Cu + Fe2+ c. 2Au + Pt2+ → 2Au+ + Pt d. Mg2+ + 2Br- → Mg + Br2 e. 2Hg + 2Cl- + 2H+ → Hg2Cl2 + H2 ____ 13. What is the numerical value for the standard cell potential for the following reaction? 2Cr3+(aq) + 3Cu(s) → 2Cr(s) + 3Cu2+(aq) a. b. c. d. e. -1.08 V -0.40 V 0.40 V 1.08 V 2.52 V ____ 14. Calculate the standard cell potential for the cell, Cd|Cd2+(1 M)||Cu2+(1 M)|Cu. a. b. c. d. e. +0.74 V -0.74 V +0.06 V -0.06 V 0.00 V ____ 15. Given the following standard electrode potentials: Half-Reaction O2(g) + 4H+ + 4e- → 2H2O 2CO2(g) + 2H+ + 2e- → (COOH)2 E0 +1.23 V -0.49 V Which response contains all the true statements and no others? (Assume all species are present under standard electrochemical conditions.) I. II. III. IV. V. H2O will spontaneously oxidize (COOH)2 to form CO2. O2(g) will spontaneously oxidize (COOH)2 to form CO2. (COOH)2 will spontaneously reduce O2(g) to form H2O. H+ will spontaneously reduce (COOH)2 to form CO2. CO2 will spontaneously oxidize H2O to form O2(g). a. b. c. d. e. II, IV, and V I, III, and IV II and III I and IV III and V ____ 16. If a copper-plated iron can is scratched, the iron beneath it corrodes more rapidly than it would without the coating. On the other hand, a galvanized iron can is not oxidized if its coating is scratched. Which statement below about these processes is false? a. Copper is less active than iron. b. Zinc is more active than iron. c. The zinc is preferentially reduced. d. Zinc is acting as a sacrificial anode. e. Copper is less easily oxidized than iron. ____ 17. A zinc bar weighing 3.0 kg is attached to a buried iron pipe to protect the pipe from corrosion. An average current of 0.020 A flows between the bar and the pipe. How many years will be required for the zinc bar to be entirely consumed? (1 yr = 3.16 × 107 s) a. 600yr b. 14.0 yr c. 5.99 yr d. 7.00 yr e. 6.66 yr ____ 18. Calculate the reduction potential of the Zn2+/Zn electrode when [Zn2+] = 1.0 × 10-8 M. a. -0.73 V b. -0.75 V c. -0.76 V d. -0.77 V e. -1.00 V ____ 19. A cell is constructed by immersing a strip of silver in 0.10 M AgNO3 solution and a strip of lead in 1.0 M Pb(NO3)2 solution. A wire and salt bridge complete the cell. What is the potential of the silver electrode in the cell? a. 0.74 V b. 0.80 V c. 0.83 V d. 0.86 V e. 0.88 V ____ 20. Calculate Ecell for the reaction below when [Zn2+] = 1.00 M, [H+] = 1.00 × 10-6 M, and Zn(s) + 2H+ → Zn2+ + H2(g) a. b. c. d. e. +0.41 V +0.053 V 0.64 V +1.12 V +0.76 V ____ 21. Calculate the cell potential of the following voltaic cell. = 1.00 atm. Zn|Zn2+(1.0 × 10-4 M)||Cu2+(1.0 × 10-6 M)|Cu a. b. c. d. e. +0.98 V +1.10 V +1.04 V +1.22 V +1.16 V ____ 22. Calculate the Cd2+ concentration in the following cell if Ecell = 0.23 V. Cd(s)|Cd2+(× M)||Ni2+(1.00 M)|Ni a. b. c. d. e. 0.0019 M 1.4 × 10-5 M 0.0036 M 0.015 M 0.0086 M ____ 23. A concentration cell is constructed by placing identical iron electrodes in two Fe2+ solutions. The potential of this cell is observed to be 0.047 V. If the more concentrated Fe2+ solution is 0.10 M, what is the concentration of the other Fe2+ solution? a. 1.5 × 10-2 M b. 2.8 × 10-5 M c. 3.5 × 10-4 M d. 9.2 × 10-2 M e. 2.6 × 10-3 M ____ 24. Calculate ∆G0 for the following reaction from its Evalue. F = 96,500 J/V•mol e-) 3Hg2Cl2 + 2Cr → 2Cr3+ + 6Hg + 6Cla. b. c. d. e. -1.12 × 103 kJ -585 kJ -361 kJ 1.62 × 103 kJ -1.78 × 103 kJ ____ 25. Calculate ∆G for the reaction of the cell below under the stated conditions. F = 96,500 J/V•mol e-) Zn|Zn2+(1.0 × 10-8 M)||Cu2+(1.0 × 10-6 M)|Cu a. b. c. d. e. -163 kJ -192 kJ 201 kJ -212 kJ -268 kJ AP Chemistry-Electrochemistry Answer Section MULTIPLE CHOICE 1. 2. 3. 4. 5. 6. 7. ANS: C PTS: 1 TOP: The Electrolysis of Molten Salts ANS: C PTS: 1 TOP: Faraday's Law of Electrolysis ANS: A PTS: 1 TOP: Faraday's Law of Electrolysis ANS: C PTS: 1 TOP: Faraday's Law of Electrolysis ANS: E PTS: 1 TOP: Voltaic or Galvanic Cells ANS: C PTS: 1 TOP: Voltaic or Galvanic Cells ANS: B A table of standard electrode potentials may be necessary for this question. PTS: 1 TOP: Voltaic or Galvanic Cells 8. ANS: C A table of standard electrode potentials may be necessary for this question. PTS: 1 TOP: Standard Electrode Potentials 9. ANS: A A table of standard electrode potentials may be necessary for this question. PTS: 1 TOP: Standard Electrode Potentials 10. ANS: E A table of standard electrode potentials may be necessary for this question. PTS: 1 TOP: Standard Electrode Potentials 11. ANS: D A table of standard electrode potentials may be necessary for this question. PTS: 1 TOP: Uses of Standard Electrode Potentials 12. ANS: B A table of standard electrode potentials may be necessary for this question. PTS: 1 TOP: Uses of Standard Electrode Potentials 13. ANS: A A table of standard electrode potentials may be necessary for this question. PTS: 1 TOP: Uses of Standard Electrode Potentials 14. ANS: A A table of standard electrode potentials may be necessary for this question. PTS: 1 TOP: Uses of Standard Electrode Potentials 15. ANS: C A table of standard electrode potentials may be necessary for this question. PTS: 1 16. ANS: C TOP: Standard Electrode Potentials for Other Half-Reactions A table of standard electrode potentials may be necessary for this question. PTS: 1 TOP: Corrosion Protection 17. ANS: B A table of standard electrode potentials may be necessary for this question. PTS: 1 TOP: Corrosion Protection 18. ANS: E A table of standard electrode potentials may be necessary for this question. PTS: 1 TOP: The Nernst Equation 19. ANS: A A table of standard electrode potentials may be necessary for this question. PTS: 1 TOP: The Nernst Equation 20. ANS: A A table of standard electrode potentials may be necessary for this question. PTS: 1 TOP: The Nernst Equation 21. ANS: C A table of standard electrode potentials may be necessary for this question. PTS: 1 TOP: The Nernst Equation 22. ANS: A A table of standard electrode potentials may be necessary for this question. PTS: 1 TOP: Using Electrochemical Cells to Determine Concentrations 23. ANS: E A table of standard electrode potentials may be necessary for this question. PTS: 1 24. ANS: B 25. ANS: D TOP: Using Electrochemical Cells to Determine Concentrations PTS: 1 TOP: The Relationship of E... to Delta G0 and K PTS: 1 TOP: The Relationship of E... to Delta G0 and K