PExam-3

# PExam-3 - Name Date 1 Gold(atomic mass = 197 is plated from a solution of chlorauric acid HAuCl4 it deposits on the cathode Calculate the time it

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Name: ___________________________________ Date: ______________ 1. Gold (atomic mass = 197) is plated from a solution of chlorauric acid, HAuCl 4 ; it deposits on the cathode. Calculate the time it takes to deposit 0.54 gram of gold, passing a current of 0.10 amperes. (1 faraday = 96,485 coulombs) A) 46 minutes B) 2.2 hours C) 0.73 hours D) 0.24 hours E) none of these 2. determine the standard potential, °, of a cell that employs the reaction Fe + Cu 2+ Cu + Fe 2+ . Reaction ° (volts) Fe 2+ + 2 e Fe –0.440 Cu 2+ + 2 e Cu +0.340 A) –0.100 B) –0.78 C) 0.1 D) 0.780 E) –0.2 3. Consider the reaction at 25°C for which the following data are relevant: 11.29 kJ/mol 355.33 J/K mol 33.15 kJ/mol 239.90 J/K mol ? 204.80 J/K mol Calculate for the reaction at 25°C. A) –1.35 × 10 5 kJ B) 98.7 kJ C) –25.2 kJ D) 135 kJ E) 0 Page 1

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° depends on temperature. Which of the following equations describes the temperature dependence of °? A) ° = – ln k B) ° = Δ H ° – T Δ S ° C) ° = - D) ln ° = – E) none of these 5. In which case must a reaction be spontaneous at all temperatures? A) Δ H is positive, Δ S is positive. B) Δ H = 0, Δ S is negative. C) Δ S = 0, Δ H is positive. D) Δ H is negative, Δ S is positive. E) none of these 6. For a reaction in a voltaic cell both Δ H ° and Δ S ° are positive. Which of the following statements is true? A) ° cell will increase with an increase in temperature. B) ° cell will decrease with an increase in temperature. C) ° cell will not change when the temperature increases. D) Δ G ° > 0 for all temperatures. E) None of the above statements is true. Use the following to answer question 7. An antique automobile bumper is to be chrome plated. The bumper, which is dipped into an acidic Cr 2 O 7 2– solution, serves as a cathode of an electrolytic cell. The atomic mass of Cr is 51.996; 1 faraday = 96,485 coulombs. Page 2
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## This note was uploaded on 02/25/2011 for the course CHEM 222 taught by Professor Harding during the Fall '08 term at CUNY Hunter.

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PExam-3 - Name Date 1 Gold(atomic mass = 197 is plated from a solution of chlorauric acid HAuCl4 it deposits on the cathode Calculate the time it

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