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CH 302 13 Answer Key More Advanced Electrochemistry Problems 1. (a) Calculate the mass of copper metal produced at the cathode during the passage of 2.50 amps of current through a solution of copper (II) sulfate for 50.0 minutes. Cu 2+ + 2e - Cu (reduction/cathode) 1 mol 2(6.02 x 10 23 )e - 1 mol 63.5 g 2(9.65 x 10 4 C) 63.5g 50.0 min x (60s/1 min) x (2.50C/s) = 7.50 x 10 3 C 7.50 x 10 3 C x (1 mol e - /9.65 x 10 4 C) x (63.5 g Cu/2 mol e - ) = 2.47 g Cu (b) What volume of oxygen gas (measured at STP) is produced by the oxidation of water at the anode in the electrolysis of copper(II) sulfate in part (a)? 2H 2 O O 2 + 4H + + 4e - (oxidation/anode) 1 mol 4((6.02 x 10 23 )e - 22.4 L 4(9.65 x 10 4 C) 7.50 x 10 3 C x (1 mol e - /9.65 x 10 4 C) x (22.4 L O 2 /4 mol e - ) = 0.435 L O 2 2. What is the E ° for the following electrochemical cell where Zn is the cathode? Zn | Zn 2+ (1.0 M ) || Fe 2+ (1.0 M ) | Fe E ° (Zn) = -0.76 E ° (Fe) = -0.44 E cell = E ° cathode - E ° anode = -0.76 – (-0.44) = -0.32 3. For the electrolysis of molten sodium bromide, write the two half-reactions and show write which electrode at which each occurs (cathode or anode). Two half-reactions:

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