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32 Electrolytic Cells

32 Electrolytic Cells - Here are the standard reduction...

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1 Here are the standard reduction potentials for 2 half- reactions that occur in a rechargeable Ni/Cd battery. What is the standard cell potential? -0.81 volts Cd(s) + 2OH - (aq) + 2e - Cd(OH) 2 (s) +0.44 volts Ni(OH) 3 (s) + e - Ni(OH) 2 (s) + OH - (aq) G o = - n F E o For a spontaneous reaction, you need G o < 0 and E o cell > 0. A) – 1.25 V B) + 1.25 V C) – 0. 37 V D) + 0.37 V 2 The half-reaction with the more positive reduction potential produces the greater decrease in free energy, so it runs as written, i.e. as a reduction reaction. -0.81 volts Cd(OH) 2 (s) + 2e - Cd(s) + 2OH-(aq) +0.44 volts Ni(OH) 3 (s) + 1 e - Ni(OH) 2 (s) + OH - (aq) E o red G o = - n F E o The other half-reaction then must reverse and run as an oxidation reaction. If a reaction reverses, both G o and E o change sign. E o cell = E o reduction + E o oxidation =+1.25 V E o oxidation = - E o reduction
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