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how to calculate delta Grxn for the following equation? O2(g) + 2H2O(l) + 2Cu (s

ID: 753270 • Letter: H

Question

how to calculate delta Grxn for the following equation? O2(g) + 2H2O(l) + 2Cu (s) -> 4OH^-(aq) + 2Cu^2+ (aq) PLease help!

Explanation / Answer

The two half-reactions are: O2 (g) + 2H2O (l) + 4e- --> 4OH-, E0 = +0.40 V Cu (s) --> Cu2+ + 2e-, E0 = -0.34 V Use these as is, i.e. don't multiply voltages by stoichiometric coefficients. So overall reaction is: O2 (g) + 2H2O (l) + 2Cu (s) --> 4OH- + 2Cu2+, E0 = 0.06V Then use the equation: DG0 = -nFE0 = nF(0.06) n = 4, and F is 96,485 C/mole, so DG0 = -4(96,485)(0.06) = -23156 J, or -23.156 kJ. If your instructor wants you to use correct sig figs, you really want to round to 1 sig fig, which is what you have for the voltage.