Plz help me how to solve it.

Question

Cn somebody plz tell me why i am getting wring ans

Use tabulated half-cell potentials to calculate ΔG°rxn for each of the following reactions at at 25deg calcius

O2 2H2O 2Cu=4OH- 2Cu2

i got 23.1564kJ

Answer 1

I get the same thing you get, except DG0 should be negative.

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.