Question

To the nearest tenths, what is the value of ΔG°′ (in kcal/mol) for the overall spontaneous reaction that would result given the following two half reactions?

Aox + 2H+ + 2e- → Ared E°′ = -0.3

Box + 2H+ + 2e- → Bred E°′ = -0.18

Answer 1

for spontaneous reaction Eocell should be positive and ΔG° should be negative

to get Eocell psotive

Eocell = higher potential - lower potential

            = -0.18 + 0.3

       = 0.12 V

ΔG° = - n F Eo

        = -2 x 96500 x 0.12 x 10^-3

      = - 23.2 kJ / mol (divide by 4.184 to convert into calories)

       = -5.5 kcal / mol

ΔG° = - 5.5 kcal / mol