Question

Calculate the standard potential, E°, for this reaction from its equilibrium constant at 298 K. X(s) + Y^2+(aq) ⇌ X^2+(aq) + Y(s)     K= 1.43 x 10^-6     E^o = ? V

Answer 1

We know, for standard free energy change (ΔG^o)

ΔG^o = - 2.303 * R* T log K

and

ΔG^o = -nFE^o_cell

Hence, -nFE^o_cell = - 2.303 * R* T log K

E^o_cell = (2.303 * R* T log K)/ n*F

Where

K = 1.43 x 10^-6

R = 8.314 J K^-1 mol^-1

·         T = Temp in K = 298

·         n = moles of e^- from balanced redox reaction = 2 (for given reaction)

·         F = Faraday's constant = 96,485 C/mol

Hence, E^o_cell = (2.303 * 8.314 * 298 * log 1.43 x 10^-6)/ 2*96485

                                = (5705.848 * log 1.43 x 10^-6)/ 192970

                                = - 33348.8/ 192970

                                = - 0.17282 J/C

                E^o_cell = - 0.17282 J