Calculating K from E°cell

Calculating an equilibrium constant from a standard cell potential means combining ΔG° = −nFE°cell and ΔG° = −RT ln K into ln K = nFE°cell/RT, then solving for K by exponentiating both sides.

For a two-electron reaction with E°cell = 0.463 V at 298 K, ln K = (2)(96,485)(0.463)/[(8.314)(298)] ≈ 36.0, so K ≈ 4.3 × 10¹⁵, an extremely large constant consistent with the strongly favorable, decisively spontaneous potential this cell already reports. The same K could equally be reached through ΔG° first (Chem 2133), the two routes agreeing since both trace back to one electron-transfer reaction.