The standard free energy change of a process, ΔG°, was defined as the maximum work that could be performed by a system, Wmax. In the case of a redox reaction taking place within a galvanic cell under standard state conditions, essentially all the work is associated with transferring the electrons from reductant-to-oxidant, W_elec:

ΔG° = W_max  = W_elec

The work associated with transferring electrons determined by the total amount of charge (coulombs) transferred and the cell potential:

ΔG° = W_elec = −nFE_cell °

ΔG° = −nFE_cell °

Where n is the number of moles of electrons transferred, F is Faraday’s constant, and E°cell is the standard cell potential.

The relation between free energy change and standard cell potential confirms the sign conventions and spontaneity criteria previously discussed for both of these properties: spontaneous redox reactions exhibit positive potentials and negative free energy changes.