Electrical work done in one second is equal to electrical potential multiplied by total charge passed. If we want to obtain maximum work from a galvanic cell then charge has to be passed reversibly. The reversible work done by a galvanic cell is equal to decrease in its Gibbs energy and therefore, if the EMF of the cell is E and nF is the amount of charge passed and ∆rG is the Gibbs energy of the reaction, then
∆rG = – nFEcell
It may be remembered that Ecell is an intensive parameter but ∆rG is an extensive thermodynamic property and the value depends on n. From the measurement of Eocell , we can obtain an important thermodynamic quantity, ∆rGo , standard Gibbs energy of the reaction. | 
