In an electrochemical cell a redox reaction perform in two halves. Electrons are liberated by the oxidation half reaction at one electrode and go through an electrical circuit to another electrode where they are used for the reduction. The cell potential E is the potential difference between the two electrodes have to balance the thermodynamic tendency for reaction, so that the cell is in equilibrium and no electrical current flows. E is related to the molar Gibbs free energy change in the overall reaction according to

where n the number of moles of electrons passed per mole of reaction and F is the Faraday constant (9.6485×104 C mol-1).