Standard electrode potential to produce an electric potential, Gibbs free energy Δ"G"° must be negative, in accordance with the following equation: where "n" is number of moles of electrons per mole of products and "F" is the Faraday constant, ~96485 C/mol. As such, the following rules apply: Thus in order to have a spontaneous reaction (ΔG° < 0), "E"° must be positive, where: where "E"° is the standard potential at the anode and "E"° is the standard potential at the cathode as given in the table of standard electrode potential. Standard electrode potential In electrochemistry, it is defined as the measure of the
Electrode potential that only the magnitude expressed according to the convention (2) be called "the electrode potential". To avoid possible ambiguities, the electrode potential thus defined can also be referred to as "Gibbs–Stockholm electrode potential". In both conventions, the standard hydrogen electrode is defined to have a potential of 0 V. Both conventions also agree on the sign of "E" for a half-cell reaction when it is written as a reduction. The main difference between the two conventions is that upon reversing the direction of a half-cell reaction "as written", according to convention (1) the sign of "E" also switches, whereas in