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
Standard electrode potential 0.00 V and any electrode, for which the electrode potential is not yet known, can be paired with SHE—to form a galvanic cell—and the galvanic cell potential gives the unknown electrode's potential. Using this process, any electrode with an unknown potential can be paired with either the SHE or another electrode for which the potential has already been derived and that unknown value can be established. Since the electrode potentials are conventionally defined as reduction potentials, the sign of the potential for the metal electrode being oxidized must be reversed when calculating the overall cell potential. Note that the electrode