The electrode potential of Hydrogen electrode depends upon the __________concentration, the pressure of ______________ and the temperature at which the electrode system is maintained. The electrode potential is independent of the surface area of the inert Platinum electrode.

H3O+1, diatomic Hydrogen gas H+1  ion has no independent existence. H+1ion combines with water to form H3O+1. Pure, dry diatomic Hydrogen gas has to be passed through the HCl aqueous solution to attain equilibrium. So, pressure of H2 gas decides the electrode potential. E=E0−2.303RT2Flog10PH2H3O+2 . The electrode potential is independent of the surface area of the electrodes.