Electrode potential in ion transfer equilibrium

For a metal electrode at which a metal ion transfer reaction Mf = Mfi, is in equilibrium, as shown in Fig. 4-19, the metal ion level aM (M/s/v) in the electrode equals the hydrated metal ion level aM-(s/v) in the aqueous solution and the energy for the metal ion transfer across the electrode/solution interface equals zero (ciii-(M ) = 0). As shown in Fig. 4-20, then, we obtain Eqn. 4-22  

The electrode potential, i, in the equilibrium of metal ion transfer is thus derived from Eqns. 4-14 and 4-23 to obtain Eqn. 4-24  

Ionic electrode in equilibrium of metal ion transfer M = metal ion to transfer Pm = electrochemical potential of metal ions. 

follows that the electrode potential in equilibrium of metal ion transfer is given by the free enthalpy for the formation of a solid metal from both hydrated metal ions and standard gaseous electrons as shown in Eqn. 4—25  

Fermi level to or hypothetical Fermi level of the metal ion transfer equilibrium i.e. the Fermi level of hypothetical electrons equivalent to the metal ion level in the ion transfer equilibrium. 

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