Electrode Potentials Nernsts Law

We have seen (see Chap. 2) that electrode potential values are given by Nernst s law, which is legitimate only when no current flows through the electrodes. It calculates the cell potentials. 

The generalization of these equations is immediate. If we take into account the conventions on the activities, the preceding equations become 

The electrode potential is a function of the activities of the two members of the redox couple  

We must comment on Eq. (13.12). First, the standard potential (H+/H2) is, once and for all, conventionally chosen to be equal to zero, regardless of the temperature (see also Chap. 2). Second, due to the conventions about the activities and the ideal behavior of dihydrogen in usual conditions, we can set 

This is true in particular for Pm = 1 bar. When this is the case, we can write 

---