The Electrode Potential

Abstract

“Electrode potential” is certainly the most used term in electrochemistry, and is very likely to be one of the most popular in the entire field of chemistry. Sound knowledge of the physical and chemical phenomena involved in the establishment of electrode potentials does not correspond, however, to the very wide use of the term. None would be surprised by a 0.059-V change in potential of a hydrogen electrode as the activity of H+ in solution is changed by a power of ten, but it would certainly be surprising if everyone knowing this were actually able to give a physical description of what is occurring at the electrode as the concentration of H+ is changed and why the electrode potential changes. Further, when the term “electrode potential” is used, it generally refers to the potential as experimentally measured with respect to a given reference electrode. Conceptually, however, no reference electrode must necessarily be involved for an “electrode potential” to be defined. It follows that the physical meaning behind the same term “electrode potential” is quite different in the two cases. This is certainly not as well recognized as the term itself is.