Gibbs and Helmholtz Energies

Abstract

Some properties of the Gibbs and Helmholtz energies, two thermodynamic functions of utmost importance in chemistry especially for the study of the notion of activity, are recalled. The chemical potential of a species in a system, which is the pivotal notion of the chemical reactivity (most of the time entailing the notion of activity), is, indeed, a particular Gibbs energy. Hence, for example, the changes in Gibbs and Helmholtz energies accompanying a process provide us with an equilibrium criterion, at least in some experimental conditions.

In a first time, a brief recall of some properties of the entropy function is mentioned in order to grasp the significance of these two functions. Later in the chapter, for additional information, some notions concerning potential functions are also given.