Exergonic reaction

An exergonic reaction is a chemical reaction where the change in the Gibbs free energy is negative, indicating a spontaneous reaction. Symbolically, the release of Gibbs free energy, G, in an exergonic reaction is denoted as


 * $$\Delta G=G_{\rm{products}}-G_{\rm{reactants}}<0.\,$$

Although exergonic reactions are said to occur spontaneously, this does not imply that the reaction will take place at an observable rate. For instance, the disproportionation of hydrogen peroxide is very slow in the absence of a suitable catalyst. It has been suggested that eager would be a more intuitive term in this context.

More generally, the terms exergonic and endergonic relate to the Gibbs free energy change in any process, not just chemical reactions. An example of an exergonic reaction is cellular respiration.

The terms exothermic and endothermic reactions relate to the enthalpy change of a process.