Standard Gibbs Free Energy Change

**Semantic type:** Quantitative Concept

**Definition:** A measure of the spontaneity of a chemical reaction. It is the change in the free energy of a system during a chemical reaction at a pH of 7.0. It is equal to the change in the enthalpy of the system minus the change in the product of the temperature times the entropy of the system. The resulting sign of Delta G determines if a reaction is spontaneous or not: DG < 0 indicates that the reaction is spontaneous; DG > 0 indicates that the reaction is not spontaneous; and DG = 0 indicates that the reaction is at equilibrium.

**Synonyms:** - Delta G Prime 0 - Delta G Prime Zero - standard gibbs free energy change