Standard Gibbs Energy Change

The standard Gibbs energy change is defined as the change in Gibbs energy for the process in which the reactants in their standard states are converted into the products in their standard states. It is denoted by the symbol Δ_rG°.

The standard Gibbs energy of formation of a compound is defined as the change in Gibbs energy when 1 mole of the compound is formed from its constituent elements in their standard states. Like the standard enthalpy of formation of an element, the standard Gibbs energy of formation of an element in its standard state is taken as zero.

The standard Gibbs energy change (Δ_rG°) is related to the equilibrium constant (K) of the reaction by the expression:

Δ_rG^o = – RT ln K = – 2.303 RT log K