where Δ Δ r G is the Gibbs free energy of reaction under non-standard states at temperature T , Δ Δ r G ⊖ ⊖ is the Gibbs free energy for the reaction at ( T , P 0 ) , ξ ξ is the extent of reaction, and Q r is the thermodynamic reaction quotient. Since Δ Δ r G ⊖ ⊖ = − − R T ln ⁡ ⁡ K e q , the temperature dependence of both terms can be described by Van t'Hoff equations as a function of T. This finds applications in the field of electrochemistry. particularly in the study of the temperature dependence of voltaic cells.