text: The Van 't Hoff isotherm can be used to determine the temperature dependence of the Gibbs free energy of reaction for non-standard state reactions at a constant temperature:
  where  is the Gibbs free energy of reaction under non-standard states at temperature ,  is the Gibbs free energy for the reaction at ,  is the extent of reaction, and  is the thermodynamic reaction quotient. Since , the temperature dependence of both terms can be described by Van tHoff 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.
  The isotherm can also be used at fixed temperature to describe the Law of Mass Action. When a reaction is at equilibrium,  and . Otherwise, the Van 't Hoff isotherm predicts the direction that the system must shift in order to achieve equilibrium; when , the reaction moves in the forward direction, whereas when , the reaction moves in the backwards direction. See Chemical equilibrium.