Van ’t Hoff equation

The Van ’t Hoff equation relates an equilibrium constant’s temperature dependence to the enthalpy change of a reaction. Its integrated form assumes the enthalpy change is approximately constant over the temperature range.

Chemical equilibrium: A state in which forward and reverse reactions occur at equal rates, leaving macroscopic composition constant. The equation describes how this state shifts when temperature changes.
Thermodynamic activity: A dimensionless effective concentration used to express chemical potential in nonideal systems. Equilibrium constants are defined using activities, even when concentrations approximate them.
Le Chatelier’s principle: A qualitative principle that predicts how an equilibrium responds to a change in conditions. The equation quantifies the temperature shifts that the principle predicts qualitatively.
Clausius–Clapeyron relation: A thermodynamic relation connecting phase-boundary pressure and temperature to latent heat. It links temperature to phase equilibrium pressure rather than a chemical reaction constant.
Equilibrium constant: A quantity expressing the relative activities of products and reactants at chemical equilibrium. It is the temperature-dependent quantity the equation predicts.
Chemical potential: The change in a system’s free energy when a component is added at fixed conditions. Equilibrium follows from equal chemical potentials across reacting species.
Calorimetry: The measurement of heat transferred during physical or chemical processes. Measured reaction enthalpies can predict equilibrium’s temperature dependence.
Arrhenius equation: An equation relating a reaction rate constant to temperature and activation energy. Its slope concerns activation energy, unlike the reaction enthalpy in this equation.
Reaction enthalpy: The heat absorbed or released in a reaction at constant pressure. Its sign and magnitude set the temperature response of the equilibrium constant.
Reaction quotient: The ratio of product and reactant activities evaluated at any composition. Comparing it with the equilibrium constant identifies the direction of net reaction.

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