Van't Hoff equation

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The Van't Hoff equation in chemical thermodynamics relates the change in temperature to the change in the equilibrium constant given the enthalpy change. The equation was first derived by Jacobus Henricus van 't Hoff.

[\ln \left( \right) = - \frac\left[ - fractest} right]]

In this equation [\ K_1] is the equilibrium constant at absolute temperature [\ T_1] and [\ K_2] is the equilibrium constant at absolute temperature [\ T_2]. [\ \Delta H^\circ ] is the enthalpy change and [\ R] is the gas constant.

In another notation:

[\ln \left( K \right) = - \frac\left[ start--end}right] + \frac ]

a plot of the reciprocal temperature versus the natural logarithm of the equilibrium constant measured for a certain equilibrium gives a straight line, the slope of which is the enthalpy change divided by the gas constant and the intercept of which is equal to the entropy change [\ \Delta S^\circ ] divided by the gas constant.

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