begin mathsize 36px style log open parentheses K subscript 1 over K subscript 2 close parentheses space equals fraction numerator negative increment H to the power of O over denominator R end fraction open parentheses 1 over T subscript 2 minus 1 over T subscript 1 close parentheses end style

K1The equilibrium constant at absolute temperature T1 ; K2=The equilibrium constant at absolute temperature T2 ;
The standard enthalpy change ; T& T2 = Temperature; R= Gas constant






Equilibrium constant of a reaction is related to the temperature of the system. By Van't Hoff equation the change is in equilibrium is associated to the change in standard enthalpy. On the contrary, one can calculate the standard enthalpy change of a reaction by recording two equilibrium constant of the reaction at two different temperatures. Van't Hoff equation assumes that the standard enthalpy change is constant over the temperature range. In reality, this equation serves as a very good approximation.            

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