text: If both the equilibrium constant,  and the standard enthalpy change, , for a reaction have been determined experimentally, the standard entropy change for the reaction is easily derived. Since  and 
  To a first approximation the standard enthalpy change is independent of temperature. Using this approximation, definite integration of the van 't Hoff equation 
  gives
  This equation can be used to calculate the value of log K at a temperature, T, knowing the value at temperature T.
  The van t Hoff equation also shows that, for an exothermic reaction (), when temperature increases K decreases  and when temperature decreases K increases, in accordance with Le Chateliers principle. The reverse applies when the reaction is endothermic.
  When K has been determined at more than two temperatures, a straight line fitting procedure may be applied to a plot of  against  to obtain a value for . Error propagation theory can be used to show that, with this procedure, the error on the calculated  value is much greater than the error on individual log K values. Consequently, K needs to be determined to high precision when using this method. For example, with a silver ion-selective electrode each log K value was determined with a precision of ca. 0.001 and the method was applied successfully.
  Standard thermodynamic arguments can be used to show that, more generally, enthalpy will change with temperature.
  where C is the heat capacity at constant pressure.