Variation of Free Energy with Temperature

In all metallurgical processing, heterogeneous reactions and the approach to equilibrium between two or more phases are of great importance. Much of the information on equilibrium is contained in the equilibrium constant which, as mentioned earlier, is related to the standard free energy change by the equation 

The change, AG°, in the standard free energy with temperature is due to the changes with temperature of AH0 and AS0, and, of course, to the change in the temperature itself. Both AH° and AS0 change with temperature if the total heat capacity of the reactants is not the same as that of the products. In view of the expressions, given earlier, regarding the variation of AH0 and AS0 with temperature, the above equation can be written as T T AC 

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Equation (18) represents the variation of free energy with temperature. 

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