Solid Volumes Not Considered Constant

The assumption that the volumes of the solid phases are constant is not always acceptable. For example, in reactions involving only solids, both A V and Aj-S will be small, and because these represent the slope of A G versus P and T, small errors in 

This is considerably simplified by letting Pr = 1. Integrating and collecting terms then results in 

We remind the reader at this point that all the expressions involving a, b, and c in this chapter are derived using the Maier-Kelley expression for the variation of Cp as a function of T. Several other equations are in common use, which will of course change the derived equations. Obviously we cannot derive all the equations for each case the important thing is to see the dependence of the various functions discussed here on the heat capacity. In Appendix B we present the essential equations for several versions of the heat capacity expression. 

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