Effect of charges on reactions in solution

The following does not include the effect of solvation and the change in the structure of the solvent on activation. This is discussed independently in Section 7.4.9. 

For ideal conditions, corresponding to rate constants extrapolated to zero ionic strength, 

Since reactions should be compared under ideal conditions, equation (7.26) is used. The effect of temperature on A G allows A S to be found, since 

However, for reactions in solution it is necessary to consider also the fact that the relative permittivity eT decreases as temperature increases. Thus, for ions of like charge (z.kZ.k positive), the electrostatic term in Equation (7.26) increases as T increases. This gives a positive contribution to (d AG /dT)p, and therefore a negative contribution to A S. Consequently, A S is predicted to be less than the value it would have taken if there had been no electrostatic term. 

From such arguments it can be shown that Equation (7.26) gives the following relations. 

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