Activity coefficients and thermodynamic excess functions

We shall now show how the activity coefficients and thermodynamic excess functions can be evaluated explicitly in a particularly simple case, namely that in which the only complexes formed are the double molecules AB. A solution which appears to correspond to this case is the mixture acetone-f chloroform. 

Substituting these equations in (26.12), and setting both and x% equal to unity, 

In these equations hrp j = dHld )T is the heat of reaction corresponding to the equilibrium governed by the constant K (cf. 7.37). 

In fig. 26.8 equation (26.68) is compared with the experimental data for the system acetone + chloroform. The full line is calculated 

Here again we find good agreement on putting the heat of dissociation of the complex equal to - 2700 cal./mole. 

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