Solubility of a solid nonelectrolyte

This section considers the solubility of a solid nonelectrolyte. For the solution process B(s) B(sln), the general expression for the thermodynamic equilibrium constant is K = aB(sln)/aB(s). The activity of the pure solid is a (s) = 7b(s). Let us use a solute standard state based on mole fraction then the solute activity is flB(sln) = Fx,b yx,B JCb- From these relations, the solubility expressed as a mole fraction is 

If we measure the solubility at the standard pressure, the pressure factors /b(s) and Fx b are unity and the solubility is given by 

If the pressure is not exactly equal to p°, but is not very much greater, the values of the pressure factors are close to unity and Eq. 12.5.6 is a good approximation. 

We can find the standard molar enthalpy of solution of B from the temperature dependence of the solubility. Combining Eqs. 12.1.12 and 12.5.6, we obtain 

The solubility may be small enough for us to be able to set the solute activity coefficient equal to 1, in which case Eq. 12.5.7 becomes 

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See also in sourсe #XX -- [ ]

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