Solutions – advanced and special cases - Nonideal mixtures
3 important questions on Solutions – advanced and special cases - Nonideal mixtures
Why can the gas phase, in general, be considered more often ideal than the liquid phase?
How is the partition coefficient and the relative volatility calculated for a non ideal vapor-liquid equilibrium?
All Ki and αi have a composition dependence.
Considering a binary system in which the vapor phase acts ideal and the exes Gibbs free energy of the liquid phase can be described according to:
what are K1 and K2?
To start with the expression of the total Gibbs free energy of the liquid is needed:
Then obtaining the chemical potential of species 1 in the liquid by taking the partial derivative of Gl:
Combining with the general non-ideal chemical potential expression:
Substituting the activity coefficient in the partition coefficient, and assuming that the fugacity coefficients are equal:
Integration to Nl2 results in:
Combining for the relative volatility:
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