Equilibrium Thermodynamics of Reacting Multiphase Mixtures

It is expected that entirely new options for thermodynamic modeling of simultaneous chemical and phase equilibrium will become available from molecular simulations techniques. Such methods are beginning to become available [12, 13], but can not be covered in the scope of the present chapter. 

The conditions for simultaneous phase and chemical equilibrium at constant temperature T and pressure p derived from the second law of thermodynamics are well known and are given here for a system of N components i, P phases j, in which R chemical reactions r occur. 

For practical purposes, working equations have to be derived from the fundamental relations (4.2) and (4.3) by using appropriate normalizations of the chemical potential. Which working equation is appropriate will depend on the application. Some popular choices for the normalization of the chemical potential are as follows. 

Relations similar to equation (4.6) are used for electrolytes (A+) (B )v- iii solution 

Note that, in principle, there is a free choice to apply any of the equations (4.4)—(4.8) to any component in any phase. The only condition that has to be fulfilled is the Gibbs-Duhem equation for each phase, which reads at constant temperature and pressure 

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