Heterogeneous (Multiphase) Mixtures
R. Ravi · 2020
This chapter extends the criteria of equilibrium to mixtures to establish the uniformity of temperature, pressure and chemical potential of each of the components as a necessary condition for a mixture at equilibrium. It expresses the criteria of equilibrium in terms of the fugacities thereby facilitating discussion of phase equilibrium calculations. The chapter studies the applications of the phase rule in a qualitative manner focusing on the choice of variables and representation in terms of phase diagrams. A detailed study of phase equilibrium calculations is undertaken within the context of vapor-liquid equilibrium. First the ideal case is considered where the vapor phase is treated as an ideal gas mixture and the liquid phase approximated as an ideal solution. Next, non-ideality in the liquid phase is introduced through activity coefficient models. Finally non-ideality in the vapor phase is treated using fugacity coefficients.