Introductory Chemical Engineering Thermodynamics

Unit III: Fluid Phase Equilibria in Mixtures

We have already encountered the phase equilibrium problem in our discussions of pure fluids. In Unit I, we were concerned with the quality of the steam. In Unit II, we developed generalized relations for the vapor pressure. These analyses enable us to estimate both the conditions when a liquid/vapor phase transition occurs and the ratio of vapor to liquid. In Unit III, we are not only concerned with the ratio of vapor to liquid, but also with the ratio of each component in the liquid to that in the vapor. These ratios may not be the same because all components are not equally soluble in all phases. These issues arise in a number of applications (e.g., distillation or extraction) that are extremely ...