Fundamentals of Chemical Engineering Thermodynamics

Chapter 11. Ideal Solution

In the previous chapter we developed the general criteria for phase equilibrium and showed how the phase diagram and all other properties of a mixture can be calculated if the equation of state is known. In all property calculations that are based on equations of state we are starting from the ideal-gas state and use the equation of state to calculate residual properties, in effect, to extrapolate from the ideal gas to the actual state of the system. This approach works quite well for mixtures of nonpolar molecules whose interactions are captured accurately by cubic equations of state. Mixtures of strongly interacting molecules cannot be described by these methods with sufficient accuracy.¹ A different approach is needed ...