Gibbs Free Energy and Phase Separation: Example Problems

Try to solve these problems before watching the solutions in the screencasts.

Example Problem 1

Calculate ΔG for a binary liquid mixture at 75°C that has a mole fraction of 0.30 for component 1 (x_{1}). The vapor in equilibrium with the liquid has a pressure of 0.31 bar and a mole fraction of 0.65 for component 1 (y_{1}). The saturation pressures are: P_{1}^{sat} = 0.33 bar; P_{2}^{sat} = 0.10 bar.

Example Problem 2

Suppose the excess Gibbs free energy is fit by the equation:

G^{E} = x_{1}x_{2}RT(Ax_{1} + Bx_{2}), where A = 2.3 and B = 2.7

Does this liquid mixture exhibit phase separation? If so, over what composition range?