Azeotropes: Example Problems

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

Example Problem 1

A binary system is in vapor-liquid equilibrium at 80.°C and 0.28-bar pressure, and x1 = 0.20, y1 = 0.54. At 80°C, P1sat = 0.35 bar, P2sat = 0.15 bar. Does this system possess an azeotrope at 80°C? If yes, what is its composition? If no, show why not. Assume the liquid phase obeys a simplified form of the Margules equation: GE = Bx1x2RT

Example Problem 2

The bubble pressure for a non-ideal binary liquid (x1 = 0.35) is 1.479 bar at 42°C. The mole fraction of the vapor in equilibrium with the liquid (y1) is 0.578. The liquid can be modelled by the one-parameter Margules equation. The saturation pressures are P1sat = 1.3 bar and P2sat = 0.80 bar. What is the bubble pressure at 42°C when x1 = 0.85? What is the mole fraction of the gas phase in equilibrium with the liquid?