HW #5, WB.2 - Determination of Azeotropes Using Margules and van Laar Equations - 12 pts

For each of the following systems, determine the azeotropic pressure and composition.

a.) Benzene(1) / acetonitrile(2) at 40oC. Margules parameters: A12 = 1.780, A21 = 1.055. Vapor pressures at 40oC: P1* = 29.82 kPa, P2* = 22.78 kPa.
Ans.: P ≈ 37 kPa

b.) Acetone(1) / chloroform(2) at 50oC. van Laar parameters: L12 = -0.936, L21 = -0.678. Vapor pressures at 50oC: P1* = 81.75 kPa, P2* = 69.38 kPa.
Ans.: P ≈ 61 kPa

Hints :
How can you recognize when an azeotrope exists ? Express this idea in terms of the Modified raoult's law and the Margules and van Laar Equations.