Raoult's Law: Binary Liquid-Vapor Phase Diagrams: A Simple Physical Chemistry Experiment

Abstract

A new physical chemistry laboratory experiment illustrating Raoult's law behavior of ideal solutions is described. The vapor composition of binary mixtures of a ketone and an aromatic solvent is measured spectrophotometrically and the results used to generate Raoult's law vapor pressure plots and binary liquid-vapor phase diagrams. The method is more straightforward and experimentally easier to carry out than the traditional distillation techniques. Student results are presented for ortho-xylene/acetone and ortho-xylene/methyl isobutyl ketone mixtures. Both of these solutions show slight positive deviations from Raoult's law. The results are discussed in terms of the intermolecular interactions occurring in the mixtures.