Question

Explain how benzene in toluene obeys Raoult’s law.

Answer 1

The variation of vapour pressure of pure benzene and toluenc with its mole fraction is given in the graph. 

1. The vapour pressure of pure toluene and pure benzene are 22.3 and 74.7 mm Hg respectively.

2. The graph shows the partial vapour pressure of pure components increases linearly with the increase of the mole fraction of the respective components. The total pressure at any composition of the solute and solvent is given by the straight line.

3. P_solution = P⁰_toluene + x_benzene (P⁰_benzene – P⁰_toluene)