1 mol benzene (P°benzene = 42 mm) and 2 mol toluene (P°toulene = 36 mm) will have
Total vapour pressure of 38 mm.
Mole fraction of vapour of benzene above liquid mixture is 7/19
Positive deviation from Raoult's law.
Negative deviation from Raoult's law.
Benzene and toluene⇒ Ideal solution.
PTotal=P°AXA+P°BXB=42×13+36×23=38 mm Hg XVBenzene=PBenzenePTotal=42×1338=719