Two volatile liquids A and B are mixed in the mole ratio 3 : 2 to form an ideal solution. Vapour pressure of pure liquids A and B is 600 mm Hg and 300 mm Hg respectively. Mole fraction of B in vapour phase is

Mole fraction in liquid mixtureXA=35 ; XB=25Given  pAo=600 mm ;   pBo=300 mmAccording to Raoult's law Ptotal=pAoXA+pBoXBPtotal=60035+30025Ptotal=360+120mmIn vapour phase, applying Dalton's lawpB=ptotal×yByB=pBptotalyB=120480yB=0.25