Two volatile liquids ‘A’ and ‘B’ are mixed in the mole ratio 3 : 1. Vapour pressure of pure liquid ‘A’ is 200 mmHg and pure liquid ‘B’ is 600 mmHg. Mole fraction of ‘B’ in vapour phase will be

GivennA:nB=3 : 1 XA=34; XB=14; Applying Raoult's law pA=pA0XA;pB=pB0XB pA=20034=150 mmHg pB=60014=150 mmHg ptotal=pA+pB=300 mmHg Applying Dalton's law in vapour phase pB=ptotalyByB=M.F. of 'B' in vapour phase yB=150300=0.5