At 80∘C the vapour pressure of pure liquid ‘A’ is 520 mm Hg and that of pure liq ‘B’ is 1000 mm Hg. If a mixture of both the liquids form an ideal solution which boils at 80∘C and 1 atm pressure, the mole fraction of ‘A’ in the liquid mixture is:
P∘AXA+P∘BXB=Pmix(520)XA+(1000)(1−XA)=760520XA−1000XA=760−1000−480XA=−240∴XA=12=0.5