A solution has 1:4 molar ratio of pentane and hexane. The vapour pressure of pure hydrocarbons at 20ºC are 440 mm Hg for pentane and 120 mm of Hg for hexane. The mole fraction of pentane in vapour phase would be

mole ratio of Pentane to hexane in liquid mixture = 1:4XA &  XB  are molefractions in liquid phaseAccording to Raoult's law,                 = (88+96)mm =184gIn vapour phase ,                          According to Dalton's law                    YA & YB are the mole fractions of A & B in vapour phase