Q.

Liquid A and B form an ideal solution. The vapour pressure of pure liquids A and B are 350 and 750 mm Hg respectively at the same temperature. If xA and xB are the mole fraction of A and B in solution while yA and yB are the mole fraction of A and B in vapour phase then:                    [2025]
 

1 xAxB<yAyB  
2 xAxB=yAyB  
3 xAxB>yAyB  
4 (xA-yA)<(xB-yB)  

Ans.

(3)

yAyB=PA°xAPB°xB

yAyB=350xA750xB

xAxB=750yA350yB

Thus xAxB>yAyB