2 moles each of liquid a and b ate dissolved to form an ideal somution

1.	2 moles each of liquid a and b ate dissolved to form an ideal somution. What will be the mole fraction of b in vapoir state
Answer» ANSWER: We know that, mole fraction can be calculated USING the following formula: $P_{<klux>B</klux>} =P_{T} *X_{B}$ Here $P_{B}$ is partial pressure of B=100 mm Hg as in the vapor phase the partial pressure of B will be EQUAL to its vapor pressure in pure state. And $P_{T}$ =(100+200)mm of Hg so we get $X_{B} =P_{B} /P_{T}$ =200/300 =2/3