Question

If $P_A^0$ and $P_B^0$ are 108 and 36 torr respectively. What will be the mole fraction of A in vapour phase if B has mole fraction 0.5 in the solution?

• A. 0.25
• B. 0.75
• C. 0.6
• D. 0.35

Answer 1

The correct option is B 0.75

In the solution, total pressure will be -

P = XA.p°A + XB.p°B

P = 0.5 × 108 + 0.5 × 36

P = 72 torr

Mole fraction of A in vapour phase -

XA' = XA.p°A / P

XA' = 0.5 × 108 / 72

XA' = 0.75

Therefore, mole fraction of A in vapour phase is 0.75