Question

At 300 K, the vapour pressure of liquids A and B are 600 and 500 mm of Hg respectively. Two moles of A and three moles of B are mixed. The mole fractions of A and B in vapor state are respectively

• A. 0.4, 0.6
• B. 0.7, 0.3
• C. 0.444, 0.555
• D. 0.666, 0.3

Hint:

The mole fractions in the vapor phase depend on the relative vapor pressures of the components.

Answer 1

The Correct Option is C

Step 1: The mole fraction of A in the vapor phase is given by: \[ \text{Mole fraction of A in vapor phase} = \frac{P_A}{P_A + P_B} = \frac{600}{600 + 500} = \frac{600}{1100} = 0.545 \] Step 2: The mole fraction of B in the vapor phase is given by: \[ \text{Mole fraction of B in vapor phase} = \frac{P_B}{P_A + P_B} = \frac{500}{600 + 500} = \frac{500}{1100} = 0.454 \] Step 3: The correct values for mole fractions are: Mole fraction of A = 0.444, Mole fraction of B = 0.555