Question

A mixture of two liquids A and B have vapour pressures 3.4 × 10⁴ Mn^-2 and 5.2 × 10⁴ Nm^-2. If the mole fraction of A is 0.85, find the vapour pressure of the solution.

Answer 1

Given: Vapour pressure of pure liquid `A = P_A^0`

= 3.4 × 10⁴ Nm^-2

Vapour pressure of pure liquid `B = P_B^0`

= 5.2 × 10⁴ Nm^-2

Mole fraction of A = x_A = 0.85

Mole fraction of B = x_B = 1 - X_A

= 1 - 0.85 = 0.15

The vapour solution is given by

`P_(soln) = X_A P_A^0 + X_B P_B^0`

= 0.85 × 3.4 × 10 + 0.15 × 5.2 × 10⁴

= 2.89 × 10⁴ + 0.78 × 10⁴

= (2.89 + 0.78) × 10⁴

P_soln = 3.67 × 10₄ Nm^-2