Question

Vapour pressure of pure liquid A is 200 mm Hg. If 1 mol of A and 3 mol of B are mixed. Assuming solution to be ideal, find the vapour pressure of pure liquid ‘B’, if total vapour pressure of solution is 500 mm Hg

Answer 1

For an ideal solution \(P_S = P _{A} ^{\circ} X_A + P_B ^{\circ} X_B\)

\(X_A = \frac{1}{4}\)

\(X_B = \frac{3}{4}\)

\(500 = 200 \times \frac{1}{4} + P _{B}^{\circ} \times \frac{3}{4}\)

\(P_B^{\circ} \times \frac{3}{4} = 450\)

\(P_{B}^{\circ} = \frac{450 \times 4}{3} = 600\ mm Hg\)