Question

In an ideal solution 1 mol of liquid A and 3 mole liquid B, total vapour pressure of solution is 500 mm of Hg. Vapour pressure of pure A is 200 mm of Hg and vapour pressure of pure B is x mm of Hg. Find the value of x and which is the least volatile compound

(1) 1800 A

(2) 600 A

(3) 900 B

(4) 500 B

Answer 1

Correct option is: (2) 600 A

\(500 = 200 \times \frac{1}{4} + \frac{3}{4} \times P^0 _ B\)

\(2000 = 200 + 3P^0 _B\)

\(3P^0 _ B = 1800\)

\(P^0 _B = 600 \ \text{mm of Hg}\)

B is more volatile