Question

if mole fraction of a non water volatile solute in Benzene is 0.2 then the vapour pressure of this solution will be given that vapour pressure of pure benzene is 500 mm of HG​

Answer 1

Given:

Mole fraction of solute, Xa = 0.2

Vapour pressure of pure benzene, P° = 500 mm Hg

To Find:

The vapour pressure of the solution.

Calculation:

- Mole fraction of benzene, Xb = 1 - Xa

⇒ Xb = 1 - 0.2

⇒ Xb = 0.8

- As the solute is non volatile, so it does not have any vapour pressure.

- Thus, the vapour pressure of the solution, P = P° × Xb

⇒ P = 500 × 0.8

⇒ P = 400 mm Hg

- So the vapour pressure of the solution is 400 mm Hg.