Question

Write Raoult's law of relative lowering of vapour pressure.

Hint:

Raoult's law explains the lowering of vapour pressure in solutions based on the mole fraction of the solute.

Answer 1

Step 1: Raoult’s Law.
Raoult's law states that the relative lowering of the vapour pressure of a solvent in a solution is equal to the mole fraction of the solute in the solution. \[ \frac{\Delta P}{P_0} = X_{\text{solute}} \] where:
- \( \Delta P \) is the lowering of vapour pressure,
- \( P_0 \) is the vapour pressure of the pure solvent,
- \( X_{\text{solute}} \) is the mole fraction of the solute.
Step 2: Explanation.
This law is valid for ideal solutions where there is no significant interaction between the solute and solvent molecules. It shows that as the amount of solute increases, the vapour pressure of the solvent decreases.