Question

Discuss Raoult's law of realtive lowering of vapour pressure.

Answer 1

Raoults, in 1886, established a relationship between relative lowering in vapour pressure and composition of the solution after a series experiments in various solvents. The relationship is known as Raoult's Law.

It states that the relative lowering in vapour pressure of a dilute solution is equal to the mole fraction of the solute present in the solution. 

If n moles of solute be dissolved in N moles of the solvent, the mole fraction of the solute will be $\frac{n}{n+N}$,

A/c to Raoult's law

$\frac{P_0-P_S}{P_0}=\frac{n}{n+N}$

This is marhematical expression of Raoult's law.