Q. Which of the following is the expression of Raoult’s law? ($p =$vapour pressure of pure solvent, $p_{s} =$vapour pressure of the solution)
A) $\frac{p - p_{s}}{p} = \frac{n}{n + N}$
B) $\frac{p_{s} - p}{p} = \frac{N}{N + n}$
C) $\frac{p - p_{s}}{p_{s}} = \frac{N}{N - n}$
D) $\frac{p_{s} - p}{p_{s}} = \frac{N - n}{N}$
Explanation
(a)
According to Raoult’s law, for non volatile solute, the relative lowering of vapour pressure of a solution is equal to the mole fraction of the solute
$\frac{p - p_{s}}{p} = \frac{n}{n + N}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.