Question

The exact mathematical expression of Raoult's law is :

• A. $\frac{P_0-P_s}{P_0}=\frac{n}{N}$
• B. $\frac{P_0-P_s}{P_0}=\frac{N}{n}$
• C. $\frac{P_0-P_s}{P_s}=\frac{n}{N}$
• D. $\frac{P_0-P_s}{P_0}=n\times N$

Answer 1

The correct option is A $\frac{P_0-P_s}{P_0}=\frac{n}{N}$

The expression for the Raoult's law is : $\frac{P_0-P_s}{P_0}=\frac{n}{n+N}=x$

where,

$P_0=$ Pressure of the pure solvent.

$P_s=$ Pressure of the solution.

$n$ and $N$ are the moles of solute and solvent respectively.

For very dilute solutions, $n<<N$

So, $n+N\approx N.$

Thus, the expression becomes $\frac{P_0-P_s}{P_0}=\frac{n}{N}$

Option A is correct.