Question

$20g$ of a substance is dissolved in $500mL$ of water and the osmotic pressure of the solution is found to be $600mm$ of mercury at ${15}^{\circ }C$. The molecular weight of substance is:

• A. $998$
• B. $1028$
• C. $1098$
• D. $1198$

Answer 1

The correct option is D $1198$

$\pi V=nRT$

$\frac{500}{1000}\times \pi =\frac{20}{M}\times 0.082\times (273+15)$

$\frac{500}{1000}\times \frac{600}{760}=\frac{20}{M}\times 0.082\times 288$

$M=\frac{20\times 0.082\times 288\times 1000\times 760}{500\times 600}=1198g$

Hence, the correct option is $D$