Question:
The vapour pressure of acetone at $20^{\circ} \mathrm{C}$ is $185 \mathrm{torr}$. When $1.2 \mathrm{~g}$ of non-volatile substance was dissolved in $100 \mathrm{~g}$ of acetone at $20^{\circ} \mathrm{C}$, its vapour pressure was $183 \mathrm{torr}$. The molar mass ( $\mathrm{g} \mathrm{mol}^{-}$ 1) of the substance is :
Correct Option:
Solution:
