Question

$0.70g$ of an organic compound when dissolved in $32g$ of acetone produces an elevation of ${0.25}^{o}C$ in the boiling point. Calculate the molecular mass of organic compound ($K_b$ for acetone $=1.72K{mol}^{-1}$).

Answer 1

Given: Wt. of the solute $\left(w\right)=0.70g$
Wt. of the solvent $\left(W\right)=32g$
Elevation of boiling point $\left(\Delta T_b\right)={0.25}^{o}C$
$K_b=1.72Kkg{mol}^{-1}$
The relation of elevation of boiling point and molecular mass is:
$m=\frac{1000\times K_b\times w}{W\times \Delta T_b}=\frac{1000\times 1.72\times 0.70}{32\times 0.25}=150.5g$
Thus, the molecular mass of the organic compound is $150.5g$