Question

Boiling point of chloroform was raised by $0.323\, K$, when $0.5143\, g$ of anthracene was dissolved in $35\, g$ of chloroform. Molecular mass of anthracene is $\left(k_{f}\right.$ for $\left.C H C l_{3}=3.9\, K\, kg\,mol ^{-1}\right)$

• A. 79.42 g/mol
• B. 132.32 g/mol
• C. 177.42 g/mol
• D. 242.32 g/mol

Answer 1

Answer: (C)

Here, elevation in boiling point, $\Delta T_{b}=0.323\, K$
weight of anthracene, $w=0.5143\, g$
weight of chloroform $W=35\, g$
molal elevation constant $k_{b}=3.9\, K\,kg / mol$
$m=\frac{k_{b} \times w \times 1000}{W \times \Delta T_{b}}$
$=\frac{3.9 \times 0.5143 \times 1000}{0.323 \times 35}$
$=177.42\, g / mol$