The freezing point of a solution containing 0.2g of acetic acid is 20.0g of benzene is lowered by $0.45^{\large\circ}$C. Calculate the molar mass of acetic acid from this data?[For benzene,$K_f=5.12Kkg mol^{-1}]$

Question

$\begin{array}{1 1}113.77g mol^{-1}\\170g mol^{-1}\\180g mol^{-1}\\190g mol^{-1}\end{array} $

Answer 1

Given :

$W_1=20.2g$

$W_2=0.2g$

$\Delta T_f=0.45^{\large\circ}C$

$K_f=5.12Kkg mol^{-1}$

Molar mass of acetic acid $M_2=\large\frac{K_f \times W_2\times 1000}{\Delta T_f\times W_1}$

$\Rightarrow \large\frac{5.12\times 0.2 \times 1000}{0.45\times 20.0}$

$\Rightarrow 113.77gmol^{-1}$