Question

The freezing point of a solution containing $0.2g$ of acetic acid in $20g$ of benzene is lowered by $0.{45}^{o}C$ Calculate the degree of association of acetic acid in benzene ($K_f$ for benzene is $5.12K$ kg ${mol}^{-1}$).

Answer 1

$\Delta T_f=i{k}_{f}m$

$\Rightarrow 0.45=i\times 5.12\times \frac{\frac{0.2}{60}}{20}\times 1000$

$\Rightarrow i=\frac{0.95}{5.12}\times \frac{60}{0.2}\times \frac{20}{1000}=0.527$

$2C{H}_{3}COOH\rightleftharpoons (C{H}_{3}COOH{)}_2$

$1-\alpha$ $a/2$

$\therefore i=1+\frac{\alpha }{2}=0.527$

$\Rightarrow \alpha =0.946$ Answer.