S-I: In an aqueous solution the Van't hoff factor (i) of ${\mathrm{CH}}_3\mathrm{COOH}$ is $(1+\mathrm{\alpha })$

S-II: When dissolved in benzene $\left({\mathrm{C}}_6{\mathrm{H}}_6\right)$ the van't Hoff factor (i) of ${\mathrm{CH}}_3\mathrm{COOH}$ is $(1-\frac{\mathrm{\alpha }}{2})$

( $\mathrm{\alpha }$ - degree of dissociation / association)