Chemistry - Liquid Solution Question with Solution | TestHub

Depression in freezing point or elevation in melting point depends upon the number of solute particles rather than the kind of solute particles. 

Depression in freezing point (${\mathrm{\Delta T}}_{\mathrm{f}}$) is directly proportional to number of solute particles.

Also, ${\mathrm{\Delta T}}_{\mathrm{f}}$ is directly proportional to molality.

${\mathrm{\Delta T}}_{\mathrm{f}}=\mathrm{m}\times {\mathrm{k}}_{\mathrm{f}}$

Amongst the given options acetic acid has lowest molecular mass.

The molar mass of acetic acid is $60.05$ g mol^-1.

Hence if the molecular mass is less, molality will be more, so the lowest freezing point will be shown by $180$gm of acetic acid in $1$L aqueous solution.