The Van't Hoff factor $i$ for a $0.2$ molal aqueous solution of $\mathrm{HCN}$ whose degree of dissociation is $0.5$ is :

Which one of the following is the expression of Raoult's law?

$\mathrm{p}=$vapour pressure of pure solvent

${\mathrm{p}}_{\mathrm{s}}=$vapour pressure of the solution

$\mathrm{n}=$number of moles of the solute

$\mathrm{N}=$number of moles of the solvent

Consider the following solutions in water.

(I) $1\mathrm{M}$ Sucrose

(II) $1\mathrm{M} \mathrm{KCl}$

(III) $1\mathrm{M}$ Benzoic acid

(IV) $1\mathrm{M}{\left({\mathrm{NH}}_4\right)}_3{\mathrm{PO}}_4$

Which of the following is/are true?