The van't Hoff factor of acetic acid in water will be (if completely ionised)

The ratio of the number of particles after attachment to the number of particles before association is known as the Van't Hoff factor.

$i=\frac{\text{ observed colligative property }}{\text{ Calculated Colligative property }}$

The number of ions produced from one molecule of a solute is equal to the van't Hoff factor for 100% dissociation of the solute.

For ${\mathrm{CH}}_3\mathrm{COOH}:$

${\mathrm{CH}}_3\mathrm{COOH}\to {\mathrm{H}}^{+}+{\mathrm{CH}}_3{\mathrm{COO}}^{-}$

After dissociation, the quantity of ions created $=1+1=2$

Consequently, the Van't Hoff factor $\mathrm{i}=2$.