The van’t Hoff factor for 0.1M $\mathrm{Ba}{\left({\mathrm{NO}}_3\right)}_2$ solution is 2.74. The degree of dissociation is

$\mathrm{Ba}\left({\mathrm{NO}}_3\right)\rightleftharpoons {\mathrm{Ba}}^{+2}+2{\mathrm{NO}}_3^{-}$

$\text{ At }\mathrm{t}=00.1\mathrm{M}00$

$\text{ At eqm. (0.1-x)M }\text{ xM }2\times \mathrm{M}$

$\mathrm{i}=\frac{(0.1-\mathrm{x})+\mathrm{x}+2\mathrm{x}}{0.1}\Rightarrow 2.74=\frac{0.1+2\mathrm{x}}{0.1}$

$0.1+2x=0.274\Rightarrow 2x=0.274-0.1=0.174$

$\Rightarrow x=\frac{0.174}{2}=0.087$

$\therefore \text{ Degree of dissociation }=\frac{0.087}{0.1}\times 100=87\mathrm{\%}$