Explanation:
Given, $\mathrm{i}=1.98$, Concentration $=0.01 \mathrm{M}$
The dissociation of $\mathrm{BaCl}_{2}$ is-
$\mathrm{BaCl}_{2} \rightleftharpoons \quad \mathrm{Ba}^{2+}+2 \mathrm{Cl}^{-}$
We know that-
$\alpha=\frac{\mathrm{i}-1}{\mathrm{n}-1}$
Where, $i=$ van't Hoff factor
$\begin{aligned}
\mathrm{n} & =\text { number of dissociated ion } \\
\alpha \quad \alpha & =\frac{1.98-1}{3-1} \\
\alpha & =\frac{0.98}{2} \\
\alpha & =0.49
\end{aligned}$
$\therefore \%$ dissociation $=\alpha=100=49 \%$