$\Delta T_f=0-(-0.24^{\large\circ}C)=0.24^{\large\circ}C$
$M_2=\large\frac{1000K_f W_2}{\Delta T_f W_1}$
$\;\;\;\;\;\;=\large\frac{1000\times 1.86\times 0.5}{0.24\times 100}$
$\;\;\;\;\;\;=38.75gmol^{-1}$
Theoretical molar mass of KCl =39+35.5
$\Rightarrow 74.5gmol^{-1}$
$i=\large\frac{\text{Calculated mol mass}}{\text{Theoretical mol mass}}$
$\;\;\;=\large\frac{74.5}{38.75}$$=1.92$
$KCl \leftrightharpoons K^++Cl^-$
$1\;mole\quad 0\quad 0$
$1-\alpha\quad\; \alpha\quad\;\alpha$
Total number of moles after dissociation =$1+\alpha$
$i=\large\frac{1+\alpha}{1}$
$i-1=\alpha=1.92-1$
$\Rightarrow 0.92$
Percentage dissociation =92%