Abnormal Molecular Mass

$19.5 \mathrm{g}$ of ${\mathrm{CH}}_2\mathrm{FCOOH}$ is dissolved in $500 \mathrm{g}$ of water. The depression in the freezing point of water observed is $1.0^{°}\mathrm{C}$. Calculate the Van't Hoff factor and dissociation constant of ${\mathrm{CH}}_2\mathrm{FCOOH}$. (${\mathrm{K}}_{\mathrm{f}}=1.86 \mathrm{K} \mathrm{kg} {\mathrm{mol}}^{-1}$)

A $5\%$ solution of ${\mathrm{CaCl}}_2$ at $0°\mathrm{C}$ developed an osmotic pressure of $15$ atmosphere. Calculate the degree of dissociation.

What is van't Hoff's factor? How is it related to the degree of association of a solute with solvent?