(a) Define molal depression constant. How is it related to enthalpy of fusion?

Molal depression constant is the depression in freezing point observed in $\displaystyle 1$ molal solution./ The depression in freezing point when one mole of non.volatile solute is dissolved in $\displaystyle 1$ kg or 1000g of the solvent.

\[\mathrm{K}_{\mathrm{f}}=\frac{\mathrm{R} \times \mathrm{M}_{\text {solvent }} \times \mathrm{T}_{\mathrm{f}}^{0}}{1000 \times \Delta_{\mathrm{fus}} \mathrm{H}^{0}} \]