Give the formula which shows the relation between the freezing point and the fusion enthalpy of a solvent.

Bromoform has a normal freezing point of $7.734^{\circ} C$ and its $K_{f} = 14.4^{\circ} C / m$. $A$ solution of $2.60 \ g$ of an unknown substance in $100 \ g$ of bromoform freezes at $5.43^{\circ} C$. What is the molecular weight of the unknown substance?

$A$ solution of $5 \ g$ nonvolatile solute in $50 \ g$ water decreases its freezing point by $0.2 \ K$. Calculate the molar mass of solute if $K_{f}$ of water is $1.86 \ K \ kg \ mol^{-1}$.

Give the unit of $K_f$.

The freezing point depression of a solution containing $0.6 \ g$ of urea (molar mass $= 60 \ g \ mol^{-1}$) in $100 \ mL$ of benzene (in $K$) is ($K_f$ of benzene $= 4.0 \ K \ kg \ mol^{-1}$).

Calculate the cryoscopic constant $(K_f)$ of a solvent if the depression in freezing point of a $0.4 \ m$ solution of a non-volatile solute is $1.8 \ K$.