Which aqueous solution has the minimum freezing point?

Calculate $\Delta T_{f}$ of aqueous $0.01 \ m$ formic acid if the van't Hoff factor is $1.1$. $[K_{f} = 1.86 \ K \ kg \ mol^{-1}]$ (in $K$)

$0.440 \ g$ of a substance dissolved in $22.2 \ g$ of benzene lowered the freezing point of benzene by $0.567 \ ^oC$. Calculate the molecular mass of the substance. (Given: $K_f = 5.12 \ ^oC \ kg \ mol^{-1}$)

$0.05 \ mol$ of a non-volatile solute is dissolved in $500 \ g$ of water. What is the depression in freezing point of the resultant solution (in $K$)? $(K_f(H_2O) = 1.86 \ K \ kg \ mol^{-1})$

The amount of urea to be dissolved in $500 \ mL$ of water $(K_f = 18.6 \ K \ kg \ mol^{-1})$ to produce a depression of $0.186 \ ^oC$ in freezing point is $....... \ g$. (Assume density of water = $1 \ g/mL$)

Given that $\Delta T_f$ is the depression in freezing point of the solvent in a solution of a non-volatile solute of molality $m$,the quantity $\lim_{m \to 0} \left( \frac{\Delta T_f}{m} \right)$ is equal to: