A solution of 0.816g of a compound ‘A’ dissolved in 7.5g of Benzene freezes at $1{.59}^0\mathrm{C}$ . The molecular weight of compound ‘A’ if ${\mathrm{K}}_{\mathrm{f}}$ of benzene is 4.9 and melting point of Benzene is $5{.51}^0\mathrm{C}$

It is a colligative property of solutions that is generally proportional to the molality of the added solute. The depression in the freezing point of a solution can be described by the following formula.

ΔT_f =  K_f × m

Where

• ΔT_f is the freezing point depression
• K_f is the cryoscopic constant, and
• m is the molality.