What is molal depression constant? Derive an equation.

(N/A) The molal depression constant $(K_f)$,also known as the cryoscopic constant,is defined as the depression in freezing point produced when one mole of a non-volatile solute is dissolved in one kilogram of a solvent.
Let $T_f^0$ be the freezing point of the pure solvent and $T_f$ be the freezing point of the solution. The depression in freezing point is given by $\Delta T_f = T_f^0 - T_f$.
For dilute solutions,the depression in freezing point is directly proportional to the molality $(m)$ of the solution:
$\Delta T_f \propto m$
$\Delta T_f = K_f \cdot m$ --- $(i)$
If $w_2$ grams of a solute with molar mass $M_2$ are dissolved in $w_1$ grams of solvent,the molality $(m)$ is:
$m = \frac{w_2 \times 1000}{M_2 \times w_1}$
Substituting this into equation $(i)$:
$\Delta T_f = K_f \times \frac{w_2 \times 1000}{M_2 \times w_1}$
Rearranging to solve for $M_2$:
$M_2 = \frac{K_f \times w_2 \times 1000}{\Delta T_f \times w_1}$