Final answer:
The melting point depression equation is applicable to dilute solutions with nonvolatile solutes, where the freezing point is decreased in proportion to the solute's molality.
Step-by-step explanation:
The melting point depression equation is only valid for dilute solutions of nonvolatile solutes. This phenomenon, known as freezing point depression, occurs when the addition of a solute lowers the freezing point of the solution compared to the pure solvent.
The relation between freezing point depression and solute molality is given by the equation ΔTf = Kf * m, where ΔTf is the freezing point depression, Kf is the molal freezing-point depression constant, and m is the molality of the solution. Each solvent has a characteristic value for Kf. The depression in freezing point is also affected by the number of particles the solute provides in solution, for example, NaCl would have twice the effect of glucose at the same molality, because NaCl dissociates into two particles in solution.