Final answer:
The formula ΔTf = Kfm represents the freezing point depression, where ΔTf is the change in freezing point, Kf is the solvent-specific constant, and m is the molality of the solute. To determine the depression, calculate the temperature difference between the pure solvent's freezing point and the solution's freezing point, and then solve for molality using Kf.
Step-by-step explanation:
The formula that shows the decrease in temperature caused by freezing point depression is ΔTf = Kfm, where ΔTf represents the change in freezing point, Kf is the freezing point depression constant for the solvent, and m is the molal concentration of the solute. This phenomenon occurs when a solute is added to a solvent, lowering the vapor pressure and thus the temperature at which the solution freezes. The freezing point depression is directly proportional to the molal concentration of the solute present in the solution.
The strategy to determine the freezing point depression involves two steps. First, use the measured freezing point of the solution and the known freezing point of the pure solvent to calculate ΔTf. Then, with the value of Kf (from tables or literature), solve for the molality of the solution.
Freezing point depression is an important colligative property that can also be compared with boiling point elevation as both are related to the molality of the solution, displaying the effect of solute particles on the freezing and boiling points of a solvent.