A solution prepared by dissolving 3.00 g of ascorbic acid (vitamin C, C6H8O6) in 50.0 g of acetic acid has a freez- ing point that is depressed by ΔT = 1.33 °C below that ofpure acetic acid. What is the value of the molal freezing- point-depression constant for acetic acid?

Key Concepts

Freezing Point Depression

Freezing point depression is a colligative property that describes the lowering of a solvent's freezing point when a solute is added. The extent of this depression is directly proportional to the number of solute particles in the solution, which can be calculated using the formula ΔT = Kf * m, where ΔT is the change in freezing point, Kf is the molal freezing-point depression constant, and m is the molality of the solution.

Molality

Molality (m) is a measure of concentration defined as the number of moles of solute per kilogram of solvent. It is particularly useful in colligative property calculations because it accounts for the mass of the solvent, allowing for accurate determination of how the addition of solute affects properties like freezing point and boiling point.

Molar Mass of Ascorbic Acid

The molar mass of ascorbic acid (C6H8O6) is essential for converting grams of the solute into moles, which is necessary for calculating molality. The molar mass can be determined by summing the atomic masses of all the atoms in the molecular formula, allowing for the correct application of the freezing point depression formula in the context of the given problem.