Freezing point depression is the phenomena that describes why adding a solute to a solvent results in the lowering of the freezing point of the solvent. When a substance starts to freeze, the molecules slow down due to the decreases in temperature, and the intermolecular forces start to take over.

Does every solvent have the same freezing-point depression constant?

The proportionality constant, Kf, is called the molal freezing-point depression constant. It is a constant that is equal to the change in the freezing point for a 1-molal solution of a nonvolatile molecular solute. Every solvent has a unique molal freezing-point depression constant.

How do you calculate freezing-point depression?

The freezing point depression ∆T = KF·m where KF is the molal freezing point depression constant and m is the molality of the solute. Rearrangement gives: mol solute = (m) x (kg solvent) where kg of solvent is the mass of the solvent (lauric acid) in the mixture. This gives the moles of the solute.

How do you find the freezing point on a graph?

freezing point of the solution is determined from the graph by drawing two straight lines through the data points above and below the freezing point. The temperature corresponding to the intersection of the two lines is the freezing point of the solution.

What is depression in freezing point Class 12?

According to Raoult’s law, addition of non-volatile solute decreases the vapour pressure of the solvent and would be equal to that of solid solvent at lower This decreases the freezing point of thesolvent. The decrease in the freezing point = ΔTf = Tf – Tf0. This is known as depression in freezing point.

What is the reason for depression in freezing point?

The explanation for the freezing point depression is then simply that as solvent molecules leave the liquid and join the solid, they leave behind a smaller volume of liquid in which the solute particles can roam. The resulting reduced entropy of the solute particles thus is independent of their properties.

What is freezing point depression of water?

Freezing-point depression is what causes sea water, (a mixture of salt and other compounds in water), to remain liquid at temperatures below 0 °C (32 °F), the freezing point of pure water.

How do intermolecular forces affect freezing point depression?

Molecules with stronger intermolecular forces are pulled together tightly to form a solid at higher temperatures, so their freezing point is higher. Molecules with lower intermolecular forces will not solidify until the temperature is lowered further.

Why is the freezing point of a pure solvent constant?

When a pure solvent freezes, its particles become more ordered as the intermolecular forces that operate between the molecules become permanent. As a result, more energy must be removed from the solution in order to freeze it, and the freezing point of the solution is lower than that of the pure solvent.

What is the freezing point depression of a solution?

where Δ T f is the freezing point depression, T f (solution) is the freezing point of the solution, T f (solvent) is the freezing point of the solvent, K f is the freezing point depression constant, and m is the molality.

How does the solute affect the freezing point?

The solute lowers the vapor pressure of the solvent, resulting in a lowering of the freezing point of the solution compared to the solvent. The freezing point depression is the difference in temperature between the freezing point of the pure solvent and that of the solution. On the graph, the freezing point depression is represented by Δ T f.

What is the molal freezing point depression constant (Kf)?

Note that the molal freezing point depression constant, Kf, has a specific value depending on the identity of the solvent. solvent normal freezing point, oC Kb, oC m-1

What is the relationship between molal concentration and freezing point?

Experimentally, we know that the change in freezing point of the solvent in a solution from that of the pure solvent is directly proportional to the molal concentration of the solute: T = Kfm where: Tis the change in freezing point of the solvent,