Freezing point lowering expression can be given as ΔTf=Kf m (molality) Which of these assumptio

step 1 In this question, we have been given the expression of delta tf. So this delta tf is going to be

Freezing point lowering expression can be given as ΔTf=Kf m...

Freezing point lowering expression can be given as $\Delta \mathrm{Tf}=\mathrm{K}_{f} \mathrm{~m}$ (molality) Which of these assumption can be considered for the validity of the above relation? a. The $\Delta \mathrm{H}_{f}$ (latent heat of fusion of solvent) is independent of temperature between the actual and normal freezing point b. $\Delta \mathrm{T}_{f}$ is not equal to $3 \mathrm{~K}_{f}$ for $3 \mathrm{~mol} \mathrm{~L}^{-1}$ solution. c. The solid phase consists of pure solvent when solution is allowed to cool. d. The solution is dilute

Freezing point lowering expression can be given as $\Delta \mathrm{Tf}=\mathrm{K}_{f} \mathrm{~m}$ (molality)
Which of these assumption can be considered for the validity of the above relation?
a. The $\Delta \mathrm{H}_{f}$ (latent heat of fusion of solvent) is independent of temperature between the actual and normal freezing point
b. $\Delta \mathrm{T}_{f}$ is not equal to $3 \mathrm{~K}_{f}$ for $3 \mathrm{~mol} \mathrm{~L}^{-1}$ solution.
c. The solid phase consists of pure solvent when solution is allowed to cool.
d. The solution is dilute

Key Concepts

Freezing Point Depression

A colligative property where the addition of a solute to a solvent decreases the freezing point of the resulting solution. The phenomenon is quantified by the equation ?Tf = Kf * m, which relates the freezing point depression to the concentration of the solute in molality. This relationship fundamentally relies on the fact that the change depends only on the number of solute particles rather than their specific nature.

Dilute Solution Approximation

The derivation of the freezing point depression equation assumes that the solution is sufficiently dilute. In such scenarios, interactions between solute particles and deviations from ideality are negligible, ensuring that molality remains an appropriate measure of concentration. This approximation simplifies the treatment of the solution's behavior and underpins the linear relationship indicated by the equation.

Constant Latent Heat of Fusion Assumption

A key assumption in deriving the freezing point depression relationship is that the latent heat of fusion (?Hf) of the solvent remains essentially constant over the temperature range in question. This constancy allows for the integration of the thermodynamic expressions involved and supports the derivation of a simple linear relation between the depression of the freezing point and the solute concentration.

Pure Solvent in the Solid Phase

Another important assumption is that when the solution is cooled, the solid phase that forms is composed of the pure solvent only, with the solute being completely excluded. This ensures that the thermodynamic parameters used in the derivation, such as chemical potentials, are valid and that the relationship between freezing point depression and solute concentration holds true.

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