could freezing point depression be used for substances not soluble in water?
For determining what? molar mass? No.
Yes, freezing point depression can be used for substances that are not soluble in water. Freezing point depression is a colligative property, which means it depends only on the number of solute particles in a given solution, regardless of the nature of the solute. Therefore, it can be applied to any solvent and solute combination, whether they are soluble in water or not.
To utilize freezing point depression for substances not soluble in water, an appropriate solvent needs to be selected. Different solvents have different freezing points, and the solute can be added to the solvent to lower its freezing point. This allows for the determination of the molecular weight or the amount of the solute present in the solution.
For example, non-polar solvents like benzene or toluene can be used for substances not soluble in water. By measuring the freezing point depression of the solvent after adding the solute, you can calculate the concentration or molecular weight of the solute using colligative property equations.
It's worth noting that the choice of solvent depends on the specific properties of the solute and the desired experimental conditions.
Yes, freezing point depression can be used to determine the molecular weight or molar mass of substances, even if they are not soluble in water. Freezing point depression is a colligative property, meaning it depends on the number of solute particles present in a solvent rather than the nature of the solute.
To determine the molecular weight of a substance using freezing point depression, you would need to follow these steps:
1. Dissolve a known amount of the substance in a suitable solvent. If the substance is not soluble in water, you will need to use an appropriate solvent in which the substance is soluble.
2. Measure the freezing point of the pure solvent. This can be done using a thermometer or a freezing point depression apparatus.
3. Next, measure the freezing point of the solution containing the solute. Again, you can use a thermometer or an apparatus designed for freezing point depression measurements.
4. Calculate the freezing point depression (∆T) by subtracting the freezing point of the solution from the freezing point of the pure solvent (∆T = freezing point of pure solvent - freezing point of the solution).
5. Finally, use the formula for freezing point depression to calculate the molecular weight of the solute:
ΔT = Kf * m * i
where ΔT is the freezing point depression, Kf is the cryoscopic constant of the solvent, m is the molality of the solution (moles of solute divided by kilograms of solvent), and i is the van't Hoff factor, which represents the number of particles the solute dissociates into in the solution.
By rearranging the formula, you can solve for the molecular weight (M) of the solute:
M = ΔT / (Kf * m * i)
It is important to note that the accuracy of the molecular weight determination using freezing point depression depends on the purity of the solute and the accuracy of the measurements made.