What factors affect freezing point depression?
What factors affect freezing point depression?
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.
Why is freezing point depression ∆ TF is negative?
∆Tf is negative because the temperature of the solution is lower than that of the pure solvent. When determining changes in freezing point (or boiling point), solute concentration is usually not measured in molarity (moles of solute per liter of solution), but, rather, in molality.
What is the purpose of the freezing point depression lab?
PURPOSE/INTRODUCTION The purpose of this experiment is to determine the molecular weight of an unknown substance by measuring the freezing point depression of an aqueous solution of the unknown.
How do you solve 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.
What is the unit of freezing point depression constant?
This is known as Freezing Point Depression Constant or Molal Depression Constant or Cryoscopic Constant. The unit of Kf is K kg mol-1.
Which has higher depression in freezing point?
It can be considered to be a solution of ethanol in water, and its freezing point is lower than water but higher than pure ethanol….Freezing Point Examples.
| Solvent | Normal Freezing Point, oC | Freezing Point Depression, Kb, oC m-1 |
|---|---|---|
| Water | 0.0 | 1.86 |
| Acetic acid | 16.6 | 3.9 |
| Benzene | 5.5 | 5.12 |
| Chloroform | -63.5 | 4.68 |
What is freezing point depression constant?
The freezing point depression is the difference in temperature between the freezing point of the pure solvent and that of the solution. The molal freezing-point depression constant is equal to the change in the freezing point for a 1-molal solution of a nonvolatile molecular solute.