Freezing point depression in terms of intermolecular forces

This leads to a lower freezing point compared to the pure solvent.In summary, freezing point depression is a phenomenon that occurs when the IMFs between the solvent and solute are strong enough to disrupt the freezing process, causing a lower freezing point compared to the pure solvent. This is due to the solvent more readily associating with the solute molecules instead of forming its solid structure.
  • #1
BrianC12
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Sorry if this is an obvious question...I understand how the justification via the pressure v temp graph works, but I'm not quite understanding freezing point depression in terms of intermolecular forces and temperature. I was taught that due to attractive IMF between solute and solvent particles in solution, vapor pressure will be lowered, and therefore higher temperature is needed to boil. But if that's the case, then doesn't that mean the same attractive IMF will overcome the kinetic energy of the molecules at a higher temperature than pure solvent, resulting in an increase of freezing point?

Thanks for any help!
 
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  • #2
Freezing point depression relies on the fact that the IMFs between the solvent and solute are strong enough to disrupt the freezing process. The solvent more readily associates with the solute molecules instead of forming its solid structure.
 

1. What is freezing point depression?

Freezing point depression is a phenomenon where the freezing point of a solvent is lowered when a solute is added to it. This occurs due to the disruption of intermolecular forces between solvent molecules.

2. How does intermolecular forces affect freezing point depression?

Intermolecular forces, such as hydrogen bonding and London dispersion forces, hold molecules together in a liquid state. When a solute is added to a solvent, it interferes with these forces, making it more difficult for the solvent molecules to arrange into a solid structure, thus lowering the freezing point.

3. What factors influence the extent of freezing point depression?

The amount of solute added, as well as the type of solute and solvent, can affect the extent of freezing point depression. Additionally, the strength of the intermolecular forces in the solvent and solute molecules also play a role.

4. Can freezing point depression be used to determine the molecular weight of a solute?

Yes, the degree of freezing point depression is directly proportional to the amount of solute present in the solution. By measuring the freezing point depression and knowing the concentration of the solute, the molecular weight of the solute can be calculated using the formula ΔT = Kf*m*i, where ΔT is the freezing point depression, Kf is the molal freezing point depression constant, m is the molality of the solution, and i is the van't Hoff factor.

5. How is freezing point depression used in real-world applications?

Freezing point depression is a commonly used concept in industries such as food preservation and antifreeze production. By adding solutes to liquids, the freezing point can be lowered, preventing the formation of ice crystals and thus preserving the quality of food products. In antifreeze, the addition of solutes to water reduces its freezing point, allowing it to remain in a liquid state at lower temperatures, preventing damage to engines during winter months.

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