Colligative Properties and Raoult's Law

Colligative Properties

Depend on number of solute particles, not identity.

Vapor Pressure

Pressure exerted by vapor above a liquid.

Raoult's Law

Vapor pressure proportional to solvent's mole fraction.

Mole Fraction

Ratio of moles of component to total moles.

Positive Deviation

Vapor pressure higher than expected from Raoult's Law.

Negative Deviation

Vapor pressure lower than expected from Raoult's Law.

Boiling Point Elevation

Increase in boiling point due to solute presence.

Freezing Point Depression

Decrease in freezing point due to solute presence.

Normal Boiling Point

Temperature where vapor pressure equals atmospheric pressure.

Vapor Pressure Lowering

Reduction in vapor pressure due to solute.

Molality

Moles of solute per kilogram of solvent.

Kb

Molal boiling point elevation constant for solvent.

Kf

Molal freezing point depression constant for solvent.

ΔTb

Change in boiling point due to solute.

ΔTf

Change in freezing point due to solute.

Intermolecular Forces

Attractive forces between molecules affecting properties.

Nonvolatile Solute

Solute that does not vaporize significantly.

Ideal Solution

Solution where solute-solvent interactions are similar.

Non-Ideal Behavior

Deviation from Raoult's Law due to differing interactions.

Osmotic Pressure

Pressure required to stop osmosis in solutions.

Ethanol and Water

Example of positive deviation in vapor pressure.

Trichloromethane and Ethoxyethane

Example of negative deviation in vapor pressure.

Salting Roads

Practical application of freezing point depression.

Ice Cream Making

Uses freezing point depression for texture.