Colligative Properties

What is the definition of a colligative property?

Properties that depend on the concentration of solute particles, but not on their identity.

In calculations involving colligative properties, concentration is provided by what?

Molality

What is the equation for molality?

M= moles of solute/kg of solvent

What are the 4 colligative properties?

Vapor Point Reduction

Boiling Point Elevation

Freezing Point Depression

Osmotic Pressure

What happens during Vapor pressure reduction?

nonvolatile solute is added to a pure solvent, the solute molecules take up space at the surface preventing solvent molecules from leaving and reentering the liquid.

Few what exist above the liquid causing vapor pressure reduction?

gas molecules

Boiling point is the temperature at which vapor pressure above a liquid equalizes with what?

Atmospheric Pressure

Because solute addition reduces vapor pressure a what temp is necessary to get the vapor pressure up to atmospheric pressure so that it boils?

Higher

The amount by which the boiling point is raised by solute addition is called what?

boiling point elevation

The BPE is the difference between the boiling point of the what and that of the solution

Pure solvent

The BPE is directly proportional to what?

Molality

What is the equation for BPE?

Tb = Kb x m

what is Kb?

molal boiling point constant

The ability of a dissolved solute to lower the freezing point of its solution is known as what?

Freezing Point Depression

The decrease in the freezing point is directly proportional to what?

molality of the solution

What is the equation for FPD?

Tf = Kf x m

What is osmosis?

Net flow of solvent molecules from the less concentrated to the more concentrated

What does it mean to be semipermeable?

allow certain particles to pass through

two solutions with identical osmotic pressure are said to be what?

Isotonic

one solution has a lower osmotic pressure than another it is said to be?

hypotonic

one solution has a higher osmotic pressure than another it is said to be?

hypertonic