Solids and Gases in Liquids

· Describe the effect of solutes on vapour pressure of solvent.

· Describe the effect of solutes on boiling point of the solvent.

· Describe the effect of solutes on freezing point of solvent.

The solubility of gases in water decreases with increased temperature.

As kinetic energy of the dissolved gas particles increases, particles overcome attraction forces.

Increasing pressure increases the solubility of a gas in a liquid.

Forces gas particles into contact with the liquid - increasing the force of attraction - dissolves.

Colligative Properties:

Physical properties of solutions that are affected by the number (not identity) of solute particles dissolved.

Vapour Pressure/ Boiling point / Freezing point

At equilibrium the pressure created by the vapour is called vapour pressure.

In a closed container, a liquid will reach equilibrium between evaporation and condensation.

The solute prevents some solvent particles from reaching surface.

Particles only evaporate from the surface - fewer solvent particles are able to evaporate.

The solute prevents some solvent particles from receiving the energy required to boil.

This increases the temperature at which the solvent boils (boiling point elevation).

The presence of solute interferes with the solvent particles forming a crystal during freezing.

CaCl2 - used in Canada, dissolves exothermically (melts even more ice) and forms 3 ions.

Solvent particles must slow down more to link together to form a crystal - colder temperature.

(freezing point depression)

Na

Cl

· Increase temperature decreases gas solubility

· Increase pressure increases gas solubility,

· Vapour pressure of solvent decreases with solute added.

· Boiling point of the solvent increases with solute added.

· Freezing point of solvent decreases with solute added.