The Properties of Mixtures: Solubility

Lecture 18

Saturated solution

contains the maximum amount of dissolved solute at a given

temperature in the presence of undissolved solute.

A saturated solution

In a saturated solution,

processes of dissolving and recrystallizing are in

equilibrium:Solute (undissolved)

Solute (dissolved)

Equilibrium in a saturated solution

Supersaturated solution

contains more than the equilibrium amount of dissolved

solute.It is unstable.

Most solids are more soluble

at higher temperatures.Solute + solvent + heat

saturated solution

Solid solubility vs temperature

Solid solubility vs temperature

Gases are more soluble

at lower temperatures.Solute(g) + water(l)

saturated solution(aq) + heat

Gas solubility vs temperature

Why thermal pollution is bad:Because of increased metabolic rate, living organisms needs more oxygen.Because of lower solubility at the higher temperature, the concentration of oxygen is lower.Because of lower density at the higher temperature, warmer water floats on the cooler and prevent oxygen from reaching it.

Gases are more soluble

at higher pressures.Gas + solvent

saturated solution

The effect of pressure on gas solubility

Henry’s law:

the solubility of a gas (Sgas) is directly proportional to the partial pressure of the gas (Pgas) above the solution:

Sgas = kH x Pgas

kH - Henry’s constant

THE END