what is Solubility

The maximum amount of a particular solute in grams, which can dissolve in 100 grams of solvent at a given temperature is called solubility.

Solubility =

e.g.Solubility of copper sulphate in water at 20°C is 20.7g and solubility of potassium chloride in water at 20°C is 34g.

A given solution may or not contain the maximum amount of solute in it. The further dissolving capacity of a given solution depends on the amount of solute already present in the solution. On the basis of the capacity of the solution to dissolve certain amount of solute further, the solutions are classified into three types.

SATURATED SOLUTION:

A solution which contains the maximum amount of solute that can be dissolved in the solvent at a given temperature is called saturated solution at that particular temperature. This solution can no longer dissolve any more solute under the given conditions.

UNSATURATED SOLUTION:

The solution containing lesser amount of solute than the saturated solution at a given temperature is called an unsaturated solution. In an unsaturated solution the solvent has the capacity of dissolving more amount of solute at that particular temperature.

SUPERSATURATED SOLUTION:

If a solution holds more solute than the saturated solution at a given temperature, it is called a supersaturated solution.
When more solute is made to dissolve in a saturated solution by raising its temperature and then cooling it slowly without causing any disturbances (like shaking), then the resultant solution holds more solute than the saturated solution.
Supersaturated solution is metastable and slight disturbances like shaking, starting, scratching the wall of the container or adding a solute crystal to the solution make the addition make the additional amount of solute to precipitate out, thereby resulting in the formation of a saturated solution again.