“Solubility of a substance may be defined as the amount of solute dissolved in 100gms of a solvent to form a saturated solution at a given temperature”. A saturated solution is a solution which contains at a given temperature as much solute as it can hold in presence of dissolveding solvent. Any solution may contain less solute than would be necessary to saturate it. Such a solution is known as unsaturated solution. When the solution contains more solute than would be necessary to saturate it then it is termed as supersaturated solution.
Kinds of solutions
All the three states of matter (gas, liquid or solid) may behave either as solvent or solute. Depending on the state of solute or solvent, mainly there may be following nine types of binary solutions.
|Gas||Gas||Mixture of gases, air.|
|Gas||Liquid||Water vapours in air, mist.|
|Gas||Solid||Sublimation of a solid into a gas, smoke.|
|Liquid||Gas||CO2 gas dissolved in water (aerated drinks).|
|Liquid||Liquid||Mixture of miscible liquids, e.g., alcohol in water.|
|Liquid||Solid||Salt in water, sugar in water.|
|Solid||Gas||Adsorption of gases over metals; hydrogen over palladium.|
|Solid||Liquid||Mercury in zinc, mercury in gold, CuSO4.5H2O.|
|Solid||Solid||Homogeneous mixture of two or more metals (alloys), e.g., copper in gold, zinc in copper.|
Among these solutions the most significant type of solutions are those which are in liquid phase and may be categorised as,
(1) Solid in liquid solutions,
(2) Liquid in liquid solutions and
(3) Gas in liquid solutions.