Solution - A solution is a homogeneous mixture of two or more pure substances which are chemically non-reacting, whose composition can be varied within certain limits. The component which is present in a large proportion in the solution is called solvent and the component present in relatively small proportion is called solute.
Types of solutions : Depending upon the physical state of solvent, solutions can be divided into three main groups :
(a) Gaseous solutions :
(i) Solvent - gas, solute - gas. e.g., air (oxygen and nitrogen).
(ii) Solvent - gas, solute - liquid. e.g., humidity in air.
(iii) Solvent - gas, solute - solid. e.g., camphor in nitrogen.
(b) Liquid solutions :
(i) Solvent - liquid, solute - gas. e.g., aerated drinks.
(ii) Solvent - liquid, solute - liquid. e.g., ethanol in water.
(iii) Solvent - liquid, solute - solid. e.g., salt solution in water.
(c) Solid solutions :
(i) Solvent - solid, solute - gas. e.g., H2 in palladium.
(ii) Solvent - solid, solute - liquid. e.g., amalgam of Hg with Na.
(iii) Solvent - solid, solute - solid. e.g., alloys.