Question

How many types of solutions are formed? Write briefly about each type with an example.

Answer 1

Depending upon the physical state of the solute and solvent, solutions may be classified into the following types:

Type of Solution	Solute	Solvent	Common Examples
Gaseous Solutions	Gas	Gas	mixture of oxygen and nitrogen gases
	Liquid	Gas	Chloroform mixed with nitrogen gas
	Solid	Gas	Camphor in nitrogen gas
Liquid Solutions	Gas	Liquid	Oxygen dissolved in water
	Liquid	Liquid	Ethanol dissolved in water
	Solid	Liquid	Glucose dissolved in water
Solid Solutions	Gas	Solid	Solution of hydrogen in palladium
	Liquid	Solid	Amalgam of mercury with sodium
	Solid	Solid	Copper dissolved in gold

1. Gaseous solution: A gaseous solution is a solution in which the solvent is a gas. In these solutions, the solute may be liquid, solid, or gaseous. For example, a mixture of oxygen and nitrogen gas is a gaseous solution.
2. Liquid solution: These solutions are formed by mixing solids or gases in liquids or by mixing two liquids. Some solid substances also form liquid solutions when mixed. For instance, mixing equimolar amounts of sodium and potassium metals at room temperature results in a liquid solution. Oxygen dissolved in water in sufficient quantity protects aquatic organisms in ponds, rivers and seas.
   1. When both the components are completely miscible: In this case, both the liquids are of a similar nature, i.e., either both are polar (e.g., ethyl alcohol and water) or nonpolar (e.g., benzene and hexane).
   2. When both the components are almost miscible: Here, one liquid is polar, and the other is nonpolar in nature, e.g. benzene and water, oil and water, etc.
   3. When both the components are partially miscible: If the intermolecular attraction A-A in liquid A is different from the intermolecular attraction B-B in liquid B, but the A-B attraction is of intermediate order, then both the liquids are limitedly miscible with each other. For example, ether and water are partially mixed.
3. Solid solution: A solid solution is a solution in which the solvent is a solid. The solute may be a gas, a liquid or a solid. For example, gold and copper form solid solutions because gold atoms replace copper atoms in copper crystals, and similarly, copper atoms can replace gold atoms in gold crystals. Alloys of two or more metals are solid solutions.
   Solid solutions can be divided into two classes:
   
   1. Substitutable solid solutions: In these solutions, atoms, molecules or ions of one substance replace the particles of the other substance in the crystal lattice. Brass, copper, and zinc are common examples of solid solutions that are mutually substitutable.
   2. Interstitial solid solutions: In these solutions, atoms of one type occupy the vacancies or gaps present in the lattice of atoms of the other substance. A common example of an interstitial solid solution is tungsten carbide (WC).