Acids can be categorised in different ways based on the following factors:
  1. Source
  2. Basicity
  3. Ionisation
  4. Concentration
Based on the source of origin, the acid is classified as
  1. Organic acid
  2. Inorganic or mineral acid
Organic acid:
Acids obtained from plants and animals (living things) are known as organic acids, which also called carboxy acids. These are generally known as weak acids.
Example: Acetic acid, formic acid, citric acid, lactic acid, malic acid, tannic acid.
Inorganic acid:
Acids prepared from rocks and minerals are inorganic acids or mineral acids.
Example: Nitric acid, hydrochloric acid, sulphuric acid.
The number of replaceable hydrogen atoms found in one molecule of acid is referred to as basicity.
For example, acetic acid (\(CH_3COOH\)) has four hydrogen atoms, but only one of them can be replaced. Hence, it is monobasic.
Based on their basicity, inorganic acids are classified into monobasic, dibasic and tribasic acid.
Monobasic acid: Monobasic acid is an acid that has only one replaceable hydrogen atom per molecule. This is because it produces one hydrogen ion per molecule of acid in the solution. Example: \(HCl\), \(HNO_3\)
Dibasic acid: In solution, an acid produces two hydrogen ions per molecule of the acid. Example: \(H_2SO_4\), \(H_2CO_3\) (carbonic acid)
Tribasic acid: In solution, an acid produces three hydrogen ions per molecule of the acid. Example: \(H_3PO_4\) (phosphorous acid)
The process of being dissociated into ions by heat, radiation, chemical reactions or electrical discharge is known as ionisation. Strong acids are those that are completely ionised in water, while weak acids are only partially ionised.
Example: \(HCl\) is a strong acid, while \(CH_3COOH\) is a weak acid.
Note: Acids do not ionise in an organic solvent such as ethanol, methanol, butanol, glucose, etc.
Concentrated acid is a relatively large amount of acid dissolved in a solvent, while dilute acid is a smaller amount of acid dissolved in a solvent.
When mixing any concentrated inorganic acid with water, extreme caution is needed. Since the acid produces a lot of heat, it must be added slowly and carefully to the water with constant stirring. If acid is mixed with water, the mixture splashes out of the bottle, and it may cause burns.