Acids, Bases and Salts

Acids

Curd, lemon juice, orange juice and vinegar taste sour (खट्टा). These substances taste sour because they contain acids.

Acids Occurring in Nature

Name of Acid	Found In
Acetic acid	Vinegar
Formic acid	Ant’s sting
Citric acid	Citrus fruits
Lactic acid	Curd
Oxalic acid	Spinach
Ascorbic acid	Amla, Citrus fruits
Tartaric acid	Tamarind, grapes, unripe mangoes

Bases

Substances which are bitter (कड़वा) in taste and feel soapy (साबुन) on touching are known as bases.

Name of Base	Found In
Calcium hydroxide	Lime water
Ammonium hydroxide	Window cleaner
Sodium hydroxide	Soap
Potassium hydroxide	Soap
Magnesium hydroxide	Milk of magnesia

Indicators

Special type of substances are used to test whether a substance is acidic or basic. These substances are known as indicators indicators. The indicators change their color when added to a solution containing an acidic or a basic substance. Turmeric, litmus, china rose petals, etc., are some of the naturally occurring indicators.

Litmus

The most commonly used natural indicator is litmus. It is extracted from lichens. It has a mauve (purple) color in distilled water. When added to an acidic solution, it turns red and when added to a basic solution, it turns blue.

The solutions which do not change the color of either red or blue litmus are known as neutral solutions. These substances are neither acidic nor basic.

Neutralization

The reaction between an acid and a base is known as neutralization. Salt and water are produced in this process with the evolution of heat.

Example:

Hydrochloric acid (HCl) + Sodium hydroxide (NaOH) → Sodium chloride (NaCl) + Water (H₂O)