acids

CBSE Class X >> Science>> Acids
Acids
The word “acid” comes from the Latin word “acidus,” which means sour. Any substance that releases hydrogen ions when dissolved in water is an acid.

The word “acid” comes from the Latin word “acidus,” which means sour. Any substance that releases hydrogen ions when dissolved in water is an acid.

Acids obtained from food like curd, lemons, grapes, raw mango, citrus fruits and gooseberry are called organic acids. Hydrochloric acid, sulphuric acid and nitric acid are called inorganic or mineral acids.

Acids turn blue litmus red, methyl orange red and have corrosive action on skin, and are good conductors of electricity. The action of acids with water is exothermic as heat is generated on dilution.

Acids react with metals to form metal salts. In this reaction, hydrogen gas is liberated. Acids react with metal carbonates to form corresponding salts, carbon dioxide and water. Acids react with metal hydrogen carbonates and form corresponding salts, carbon dioxide and water. Acids react with metal oxide to form salt and water.

An acid base indicator is the one which exhibits different colour in acids and bases. Red cabbage is a visual indicator used to detect acids.

Onions are called olfactory indicators. Litmus is a natural indicator and is extracted from lichens.
Apart from natural indicators there are a few synthetic indicators, such as methyl orange and phenolphthalein.

•Methyl orange turns red in an acid and yellow in a base.
•Phenolphthalein does not change colour in an acid. It turns pink in a base.
•Sulphuric acid is used in the manufacture of fertilisers, paints, dyes, chemicals, plastics and synthetic fibres. It is also used in car batteries.
•Nitric acid is used in the manufacture of fertilisers, explosives like TNT, dyes and drugs.
•Hydrochloric acid is used before galvanising, to remove oxide film from steel and also as a descaling agent for boilers. It is also used in the textile, leather and food industry.