A substance which dissolves in water to give hydrogen ions as the only positively charged ions is called an acid. The acids prepared from the minerals of the earth are known as mineral acids.

Eg. Sulphuric Acid, Nitric Acid, Hydrochloric Acid, Phosphoric Acid.

Acids can be classified as strong and weak.

Strong Acids are acids that dissolve in water to give a large number of positively charged hydrogen ions.

Weak Acids are acids that dissolve in water to give a smaller amount of positively charged hydrogen ions.

Concenrated acids have less or no water.

Diluted acids are solutions of acids.

Natural Source


Oranges and lemons

Citric Acid

Grapes, Tamarind and Goose Berries

Tartaric acid

Tomatoes, Spinach

Oxalic Acid

Sour Milk

Lactic Acid


Acetic Acid


Malic Acid


Amino Acid

Some Common Acids with their formulae


Chemical Name


Hydrochloric acid

Hydrogen Chloride


Sulphuric Acid

Hydrogen Sulphate


Nitric Acid

Hydrogen Nitrate


Phosphoric Acid

Hydrogen Phosphate


Sulphurous Acid

Hydrogen Sulphite


Nitrous Acid

Hydrogen Nitrite


Carbonic Acid

Hydrogen Carbonate


General Physical Properties of Acids :

  1. They have a sour taste.
  2. All acids have hydrogen atoms in them.
  3. They turn blue litmus red.
  4. They turn methyl orange solution pink
  5. They donot affect phenolphthalein solution
  6. Strong acids have a corrosive action on skin. They cause painful blisters.
  7. Most of the acids are soluble in water.
  8. Acid solutions are good conductors of electricity.
Uses of Acid :

Sulphuric acid

  • Manufacture of fertilizers
  • Batteries of cars, buses, trucks and inverter batteries.
  • Manufacture of dyes, drugs, paints, plastics, detergents etc.
Hydrochloric Acid

  • Cleaning metal surfaces during timing and galvanising
  • Used in dyeing industry
  • Used for preparing glucose from starch
  • Used for descaling the steam boilers
  • Used in cleaning kitchen sinks and other sainitary ware.
Nitric Acid

  • It is used for manufacture of fertilizers such as Ammonium Nitrate and Calcium Nitrate
  • It is used in manufactures of TNT and TNG.
  • It is used in purification of metals such as gold and silver by goldsmiths
Phosphoric Acid
  • It is used for manufacturing Phosphatic fertilizer
Carbonic Acid
  • It is commonly called plain soda. Mixed with citric acid and sugar, it is used for making soft drinks.
Acetic acid
  • It is used as a table acid and for the preservation of food articles
Tartaric Acid
  • It is used in the manufacture of baking powder

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