10th Class Science Acids, Bases and Salts / अम्ल, क्षार एवं लवण Acid, Bases and Salts

 Acids, Bases and Salts

• Acids

The term acid has its origin in the latin word acidus, meaning sour.

• An acid is a substance that has a sour taste. It is defined as a compound which contains replaceable hydrogen in it.

• Acids that contain both hydrogen and oxygen are called oxyacids.

• Acids that contain hydrogen and other non-metallic elements except oxygen are called hydracids.

• Properties of Acids

Acids have a sour taste, turn blue litmus to red, conduct electricity and react with metals to form salt and hydrogen gas.

• Bases

A base is a substance, usually the oxide or the hydroxide of a metal, which can react with an acid to produce salt and water.

• Alkalis are bases that are soluble in water.

• The strength of a base is determined by the amount of hydroxide ions that the base provides when dissolved in water.

• Properties of Bases

Bases have bitter taste, soapy to touch, turn red litmus to blue and react with metals to form hydrogen gas.

• pH Scale

In 1909 Sorensen devised a scale (known as pH scale) on which the strength of acid solutions as well as basic solutions could be represented by making use of the hydrogen ion concentrations in them.

• The pH of a solution is inversely proportional to the concentration of hydrogen ions in it. In the term pH, letter 'p' stands for a German word 'potenz' which means 'power' and letter H stands for hydrogen ion concentration\[[{{H}^{+}}]\]

(i) Acids (or acidic solutions) have a pH of less

than 7.

(ii) Bases (or basic solutions) have a pH of more

than 7.

(iii) Neutral substances have a pH of exactly 7.