Substances are classified into acids, bases and salts depending on their chemical behavior and properties. Acids are of sour taste and turn blue litmus to red. Bases are soapy to touch and turn red litmus to blue. According to Lewis, electron pair accept or is an acid and electron pair donor is a base. The strength of acid or base depends on the concentration of H3O +ions or OH– produced in the solution. If an acid consists more H3O +ions, then it is a strong acid, if the H3O+ ions are fewer then it is a weak acid. A scale for measuring hydrogen ion concentration in a solution is called ‘pH’ scale.
The pH scale ranges from 0 to 14. Acid pH value varies from 0 to 7. Neutral substances have pH value 7. pH value is 7 to 14 for Base. When acid reacts with base, it forms salt and water. Sodium chloride is the most common salt. Sodium hydroxide, Bleaching powder, baking soda, washing soda are some of the salts obtained from common salt. Plaster of Paris is obtained from gypsum.