(a) What is the importance of pH in everyday life ?
(b) How are sodium hydroxide and `Cl_(2)` (Chlorine) gas produced from common salt. What is this process called?

Explanation

(a) (i) Living organisms can survive only in a narrow range of pH change. Acidic rain water when flows into the rivers, it lowersthe pH value of river water and makes the survival of acquatic life in such river water difficult. Plants require a specific pH range for their healthy growth.
(ii) Our stomach and intestines work in a specific pH range. Stomach acts in slightly acidic medium while small intestine digests the food in slightly alkaline medium.
(iii) Tooth decay starts when the pH of the mouth is lower than 5.5.
(b) When electircity is passed through an aqueous solution of sodium chloride (called brine), it decomposes to form sodium hydroxide. This process is called Chlor-alkali process because the products formed are chlorine and alkali NaOH.
`2NaCl (aq)+2H_(2)O(I) to 2NaOH(aq)+Cl_(2)(g)+H_(2)(g)`
`Cl_(2)` gas is given off at the anode and `H_(2)` gas at the cathode while sodium hydroxide solution is formed near the cathode.