$(a)$ Identify the acid and the base whose combination forms the common salt that you use in your food. Write its formula and chemical name of this salt. Name the source from where it is obtained.
$(b)$ What is rock salt? Mention its colour and the reason due to which it has this colour.
$(c)$ What happens when electricity is passed through brine? Write the chemical equation for it.

(N/A) The common salt used in food is sodium chloride $(NaCl)$. It is formed by the combination of hydrochloric acid $(HCl)$ and sodium hydroxide $(NaOH)$. The primary source of common salt is seawater (ocean water).
$(b)$ Rock salt refers to large deposits of solid salt found in several parts of the world. It is often brown in colour due to the presence of impurities.
$(c)$ When electricity is passed through an aqueous solution of sodium chloride (brine),it decomposes to form sodium hydroxide,chlorine gas,and hydrogen gas. This process is known as the chlor-alkali process. The chemical equation is: $2NaCl(aq) + 2H_2O(l) \xrightarrow{\text{Electricity}} 2NaOH(aq) + Cl_2(g) + H_2(g)$.