(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 slat. 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.
a. The common salt that we use in your food is obtained by the combination of base - sodium hydroxide (NaOH) and the acid - hydrochloric acid (HCl).
The formula for the common salt that we use in your food is NaCl and its name is sodium chloride.
It is obtained from seawater.
b. When the seas of bygone ages dried-up beds of rock salt were being formed. Rock salts are the deposits of solid salts.
The colour of rock salt is brown. It is brown in colour due to the impurities present in it.
c. When electricity is passed through brine it decomposes to form sodium hydroxide along with the evolution of chlorine gas at anode and hydrogen gas at cathode. Sodium hydroxide solution is also formed near the cathode.
The chemical equation for the above decomposition is: -
2NaCl (aq) +2H2O (l) 
2NaOH (aq) + Cl2 (g) + H2 (g)