Question

Permanent hardness is due to the presence of soluble salts of Mg and Ca in the form of chlorides and sulphates in${{H}_{2}}O$. It can be removed by:A. BoilingB. The Clark’s methodC. Treatment with $N{{a}_{2}}C{{O}_{3}}$D. All of these.

The permanent hardness of water is due to the presence of soluble salts of magnesium and calcium in the form of chlorides and sulphides in the water. We cannot remove this permanent hardness by simple boiling. We can treat this permanent hard water with washing soda ($N{{a}_{2}}C{{O}_{3}}$) to remove this hardness. When washing soda ($N{{a}_{2}}C{{O}_{3}}$) is reacts with the sulphide and chloride salts of magnesium and calcium, insoluble carbonates are formed. Thus, we can convert this hard water to soft water.
So, treatment with washing soda ($N{{a}_{2}}C{{O}_{3}}$) is a method to remove the permanent hardness of water. Therefore, the correct option is ‘C. treatment with $N{{a}_{2}}C{{O}_{3}}$’.