Question

# In permanent hardness of water, when washing soda is treated with water, _____is precipitated outA.Sodium carbonateB.Magnesium carbonateC.Calcium carbonateD.$N{a_2}C{O_3}$ and $MgC{O_3}$

Hint: Permanent hardness of water is due to presence of soluble chlorides and sulphates of $M{g^{2 + }}$ and $C{a^{2 + }}$. This hardness is removed by washing soda. It is generally difficult to remove the permanent hardness by boiling.

Washing soda is a chemical compound with the formula $N{a_2}C{O_3}$ known as sodium carbonate, and it is a salt of carbonic acid. It is a natural cleaner and a powerful water softener. It is very basic with a pH of $11$
$C{a^{2 + }} + N{a_2}C{O_3} \to CaC{O_3} + 2N{a^ + }$