Question

Permanent hardness of water can be removed by adding

• A. $Na_{2}CO_{3}$
• B. $K$
• C. $Ca(OCl)Cl$
• D. $Cl_{2}$

Answer 1

Answer: (A)

$Na_{2}CO_{3}$

Answer 2

Washing soda, $\left( Na _{2} CO _{3} \cdot 10 H _{2} O \right)$ is used to remove permanent hardness of water. It converts $Ca ^{2+}$ and $Mg ^{2+}$ salts (soluble) to carbonates (insoluble). $Ca \left( HCO _{3}\right)_{2}+ Na _{2} CO _{3} \rightarrow CaCO _{3} \downarrow+2 NaHCO _{3}$ $MgCl _{2}+ Na _{2} CO _{3} \rightarrow MgCO _{3} \downarrow+2 NaCl$