Question

Equation for the removal of temporary hard water containing Mg(HCO3)2 by addition of slake lime

Answer 1

$\underline{\boxed{\bf{\pink{Hardness\:of\:water:}}}}$

☞ Hardness of water is of two types :

• Temporary hardness : This is due to presence of hydrogen carbonates of magnesium and calcium.
• Permanent hardness : This is due to presence of chlorides and sulphates of magnesium and calcium.

☞ Tamporary hardness can be removed by Boiling or by Clark's method in which lime is added to hard water which precipitates out calcium carbonate and magnesium hydroxide.

✴ Chemical Reaction :

$\underline{\boxed{\bf{\purple{Mg(HCO_3)_2+2Ca(OH)_2\longrightarrow Mg(OH)_2+2CaCO_3}}}}$

☞ Permanent hardness can be removed by :

1. Treatment with washing soda
2. Calgon
3. Ion-exchange or zeolite/permuit process
4. Synthetic resins method