Question

Temporary hardness of water can be removed by using calcium hydroxide. How ?

Answer 1

`Ca^(2+)+HCO^(-) -> H^+ +CaCO_3` where `Ca^(2+)` is removed as precipitate

Explanation:

Hardness is used to describe water containing large amounts of calcium ions or magnesium ions. In some cases it can also contain `Cl^-, SO_4^(2-), CO_3^(2-),HCO_3^-`

Since it contains these ions, it is difficult to lather and form scum, requiring treatment before the water can be used for things like drinking.

Now there are also 2 types of hardness - temporary and permanent

Temporary hardness refers to when there is dissolved `CO_2` which can be removed by boiling

`Ca^(2+)+HCO^(-) -> H^+ +CaCO_3` where `Ca^(2+)` is removed as precipitate