Temporary hardness of water is removed in Clark's process by adding
Temporary hardness of water is removed in Clark's process by adding
caustic soda
calgon
borax
lime
Solution
The temporary hardness of water is due to the presence of bicarbonates of $\mathrm{Ca}$ and $\mathrm{Mg}$. This may be removed by Clark's process. In this process, addition of calculated quantity of lime causes precipitation of $\mathrm{CaCO}_3$ as
$
\begin{array}{r}
\mathrm{Ca}\left(\mathrm{HCO}_3\right)_2+\mathrm{Ca}(\mathrm{OH})_2 \longrightarrow 2 \mathrm{CaCO}_3 \downarrow+2 \mathrm{H}_2 \mathrm{O} \\
\text { and } \mathrm{Mg}\left(\mathrm{HCO}_3\right)_2+2 \mathrm{Ca}(\mathrm{OH})_2 \underset{2}{\longrightarrow} 2 \mathrm{CaCO}_3 \downarrow \\
+\mathrm{Mg}(\mathrm{OH})_2+2 \mathrm{H}_2 \mathrm{O}
\end{array}
$