The reagent(s) used for softening the temporary hardness of water is(are)
The reagent(s) used for softening the temporary hardness of water is(are)
$\mathrm{Ca}_3\left(\mathrm{PO}_4\right)_2$
$\mathrm{Ca}(\mathrm{OH})_2$
$\mathrm{Na}_2 \mathrm{CO}_3$
$\mathrm{NaOCl}$
Solution
Softening the temporary hardness of water means conversion of bicarbonate into calcium carbonate (precipitation)
$
\begin{gathered}
\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} \\
\mathrm{Ca}\left(\mathrm{HCO}_3\right)_2+\mathrm{Na}_2 \mathrm{CO}_3 \longrightarrow \\
\mathrm{CaCO}_3 \downarrow+2 \mathrm{NaHCO}_3
\end{gathered}
$
Even $\mathrm{NaOCl}$ can be used, as in aqueous medium $\overline{\mathrm{O}} \mathrm{Cl}$ gets hydrolysed and makes solution alkaline enough to cause precipitation of $\mathrm{CaCO}_3$.
$
\begin{aligned}
\mathrm{NaOCl}+\mathrm{H}_2 \mathrm{O} & \rightleftharpoons \mathrm{HOCl}+\mathrm{NaOH} \\
\mathrm{OH}^{-}+\mathrm{HCO}_3^{-} & \longrightarrow \mathrm{CO}_3^{2-}+\mathrm{H}_2 \mathrm{O}
\end{aligned}
$
Representative elements (Hydrogen and its compounds)
Conceptual
II