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The reagent(s) used for softening the temporary hardness of water is(are)
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1720 Upvotes
Verified Answer
The correct answers are:
$\mathrm{Ca}(\mathrm{OH})_2$
,
$\mathrm{Na}_2 \mathrm{CO}_3$
,
$\mathrm{NaOCl}$
$\mathrm{Ca}(\mathrm{OH})_2$
,
$\mathrm{Na}_2 \mathrm{CO}_3$
,
$\mathrm{NaOCl}$
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
$$
\begin{gathered}
\mathrm{Ca}\left(\mathrm{HCO}_3\right)_2+\mathrm{Ca}(\mathrm{OH})_2 \longrightarrow \\
2 \mathrm{CaCO}_3 \downarrow+2 \mathrm{H}_2 \mathrm{O} \\
\mathrm{Ca}\left(\mathrm{HCO}_3\right)_2+\mathrm{Na}_2 \mathrm{CO}_3 \longrightarrow \\
\mathrm{CaCO}_3 \downarrow+2 \mathrm{NaHCO}_3
\end{gathered}
$$
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
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