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Assertion : Permanent hardness of water is removed by treatment with washing soda.
Reason : Washing soda reacts with soluble magnesium and calcium sulphate to form insoluble carbonates.
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Reason : Washing soda reacts with soluble magnesium and calcium sulphate to form insoluble carbonates.
Solution:
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If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
Permanent hardness of water is due to the presence of soluble salts of magnesium and calcium in the form of chlorides and sulphates in water. Washing soda reacts with soluble calcium and magnesium chlorides and sulphonates in hard water to form insoluble carbonates.
$\begin{aligned}
&\mathrm{MCl}_2+\mathrm{Na}_2 \mathrm{CO}_3 \longrightarrow \mathrm{MCO}_3 \downarrow+2 \mathrm{NaCl} \\
&\mathrm{MSO}_4+\mathrm{Na}_2 \mathrm{CO}_3 \longrightarrow \mathrm{MCO}_3 \downarrow+\mathrm{Na}_2 \mathrm{SO}_4 \\
&\text { (where } \mathrm{M}=\mathrm{Mg}, \mathrm{Ca} \text { ) }
\end{aligned}$
$\begin{aligned}
&\mathrm{MCl}_2+\mathrm{Na}_2 \mathrm{CO}_3 \longrightarrow \mathrm{MCO}_3 \downarrow+2 \mathrm{NaCl} \\
&\mathrm{MSO}_4+\mathrm{Na}_2 \mathrm{CO}_3 \longrightarrow \mathrm{MCO}_3 \downarrow+\mathrm{Na}_2 \mathrm{SO}_4 \\
&\text { (where } \mathrm{M}=\mathrm{Mg}, \mathrm{Ca} \text { ) }
\end{aligned}$
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