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Water — CHEMISTRY STD 9 — Question

ICSE BoardEnglish MediumSTD 9CHEMISTRYWater3 Marks
Question
Explain with equation, what is noticed when permanent hard water is treated with
Slaked time
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Answer

Slaked lime
$\mathrm{Ca}\left(\mathrm{HCO}_3\right)_2+\mathrm{Ca}(\mathrm{OH})_2 \xrightarrow{\text { Boil }} 2 \mathrm{CaCO}_3+2 \mathrm{H}_2 \mathrm{O}$ $\mathrm{Mg}\left(\mathrm{HCO}_3\right)_2{ }^{+} \mathrm{Ca}(\mathrm{OH})_2 \xrightarrow{\text { Boil }} \mathrm{MgCO}_3+\mathrm{CaCO}_3+2 \mathrm{H}_2 \mathrm{O}$
Lime is first thoroughly mixed with water in a tank and then fed into another tank containing hard water. Revolving paddles thoroughly mix the two solutions. Most of the calcium carbonate settles down. If there is any solid left over, it is removed by a filter. This is known as Clarke's process.

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