Easy MCQ +4 / -1 PYQ · JEE Mains 2022

The metal salts formed during softening of hardwater using Clark's method are :

  1. A $\mathrm{Ca}(\mathrm{OH})_{2}$ and $\mathrm{Mg}(\mathrm{OH})_{2}$
  2. B $\mathrm{CaCO}_{3}$ and $\mathrm{Mg}(\mathrm{OH})_{2}$ Correct answer
  3. C $\mathrm{Ca}(\mathrm{OH})_{2}$ and $\mathrm{MgCO}_{3}$
  4. D $\mathrm{CaCO}_{3}$ and $\mathrm{MgCO}_{3}$

Solution

In Clark's method, calculated amount of lime is added to hard water. It precipitates out calcium carbonate and magnesium hydroxide which can filtered off. <br/><br/> $$ \begin{aligned} &\mathrm{Ca}\left(\mathrm{HCO}_{3}\right)_{2}+\mathrm{Ca}(\mathrm{OH})_{2} \rightarrow 2 \mathrm{CaCO}_{3} \downarrow+2 \mathrm{H}_{2} \mathrm{O} \\\\ &\mathrm{Mg}\left(\mathrm{HCO}_{3}\right)_{2}+2 \mathrm{Ca}(\mathrm{OH})_{2} \rightarrow 2 \mathrm{CaCO}_{3} \downarrow+\mathrm{Mg}(\mathrm{OH})_{2}+2 \mathrm{H}_{2} \mathrm{O} \end{aligned} $$

About this question

Subject: Chemistry · Chapter: p-Block Elements · Topic: Group 13: Boron Family

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