sblock Elements 1 Question 17
17. What is reason of temporary hardness of water?
(2019 Main, 9 Jan II)
(a) $\mathrm{Na}_2 \mathrm{SO}_4$
(b) $\mathrm{CaCl}_2$
(c) NaCl
(d) $\mathrm{Ca}\left(\mathrm{HCO}_3\right)_2$
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Answer:
Correct Answer: 17. (d)
Solution: Temporary hardness of water is due to presence of soluble $\mathrm{Ca}\left(\mathrm{HCO}_3\right)_2$ or $\mathrm{Mg}\left(\mathrm{HCO}_3\right)_2$.
Permanent hardness of water is due to the presence of $\mathrm{CaCl}_2$ or $\mathrm{CaSO}_4$ or $\mathrm{MgCl}_2$ or $\mathrm{MgSO}_4$.
Temporary hardness of water is also called carbonate hardness which can be easily removed by boiling or by treatment with $\mathrm{Ca}(\mathrm{OH})_2$ (Clark’s method).
BETA
