Question

The reagent(s) used for softening the temporary hardness of water is(are)

• A. $Ca_3(PO_4)_2$
• B. $Ca(OH)_2$
• C. $Na_2CO_3$
• D. $NaOCl$

Answer 1

Answer: (D)

$NaOCl$

Answer 2

$Ca(OH)_2 + Ca(HCO_3)_2 \rightarrow 2CaCO_3 \downarrow + _{Clark's\, \, method}^{2H_2O}$
$NaOCl + H_2 \rightarrow NaOH + HOCl$
$HO^- + HCO_3^- \rightarrow CO_3^{2-} + H_2O$
$Ca(HCO_3)_2 + Na_2CO_3 \rightarrow CaCO_3 \downarrow + 2NaHCO_3$