Question

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

• A. ion exchange resins
• B. $Ca(OH{)}_2$
• C. $N{a}_6{P}_6{O}_{18}$
• D. None of the above

Answer 1

The correct option is B $Ca(OH{)}_2$

Temporary hardness due to bicarbonates of calcium and magnesium. Temporary hardness can be removed by Clark's proces, which involves the addition of slaked lime, $Ca(OH{)}_2$.
$Ca\left(HC{O}_3\right)+Ca(OH{)}_2\to 2CaC{O}_3\downarrow +2H_{2}O$