Question

Temporary hardness may be removed from water by adding :

• A. Ca(OH)2
• B. CaCO3
• C. CaSO4
• D. HCl

Answer 1

Answer: (A)

Ca(OH)2

Answer 2

Ca(OH)2 reacts with Ca(HCO3)2 to precipitate CaCO3

Ca(HCO3)2 + Ca(OH)2  $\longrightarrow$ 2CaCO3 $\downarrow$ + 2H2O

Mg(HCO3)2 + 2Ca(OH)2 $\longrightarrow$2CaCO3 $\downarrow$ Mg (OH)2 $\downarrow$+ 2H2O