Question

Which of the following process permanent hardness of water can be removed, by adding.

• A. Sodalime
• B. Sodiumbicarbonate
• C. Washing soda
• D. Sodium chloride

Answer 1

Answer: (C)

Washing soda

Answer 2

Washing soda removes both the temporary and permanent hardness by converting soluble calcium and magnesium compounds into insoluble carbonates.

$CaCl_{2} + Na_{2}CO_{3} \rightarrow CaCO_{3} + 2NaCl$

$CaSO_{4} + Na_{2}CO_{3} \rightarrow CaCO_{3} + Na_{2}SO_{4}$

$Ca(HCO_{3})_{2} + Na_{2}CO_{3} \rightarrow CaCO_{3} + 2NaHCO_{3}.$