Question

By adding which of the following process, permanent hardness of water can be removed.
A. Sodalime
B. Sodium bicarbonate
C. Washing soda
D. Sodium chloride

Answer 1

Correct Answer - c
Washing soda removes both the temporary and permanent hardness by converting soluble calcium and magnesium compounds into insoluble carbonates.
`CaCl_(2) Na_(2)CP_(3) rarr CaCO_(3)+2NaCl`
`CaSO_(4) +Na_(2)CO_(3) rarr CaCO_(3) +Na_(2)SO_(4)`
`Ca(HCO_(3))_(2)+Na_(2)CO_(3)rarr CaCO_(3)+2NaHCO_(3).`