Question

Which one of the following processes will not produce hard water?

• A. Saturation of water with $MgC{l}_2$
• B. Saturation of water with $CaS{O}_4$
• C. Saturation of water with $N{a}_{2}S{O}_4$
• D. Saturation of water with $MgS{O}_4$

Answer 1

The correct option is C Saturation of water with $N{a}_{2}S{O}_4$

Hardness of water is of two type. Permanent hardness and temporary hardness. Permanent hardness is due to chlorides and sulphates of calcium and magnesium i.e. $CaC{l}_2,CaS{O}_4,MgC{l}_2$ and $MgS{O}_4$.
Similarly, temporary hardness is due to bicarbonates of $Ca$ and $Mg$.