Question

Which one of the following processes will produce hard water ?

• A. Saturation of water with $CaC{O}_3$
• B. Saturation of water with $MgC{O}_3$
• C. Saturation of water with $MgS{O}_4$
• D. none of the above

Answer 1

The correct option is C Saturation of water with $MgS{O}_4$

$MgC{O}_3$ and $CaC{O}_3$ are water-insoluble. $CaS{O}_4$ dissolves in water adding $C{a}^{2+}$ ions which are responsible for producing hardness in water. Hence saturation of ordinary water with $CaS{O}_4$ produces hard water.