Question
Which one of the following processes will produce hard water?
A.
Saturation of water with $$MgC{O_3}$$
B.
Saturation of water with $$CaS{O_4}$$
C.
Addition of $$N{a_2}S{O_4}$$ to water
D.
Saturation of water with $$CaC{O_3}$$
Answer :
Saturation of water with $$CaS{O_4}$$
Solution :
Permanent hardness of water is due to chlorides and sulphates of calcium and magnesium i.e $$CaC{l_2},CaS{O_4},MgC{l_2}\,{\text{and}}\,MgS{O_4}$$