Question

Hard water required for an experiment is not available in a school laboratory. However, following salts are available in the laboratory. Select the salts which may be dissolved in water to make it hard for the experiment.

(1)	Calcium Sulphate	(2)	Sodium Sulphate
(3)	Calcium Chloride	(4)	Potassium Sulphate
(5)	Sodium Hydrogen Carbonate	(6)	Magnesium Chloride

(A) 1, 2 and 4

(B) 1, 3 and 6

(C) 3, 5 and 6

(D) 2, 4 and 5

Answer 1

(B)
Hard water contains Ca²⁺ and Mg²⁺ ions. So the salts that can be added to water to make it hard are calcium sulphate, calcium chloride and magnesium chloride.