A student requires hard water for an experiment in his laboratory which is not available in the neighbouring area. In the laboratory there are some salts, which when dissolved in distilled water can convert it into hard water. Select from the following groups of salts, which when dissolved in distilled water will make it hard.
(a) Sodium chloride, Potassium chloride
(b) Sodium sulphate, Potassium sulphate
(c) Sodium sulphate, Calcium sulphate
(d) Calcium sulphate, Magnesium chloride

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

Select from the following group of these salts which may be dissolved in water to make it hard.

(I) Sodium chloride
(II) Sodium sulphate
(III) Calcium chloride
(IV) Calcium sulphate
(V) Potassium chloride
(VI) Magnesium sulphate