Hard water is not available for an experiment. Some salts are given below :
<br> (I) Sodium chloride
<br> (II) Sodium sulphate
<br> (III) Calcium chloride
<br> (IV) Calcium sulphate
<br> (V) Potassium chloride
<br> (VI) Magnesium sulphate
Select from the following group of these salts, each member of which may be dissolved in water to make it hard.
