Question

In the neighborhood of your school, hard water required for an experiment is not available. Select from the following groups of salts available in your school, a group each member of which, if dissolved in distilled water, will make it hard:
A: sodium chloride, calcium chloride
B: potassium chloride, sodium chloride
C: sodium chloride, magnesium chloride
D: calcium chloride, magnesium chloride

Answer 1

Hint: Naturally occurring water is soft water. But presence of some salts and minerals makes the soft water hard. Soft water becomes hard after coming in contact with ground. Hardness of water is measured in parts per million.

Complete step by step answer:
In this question we have to find the salts which will make distilled water hard. Distilled water is soft water. When some salts will be dissolved in distilled water distilled water will become hard. Hardness of water is due to the presence of calcium and magnesium salts. Calcium and magnesium salts are the main reason for the hardness in water. As the amount of these salts in water increases, the hardness of the water increases. Chlorides, bicarbonates and sulphates of calcium and magnesium make water hard. So, we have to find the option with salts of calcium and magnesium. In option D calcium chloride and magnesium chloride is given.

This means the correct answer is option D.

Additional information: Hard water can’t be used in the sugar industry. Water containing salts causes difficulties in crystallization of sugar. This is why hard water is not suitable in the sugar industry.
Hard water can’t be used in the paper industry as calcium and magnesium salts can react with the chemicals that are used to make the paper smooth.

Note:
Boiling point of any substance increases in the presence of impurities. In hard water calcium and magnesium salts are present. These salts act as impurities. Due to these impurities the boiling point of water is increased. Due to which more fuel is required to boil water.