devarshi-dt-logo

Question:

A student requires hard water for an experiment in his laboratory which is not available in the neighbouring area. In the laboratory there are hard water. Select from the following groups of salts, a group, each salt of which when dissolved in distilled water will make it hard. Sodium chloride, Potassium chloride; Sodium sulphate, Potassium sulphate; Sodium sulphate, Calcium sulphate; Calcium sulphate, Calcium chloride

Sodium chloride, Potassium chloride

Sodium sulphate, Potassium sulphate

Sodium sulphate, Calcium sulphate

Calcium sulphate, Calcium chloride

Solution:

If hard water is not available it can be made in the laboratory by dissolving a little of calcium salt or magnesium salt in a beaker of water. The calcium and magnesium salts that can be used here are: calcium hydrogen carbonate, calcium sulphate, calcium chloride, magnesium hydrogen carbonate, magnesium sulphate or magnesium chloride.