Which of the following salt when dissolved, makes the water hard?
(A) Sodium Bicarbonate.
(B) Magnesium Bicarbonate.
(C) Potassium Nitrate.
(D) Sodium Chloride.
Answers
Answer:
Answer is B [Magnesium Bicarbonate]
Explanation:
When either calcium sulphate, or magnesium bicarbonate or calcium chloride is dissolved in water, hard water is obtained. Hard water is due to presence of sulpahtes, chlorides or bicarbonates of magnesium and calcium in water.
Sodium carbonate, Na2 CO3 , is also known asаwashing soda. It can remove temporary and permanent hardness from water. Sodium carbonate is soluble but calcium carbonate and magnesium carbonate are insoluble. The water is softened because it no longer contains dissolved calcium ions and magnesium ions. The calcium, magnesium and iron(II) ions cause 'hardness', that is they stop the lathering that should be apparent in the distilled water and the other test tubes. Intermediate students should be able to track the cause of hardness down to these cations and say that the anions make no difference. Hardness is caused by compounds of calcium and magnesium, and by a variety of other metals. ... Water is a great solvent for calcium and magnesium, so if the minerals are present in the soil around a water-supply well, hard water may be delivered to homes. Water hardness is mainly caused by calcium and magnesium salts. It is also caused by iron aluminum and other metals but only to an extent. These causes are very little. Water hardness that is caused by bicarbonates and carbonates from the calcium and magnesium are called temporary hardness.