Which one of the following salts is responsible for temporary hardness of water?
- A.Sulphates of calcium
- B.Chlorides of magnesium
- C.Bicarbonates of magnesium
- D.Sulphates of magnesium
Show answer
Temporary hardness is caused by the bicarbonates (hydrogencarbonates) of calcium and magnesium dissolved in water. It is called temporary because it can be removed simply by boiling: on heating, the soluble bicarbonates break down into insoluble carbonates, or magnesium hydroxide, which settle out, and carbon dioxide escapes.
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