Permanent hardness of water is due to the presence of

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sulphates of sodium and potassium

sulphates of magnesium and calcium

carbonates of sodium and magnesium

bicarbonates of magnesium and calcium

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Answer is Wrong!

This question was previously asked in

UPSC NDA-1 – 2015

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Hardness of water is primarily caused by the presence of dissolved calcium and magnesium ions (Ca$^{2+}$ and Mg$^{2+}$). Temporary hardness is caused by their bicarbonates, which can be removed by boiling. Permanent hardness is caused by the presence of calcium and magnesium sulphates and chlorides, which are not removed by simple boiling.

Permanent hardness of water is due to the dissolved sulphates and chlorides of calcium and magnesium.

Sodium and potassium ions do not cause water hardness. Carbonates and bicarbonates of Ca and Mg cause temporary hardness. Permanent hardness needs chemical methods like ion exchange (using zeolite or synthetic resins) for removal.

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