Which statements about hardness of water are correct?

APermanent hardness is caused by chlorides and sulphates of calcium and magnesium and is not removed by boiling.
BHardness in ppm of $CaCO X_{3}$ means the mass of $Ca X^{2 +}$ ions present per million parts of water.
CTemporary hardness can be removed by boiling or by Clark's process (addition of lime).
DThe EDTA titration at pH 10 with EBT gives the total hardness ( $Ca X^{2 +}$ plus $Mg X^{2 +}$ ).

Answer: A, C, D

Boiling or lime removes the bicarbonates (temporary hardness) as insoluble carbonates/hydroxides, while chlorides and sulphates remain. EDTA at pH 10 complexes both

Ca X^{2 +}

and

Mg X^{2 +}

. Hardness in ppm of

CaCO X_{3}

is the equivalent mass of

CaCO X_{3}

that would have the same amount of hardness-causing ions, not the mass of

Ca X^{2 +}

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Which statements about hardness of water are correct?

Answer: A, C, D

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