Question:
Identify the pair of chlorides responsible for permanent hardness of water.
Identify the pair of chlorides responsible for permanent hardness of water.
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Permanent hardness is due to chlorides and sulphates of calcium and magnesium, such as \(CaCl_2\), \(MgCl_2\), \(CaSO_4\), and \(MgSO_4\).
Updated On: May 7, 2026
- \(NaCl,\ KCl\)
- \(CaCl_2,\ KCl\)
- \(AlCl_3,\ MgCl_2\)
- \(MgCl_2,\ CaCl_2\)
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The Correct Option is D
Solution and Explanation
Hardness of water is caused by salts of calcium and magnesium.
Temporary hardness is mainly due to bicarbonates of calcium and magnesium.
Permanent hardness is caused by chlorides and sulphates of calcium and magnesium.
The common chloride salts responsible for permanent hardness are:
\[
CaCl_2
\]
and
\[
MgCl_2.
\]
These salts remain dissolved in water and cannot be removed simply by boiling.
Therefore, the pair of chlorides responsible for permanent hardness is:
\[
MgCl_2,\ CaCl_2.
\]
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