Q106 / 270 · NDA 2025 (Phase 2) · General Ability

Which one of the following salts is responsible for temporary hardness of water?

  • A
    Sulphates of calcium
  • B
    Chlorides of magnesium
  • Correct answer
    C
    Bicarbonates of magnesium
  • D
    Sulphates of magnesium

Solution

Temporary hardness of water is caused by the presence of dissolved bicarbonates of calcium and magnesium, namely $Ca(HCO_3)_2$ and $Mg(HCO_3)_2$.

Permanent hardness of water is caused by the presence of dissolved chlorides and sulphates of calcium and magnesium.

Therefore, bicarbonates of magnesium are responsible for the temporary hardness of water.

Answer: Bicarbonates of magnesium

Hence, the correct answer is option: 'C'.

Relevant Questions