Which of the following is suitable for removing both temporary and permanent hardness?

Kingsley Thompson January 20, 2026

Which of the following is suitable for removing both temporary and permanent hardness?

A. the addition of alum

B. the addition of Ca(OH)2

C. distillation

D. boiling

Temporary hardness is caused by bicarbonates of calcium and magnesium, while permanent hardness is caused by their sulphates and chlorides.

Let’s check each option:

  • A. Addition of alum
    Alum is used for coagulation (removing suspended particles), not hardness ❌

  • B. Addition of Ca(OH)₂ (slaked lime)
    Lime removes temporary hardness only, not permanent hardness ❌

  • C. Distillation
    Distillation removes all dissolved salts, therefore removes both temporary and permanent hardness ✅

  • D. Boiling
    Boiling removes temporary hardness only ❌

✅ Correct answer: C. distillation

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Kingsley Thompson

Posted by: Kingsley Thompson

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