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Difficulty: MediumPurification and Treatment of Water for Supply

During domestic water treatment, a household adds a measured amount of calcium hypochlorite (bleaching powder) to clear well water before consumption. What is the primary chemical purpose of adding this substance?

  1. To destroy pathogenic microorganisms present in the waterAnswer
  2. B
    To precipitate dissolved calcium and magnesium ions that cause hardness
  3. C
    To coagulate fine suspended clay particles into larger settles
  4. D
    To neutralize organic tastes and unpleasant odors in the water

Answer

Adding calcium hypochlorite serves to sterilize the water by killing pathogenic bacteria and microorganisms.
Calcium hypochlorite (Ca(ClO)2Ca(ClO)_2) releases hypochlorous acid and chlorine when added to water. This powerful oxidizing environment kills bacteria, viruses, and other disease-causing pathogens, fulfilling the sterilization stage of water treatment.

Step-by-Step Solution

1
Identify the chemical reagent and its functional group
Calcium hypochlorite, Ca(ClO)2Ca(ClO)_2, acts as a chlorine-releasing disinfecting agent.
Bleaching powder hydrolyzes in water to release active chlorine ions.
2
Distinguish municipal/domestic water treatment roles
Disinfection/sterilization kills microorganisms, whereas coagulation removes turbidity and precipitation removes hardness.
Each water treatment reagent plays a specific, distinct chemical role.

Key Concept

Chemical Sterilization in Water Purification
Estimated Time:1m 0s
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Topics

Purification and Treatment of Water for Supply

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