Pipe-borne water is usually chlorinated in order to

Step 1: Analyze the question The question asks why chlorine is added to pipe-borne (tap) water during treatment.

Step 2: The concept Water treatment has several stages, each with its own purpose:

• Sedimentation and coagulation: alum (aluminium sulphate) is added to make suspended particles clump together and settle.
• Filtration: removes the remaining solid particles.
• Chlorination: chlorine is added as a disinfectant. It kills disease-causing microorganisms such as the bacteria that cause cholera, typhoid and dysentery.
• Removal of hardness: done by methods like boiling (temporary hardness), adding washing soda, or ion exchange (e.g. permutit), not by chlorine.

Step 3: Check each option

• A. Coagulate sediments: this is the job of alum, not chlorine. ✗
• B. Improve taste: chlorine can leave a taste, and this is not its main purpose. ✗
• C. Kill harmful bacteria: this is the main purpose of chlorination. ✓
• D. Make it pure: chlorinated water is safe to drink, but it is not chemically pure because it still contains dissolved substances. ✗
• E. Remove hardness: chlorine does not remove Ca²⁺ or Mg²⁺ ions. ✗

Step 4: Answer The correct option is C. kill harmful bacteria in the water.

Exam tip: Match each treatment to its job:

• Alum → makes particles settle
• Filter → removes solids
• Chlorine → kills germs

Be careful with the word "pure" in options. In chemistry, treated water is safe to drink but not pure.