Multiple choice

Which is used for settling muddy water?

  1. Common salt

  2. Common alum

  3. Aluminium powder

  4. Bleaching powder

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Alum (aluminum sulfate) is used as a coagulant in water treatment - it neutralizes charges on suspended particles, causing them to clump together and settle out. Common salt does not cause coagulation, while bleaching powder is for disinfection.