Question

Alum is a water purifier because it:

• A. coagulates the impurities
• B. softens hard water
• C. gives taste
• D. destroys the pathogenic bacteria

Answer 1

Answer: (A)

coagulates the impurities

Alum is a water purifier because it coagulates the impurities. The colloidal particles are negatively charged and alum is added as a coagulant to create positively charged ions. Once the repulsive charges have been neutralized, the van der Waals force will cause the particles to combine together and will result in coagulation.