Question

Alum is widely used to purify water since :

• A. it forms complex with clay particles
• B. it coagulates the mud particles
• C. it exchanges $C{a}^{2+}$ and $M{g}^{2+}$ ions present in hard water
• D. its sulphate ion is water purifier

Answer 1

Answer: (B)

Mud is colloidal charged solution which on treatment with alum $(A{l}^{3+})$ gets neutralised or coagulated.