Question

Alum helps in purifying water by

• A. forming Si complex with clay particles
• B. sulphate part, which combines with the dirt and removes it
• C. aluminium ion, which coagulates the mud particles
• D. making mud water soluble

Answer 1

The correct option is C aluminium ion, which coagulates the mud particles

Alum, also known as aluminium sulfate is added to water in order to destabilize the mud particles suspended in it. This process is known as coagulation.

Alum helps in purifying water by aluminium which coagulates the mud particles. Because of the high charge on the aluminium ion (Al+3), it helps the small particles of suspended solids to group together until they are of such size that they sink and can be removed.

Hence, option (C) is correct.