Question

Explain the following:

Muddy water can be purified by adding potash alum to it.

Answer 1

Muddy water contains tiny suspended particles (colloidal impurities) that do not settle easily. When potash alum is added to muddy water, it dissociates to release Al³⁺ ions. These Al³⁺ ions are positively charged and neutralize the negative charges on the colloidal particles. This causes the particles to coagulate or clump together into larger aggregates. The larger aggregates settle down or can be removed by filtration, making the water clear and purified. This process is called coagulation, and potash alum acts as a coagulant to remove the suspended impurities from water effectively.