Question
How does the addition of alum purify water?
Solution
Answer:
When alum (Al2(SO4)3 is added into water. It forms a gel like precipitate such as Al(OH)3 . The alum precipitate then forms small bundles that trap suspended particles as they fall through water.
This process is known as floculation.
After floculation the particles will be large enough to settle and can be removed.
