Question
Explain the chemical phenomenon involved in the purification of water using potash alum.
Solution
Answer:
The purification of water involves the coagulation (precipitation) of suspended colloidal particles of clay, sand etc., by the addition of potash alum. Alum gives Al3+ ions in water, which discharge the negatively charged dirt or clay particles suspended in water, causing them to coagulate.
Further Al2(SO4)3 present in alum is partly hydrolysed by water to give colloidal Al(OH)3which absorbs the suspended particles also.
The purification of water involves the coagulation (precipitation) of suspended colloidal particles of clay, sand etc., by the addition of potash alum. Alum gives Al3+ ions in water, which discharge the negatively charged dirt or clay particles suspended in water, causing them to coagulate.
Further Al2(SO4)3 present in alum is partly hydrolysed by water to give colloidal Al(OH)3which absorbs the suspended particles also.
