The correct answer is: Alum as a coagulant is found to be most effective when pH range of water is 6 to 8.
Alum is a chemical compound with the formula Al2(SO4)3·14H2O. It is a white, water-soluble solid that is commonly used as a coagulant in water treatment. Coagulation is the process of causing particles in a suspension to clump together and settle out of the water. Alum is effective at this because it has a positive charge, which attracts negatively charged particles in the water. When these particles clump together, they form larger particles that are more easily removed from the water.
The pH of water is a measure of its acidity or alkalinity. A pH of 7 is neutral, a pH below 7 is acidic, and a pH above 7 is alkaline. The pH of water can affect the effectiveness of alum as a coagulant. In general, alum is most effective at pH values between 6 and 8. This is because the positive charge of alum is most effective at attracting negatively charged particles at these pH values.
At pH values below 6, the negative charge of the water molecules is stronger than the positive charge of the alum. This makes it more difficult for the alum to attract and coagulate the particles in the water. At pH values above 8, the positive charge of the water molecules is weaker than the positive charge of the alum. This also makes it more difficult for the alum to attract and coagulate the particles in the water.
Therefore, the pH range of 6 to 8 is the most effective for using alum as a coagulant.