RPSC LECTURER – 2011
⭕ A. Hardness of water
⭕ B. Acidity of water
⭕ C. Carbonates in water
⭕ D. Sulphates in water
📚 Explanation:
Alum (Aluminium sulfate) is widely used as a coagulant in water treatment plants.
When alum dissolves in water, it undergoes hydrolysis and produces:
🔹 Sulfuric acid (a weak acid)
🔹 Aluminium hydroxide flocs
Because of this reaction, the acidity of water increases (i.e., pH decreases).
Alum is preferred because it is:
🔹 Efficient
🔹 Economical
🔹 Produces good-quality flocs for sedimentation
Alum (Aluminium sulfate) is widely used as a coagulant in water treatment plants.
When alum dissolves in water, it undergoes hydrolysis and produces:
🔹 Sulfuric acid (a weak acid)
🔹 Aluminium hydroxide flocs
Because of this reaction, the acidity of water increases (i.e., pH decreases).
Alum is preferred because it is:
🔹 Efficient
🔹 Economical
🔹 Produces good-quality flocs for sedimentation
👉 Therefore, the correct answer is: B. Acidity of water
Key Points on Alum in Water Treatment:
- Alum reacts with water: Forms acidic products, lowering pH.
- Used as coagulant: Helps in removing suspended impurities.
- Cheap & effective: One of the most commonly used coagulants.
