Besides using carbon dioxide, encrustation can also be prevented by adding ______

Besides using carbon dioxide, encrustation can also be prevented by adding ______

• A. sodium hexametaphosphate
• B. sequestering agents
• C. citric acid
• D. muriatic acid

Answer: (A)

Encrustation occurs when calcium and magnesium precipitate as scale on surfaces, so the goal is to keep those hardness ions in solution. Besides using carbon dioxide to lower pH and shift carbonate equilibria, you can add a sequestrant that binds Ca2+ and Mg2+ to prevent precipitation. Sodium hexametaphosphate is a classic sequestrating agent used for this purpose; it forms stable complexes with the hardness ions, keeping them dissolved and stopping calcium carbonate from forming scale on pipes and equipment. While other options like citric acid can also act as chelants, the specific additive commonly used in water treatment to prevent encrustation is sodium hexametaphosphate. Muriatic acid would lower pH and isn’t a preventive scale-control measure, and sequestering agents is a category, but the question is pointing to a concrete agent, with sodium hexametaphosphate being the standard choice.

Encrustation occurs when calcium and magnesium precipitate as scale on surfaces, so the goal is to keep those hardness ions in solution. Besides using carbon dioxide to lower pH and shift carbonate equilibria, you can add a sequestrant that binds Ca2+ and Mg2+ to prevent precipitation. Sodium hexametaphosphate is a classic sequestrating agent used for this purpose; it forms stable complexes with the hardness ions, keeping them dissolved and stopping calcium carbonate from forming scale on pipes and equipment. While other options like citric acid can also act as chelants, the specific additive commonly used in water treatment to prevent encrustation is sodium hexametaphosphate. Muriatic acid would lower pH and isn’t a preventive scale-control measure, and sequestering agents is a category, but the question is pointing to a concrete agent, with sodium hexametaphosphate being the standard choice.