The precipitative softening process uses _____ that render _______ calcium and magnesium ______

The precipitative softening process uses _____ that render _______ calcium and magnesium ______

• A. Chemical reactions, colloidal, to precipitate
• B. Physical processes, dissolved, insoluble
• C. Chemical reactions, dissolved, insoluble
• D. Physical processes, colloidal, to precipitate

Answer: (C)

Precipitative softening relies on chemical reactions that transform dissolved hardness ions into insoluble solids that can be removed from the water. When lime or lime-soda ash is added, calcium and magnesium ions in solution react to form insoluble compounds such as calcium carbonate and magnesium hydroxide. These precipitates settle out and can be filtered or allowed to sediment, reducing water hardness. This is a chemical change, not a physical separation of colloids, and the ions start in dissolved form, not already as solids.

Precipitative softening relies on chemical reactions that transform dissolved hardness ions into insoluble solids that can be removed from the water. When lime or lime-soda ash is added, calcium and magnesium ions in solution react to form insoluble compounds such as calcium carbonate and magnesium hydroxide. These precipitates settle out and can be filtered or allowed to sediment, reducing water hardness. This is a chemical change, not a physical separation of colloids, and the ions start in dissolved form, not already as solids.