The Langelier Saturation Index is used to assess the tendency of water to precipitate or dissolve calcium carbonate.

• A. Dissolve Organic Matter
• B. Precipitate Calcium Carbonate
• C. Taste and Odor
• D. Remove Metals

Answer: (A)

The main idea here is how Langelier Saturation Index predicts the behavior of calcium carbonate in water. The LSI tells whether water is in a state that favors calcium carbonate forming a solid scale or dissolving away as a dissolved substance. If the water is supersaturated with calcium carbonate, it tends to precipitate CaCO3 and form scale on pipes and equipment. If it’s undersaturated, calcium carbonate will dissolve from surfaces, contributing to corrosive conditions and mineral loss. So the concept being tested is the tendency of water to precipitate or dissolve calcium carbonate. The option that describes calcium carbonate precipitation matches what the LSI is used to indicate, while the other choices describe aspects (organic matter, taste/odor, metals removal) that aren’t what the Langelier Index assesses.