A chelating agent exchanges another ion for the calcium ion.

• A. True
• B. False
• C. It exchanges calcium for magnesium
• D. It exchanges all ions

Answer: (B)

A chelating agent works by binding metal ions through multiple donor atoms to form a stable metal–ligand complex. It removes the ion from the surrounding environment by tight binding, not by swapping it with another ion. For example, EDTA binds Ca2+ to form a soluble calcium–EDTA complex, gradually demineralizing without exchanging calcium for magnesium or any other ion. Ion-exchange, on the other hand, involves swapping ions on a resin, which is a different mechanism. So the statement that a chelating agent exchanges another ion for the calcium ion is not correct.