The Chelating ligand used for the estimation of hardness of water is .....
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → EDTA
A chelating ligand binds a metal ion through two or more donor atoms at the same time and forms rings with it, which makes the complex very stable. EDTA (ethylenediaminetetraacetate) is a hexadentate ligand: it binds through two nitrogen atoms and four carboxylate oxygen atoms.
The hardness of water is due to \( \ce{Ca^2+} \) and \( \ce{Mg^2+} \) ions, which EDTA holds as 1 : 1 chelates:
\( \displaystyle \ce{Ca^2+ + EDTA^4- -> [Ca(EDTA)]^2-} \)
NCERT (2026-27 edition):
Importance and Applications of Coordination Compounds – …
