Which of the following statements about EDTA are correct:
(A) It is a hexadentate ligand.
(B) It is used to treat tumors.
(C) It forms chelate complexes.
(D) It is used in the estimation of Mg2+ and Ca2+ ions in hard water.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (A), (C) and (D) only
EDTA (ethylenediaminetetraacetate ion, EDTA4−) has two nitrogen atoms and four carboxylate oxygen atoms that can each donate a lone pair to the same metal ion. A ligand that binds through several donor atoms wraps round the metal and forms rings; such complexes are called chelates and are especially stable.
(A) It is a hexadentate ligand. — Correct. 2 N + 4 O = 6 donor atoms.
(B) It is used to treat tumors. — Incorrect. Tumours are treated with platinum complexes such as cis-platin, \( \ce{[Pt(NH3)2Cl2]} \). EDTA is used medically in the treatment of lead poisoning.
(C) It forms chelate complexes. — Correct. Binding through six donor atoms gives several five-membered chelate rings.
(D) It is used in the estimation of \( \ce{Mg^{2+}} \) and \( \ce{Ca^{2+}} \) ions in hard water. — Correct. Hardness of water is estimated by titration with Na2EDTA, which forms stable complexes with \( \ce{Ca^{2+}} \) and \( \ce{Mg^{2+}} \).
NCERT (2026-27 edition):
Definitions of Some Important Terms Pertaining to Coordination Compounds – “… Ethylenediaminetetraacetate ion (EDTA4–) is an important hexadentate ligand. It can bind through two nitrogen and four oxygen atoms to a central metal ion.”
Importance and Applications of Coordination Compounds – “… Hardness of water is estimated by simple titration with Na2EDTA. … An example is the treatment of problems caused by the presence of metals in toxic proportions in plant/animal systems. Thus, excess of copper and iron are removed by the chelating ligands D–penicillamine and desferrioxime B via the formation of coordination compounds. EDTA is used in the treatment of lead poisoning. Some coordination compounds of platinum effectively inhibit the growth of tumours. Examples are: cis–platin and related compounds.”