EDTA is a hexadentate ligand containing four carboxylic acid groups and two amines.Which is true for the acid-base properties of EDTA?
I EDTA is a hexaprotic system,H₆Y²⁺,when the amines are protonated.
II Neutral EDTA,H₄Y,is tetraprotic when the amines are not protonated.
III Deprotonated EDTA,Y⁴⁻,is the only form of EDTA that binds to metal cations.
IV The fraction of EDTA in any of the six EDTA species is pH dependent.

Question

Quizplus · Accepted Answer

EDTA is indeed a hexaprotic system when considering all its protonatable sites, including the four carboxylic acids and the two amines, making statement I correct. Neutral EDTA without protonated amines can lose four protons from its carboxylic acid groups, making it tetraprotic, which confirms statement II. Statement III is incorrect because EDTA can bind to metal cations in various deprotonated forms, not just the fully deprotonated Y4- form. The ability of EDTA to bind metals is not limited to its fully deprotonated state. Finally, the fraction of EDTA in any of its protonation states indeed depends on the pH of the solution, making statement IV correct.

EDTA Is a Hexadentate Ligand Containing Four Carboxylic Acid Groups