The concentration of Ca2+ in hard water can be determined by titration with a reagent X which forms a complex with Ca2+ giving a change in colour. Since the colour change is sensitive to pH, the titration has to be carried out in an alkaline buffer.
Th structure of X is similar to that of an amino acid. The way X acts as a ligand can be understood by considering how aminoethanoic acid forms co-ordinate bonds with a calcium ion.
Explain why the complex between aminoethanoic acid and aqueous calcium ions is more stable at pH 10 than at pH 4.
The Attempt at a Solution
I really have no idea how pH would affect the dative bonding.