The complex formed by Ca2+ with EDTA is more stable than the complex formed by Ca2+ with ethylene diamine.

Question

Give reason for the following: 

(a) The complex formed by Ca²⁺ with EDTA is more stable than the complex formed by Ca²⁺ with ethylene diamine. 

(b) In d⁴ complexes, ligands for which ∆_o < P ,form high spin complexes. 

(c) On removal of water from [Ti(H₂O)₆ ]Cl₃ on heating, it become colourless.

Answer 1

(a) EDTA is a hexadentate ligand while ethylene diamine is bidentate, the chelating effect of EDTA is more therefore EDTA-Ca2+ complex is more stable. 

(b) If ∆_o < P, the fourth electron enters one of the eg orbitals giving the configuration t_2g³e_g ¹ 

(c ) On heating water molecule which is acting as ligand is lost .In the absence of ligand, crystal field splitting does not occur so there is no d-d transition and hence the substance is colourless