(a) What is meant by unidentate, bidentate and ambidentate ligands? Give two examples for each.
(b) Calculate the overall complex dissociation equilibrium constant for the `Cu(NH_3)_(4)^(2+)` ion, given that `beta4` for this complex is `2.1xx10^13`.

Explanation

(a) A molecule or an ion which has on]y one donor atom to form one coordinate bond with the central metal atom is called unidentate ligand, eg., `Cl^-and NH_3`. A molecule or an ion which contains two donor atoms and hence forms two coordinate bonds with the central metal atom is called a didentatc ligands, eg., `NH_2 -CH_2-CH_2 - NH_2 and overset(-)COC -COO` A molecule or an ion which contains two donor atoms but only of them forms a coordinate bond at a time with the centeral metal atom is called ambidentate ligand, ag, : `CN^-or NC :and : NO_2or : ONO^-`.
(b) (i) `Cu^(2+)+NH_3hArrCu(NH_3)^(2+)`
`k_1=([Cu(NH_3)]^(2+))/([Cu^(2+)][NH_3])`
(ii) `Cu(NH_3)^(2+)+NH_3hArrCu(NH_3)_(2^(2+))`
`k_2=([Cu(NH_3)_2]^(2+))/([Cu(NH_3)]^(2+)[NH_3])`
(iii) `beta_4=([Cu(NH_3)_4]^(2+))/([(NH_3)]^(4)[Cu^(2+)])`
`[beta_4=k_1xxk_2xxk_3xxk_4]`