Question

Differentiate between:
(i) Double salt and Complex compound
(ii) Didentate ligand and Ambidentate ligand

Answer 1

(i) Double Salts vs Complex Compounds

Double salts are ionic compounds formed by the combination of two simple salts, but they retain their individual identities in solution. These compounds do not involve coordinate bonds.

For example: \[ \mathrm{K_2SO_4 \cdot Al_2(SO_4)_3} \] is a double salt.

In contrast, complex compounds consist of a central metal ion bonded to ligands through coordinate covalent bonds. These ligands donate electron pairs to the metal.

Example of a complex compound: \[ [\mathrm{CoCl_2(en)_2}]SO_4 \] where "en" stands for ethylenediamine, a ligand.

(ii) Didentate vs Ambidentate Ligands

- Didentate ligands are ligands that can bind to a metal atom or ion through two donor atoms simultaneously. An example is ethylenediamine (en), which uses both nitrogen atoms to bind to the metal.

- Ambidentate ligands have two potential donor atoms, but can coordinate through only one atom at a time. A classic example is the thiocyanate ion: \[ \mathrm{SCN^-} \] It can bind to the metal via the sulfur atom (S-bound) or the nitrogen atom (N-bound), but not both at once.