Question

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

Answer 1

(i) Double Salt vs. Complex Compound

Double Salt:

• A double salt is formed by the crystallization of two simple salts together in a definite stoichiometric ratio.
• They retain individual salt properties in the solid state and dissociate completely into ions in aqueous solution.
• Example: \({K2SO4 \cdot Al2(SO4)3 \cdot 24H2O}\) (Potash alum)

Complex Compound:

• Complex compounds consist of a central metal ion bonded to ligands via coordinate covalent bonds.
• They do not dissociate into simple ions entirely; the complex ion remains intact in solution.
• Example: \({[Cu(NH3)4]SO4}\)

Quick Tip:
Double salts consist of multiple simple salts and dissociate into ions in solution, whereas complex compounds contain stable metal-ligand coordination structures that behave as single species in solution.

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(ii) Didentate Ligand vs. Ambidentate Ligand

Didentate Ligand:

• Has two donor atoms capable of simultaneously coordinating to the same metal ion.
• Forms two coordinate bonds with the metal center.
• Example: Ethylenediamine (en), \({H2NCH2CH2NH2}\)

Ambidentate Ligand:

• Has two potential donor atoms, but only one binds at a time to the metal center.
• Example: Thiocyanate ion (\({SCN^-}\)), which can bind through sulfur (\({S}\)) or nitrogen (\({N}\)) atom.