Coordination Compounds

Question 1

Postulates of Werner’s theory

Answer 1

• Central metal ion shows two types of linkages or valencies
• Primary valency is ionisable, satisfied by anions
• Secondary valency is non ionisable, satisfied by neutral molecules or anions (ligands)
• Spatial arrangement of ligands around central metal ion is called polyhedron.

Question 2

Carnallite

Answer 2

KCl.MgCl₂.6H₂O

Question 3

Mohr’s salt

Answer 3

FeSO₄.(NH₄)₂SO₄.6H₂O

Question 4

Potash alum

Answer 4

K₂SO₄.Al₂(SO₄)₃.24H₂O

Question 5

NH3 can act as strong ligand with

Answer 5

Co

Question 6

Postulates of VBT

Answer 6

• Central metal atom or ion makes available vacant orbitals equal to its coordination number.
• Orbitals may be inner orbitals or outer orbitals depending on strength of ligand.
• Vacant orbitals undergo hybridisation.
• Hybrid orbitals overlap with ligand orbitals that can donate electron pair.

Question 7

Postulates of CFT

Answer 7

• Metal-ligand bond arises as a result of electrostatic attraction between metal and ligand.
• Anionic ligands are considered to be point charges while neutral ligands are considered as dipoles.
• As the ligand approaches the central metal atom or ion, the field around the metal becomes unsymmetrical and degeneracy is disturbed resulting in splitting of orbitals.
• Splitting of orbitals depends on nature of ligand and crystal field.

Question 8

Order of strong field ligands in spectrochemical series

Answer 8

CO- > CN- > en > NH3 > EDTA4-

Question 9

Limitations of CFT

Answer 9

• If ligands are point charges, anionic ligands should show more splitting but they are actually found at lower end of the electrochemical series.
• It considers metal-ligand bond to be purely ionic, does not account for covalent character.