Coordination Compounds

Step 1: Checking for optical isomerism.
- Optical isomerism occurs in complexes with chiral centers or asymmetric arrangements.
- Cis-[CrCl (C O ) ] can show optical isomerism due to asymmetric bidentate ligands.
- [PtCl (en) ] and [Co(en) ] also show optical isomerism.
- [Co(NH ) (NO ) ] lacks asymmetry and does not exhibit optical isomerism.

Step 1: Magnetic Moment Formula The spin-only magnetic moment ( ) is given by: where is the number of unpaired electrons.

Step 2: Analyzing - Mn in is in the +3 oxidation state ( ). - is a strong field ligand, causing pairing of electrons, leaving .

Step 3: Analyzing - Co in is in the +3 oxidation state ( ). - is a strong field ligand, leading to full pairing of electrons ( ).

Acidification of chromate (CrO ) leads to the formation of dichromate (Cr O ).
The reaction is:
2CrO + 2H → Cr O + H O The 'Z' in this reaction is dichromate (Cr O ).
To find the oxidation state of chromium in Cr O , let the oxidation state of Cr be x.
2x + 7(-2) = -2
2x - 14 = -2
2x = 12
x = +6
Therefore, the oxidation state of chromium in dichromate is +6.

I.

Mn is in +3 oxidation state. Mn has configuration. CN is a strong field ligand, so it causes pairing. The electron configuration for with pairing is:

. The number of unpaired electrons is 2. Magnetic moment BM, where is the number of unpaired electrons. BM.

II.

Mn is in +3 oxidation state. Mn has configuration. Cl is a weak field ligand, so pairing does not occur. The electron configuration for without pairing is:

. The number of unpaired electrons is 4. Magnetic moment BM. BM.

III.

Fe is in +3 oxidation state. Fe has configuration. CN is a strong field ligand, so it causes pairing. The electron configuration for with pairing is:

. The number of unpaired electrons is 1. Magnetic moment BM. BM.

IV.

Fe is in +3 oxidation state. Fe has configuration. F is a weak field ligand, so pairing does not occur. The electron configuration for without pairing is:

. The number of unpaired electrons is 5. Magnetic moment BM. BM.

Arranging in increasing order of magnetic moments:

III I II IV.