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The correct increasing order of stability of the complexes based on Δo value is : (I) [Mn(CN)6]3− (II) [Co(CN)6]4− (III) [Fe(CN)6]4− (IV) [Fe(CN)6]3−

1. II < III < I < IV
2. IV < III < II < I
3. I < II < IV < III
4. III < II < IV < I

Correct answer: I < II < IV < III

Solution

The stability of the complexes is influenced by the strength of the ligand field, which is indicated by the Δo value. In this case, the order of increasing stability reflects the increasing ligand strength and the oxidation states of the metal ions, with [Fe(CN)6]3− being the most stable due to the strong field strength of CN⁻ ligands.

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