The crystal field splitting energy of [Co(oxalate)3]3− complex is n times that of the [Cr(oxalate)3]3− complex
Q. The crystal field splitting energy of [Co(oxalate)3]3− complex is 'n' times that of the [Cr(oxalate)3]3− complex. Here 'n' is ____ . (Assume Δ0 ≫ P)
Correct Answer: 2

Explanation

Both complexes, [Co(oxalate)3]3− and [Cr(oxalate)3]3−, are octahedral complexes with the same ligand (oxalate).

Hence, the crystal field splitting energy Δ0 depends mainly on the oxidation state and nature of the metal ion.

The oxidation states are:

Cr in [Cr(oxalate)3]3− → Cr³⁺
Co in [Co(oxalate)3]3− → Co³⁺

Both Cr³⁺ and Co³⁺ belong to the 3d series, but Co³⁺ has a higher effective nuclear charge than Cr³⁺.

For octahedral complexes with the same ligand:

Δ0 ∝ oxidation state of metal ion

Since Co³⁺ has a greater tendency to split d-orbitals compared to Cr³⁺, the crystal field splitting energy of the cobalt complex is approximately twice that of the chromium complex.

Therefore,

n = 2

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