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Question: Answered & Verified by Expert
In which of the following octahedral complex species the magnitude of $\Delta_0$ will be maximum?
ChemistryCoordination CompoundsJEE MainJEE Main 2013 (25 Apr Online)
Options:
  • A
    $\left[\mathrm{Co}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+}$
  • B
    $\left[\mathrm{Co}(\mathrm{CN})_6\right]^{3-}$
  • C
    $\left[\mathrm{Co}\left(\mathrm{C}_2 \mathrm{O}_4\right)_3\right]^{3-}$
  • D
    $\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_6\right]^{3+}$
Solution:
2328 Upvotes Verified Answer
The correct answer is:
$\left[\mathrm{Co}(\mathrm{CN})_6\right]^{3-}$
Crystal field splitting depends upon the nature of ligand. The nature of ligand $\Delta$ decreases as shown below
$\mathrm{C}_2 \mathrm{O}_4^{--} < \mathrm{H}_2 \mathrm{O} < \mathrm{NH}_3 < \mathrm{CN}^{-}$
hence the crystal field splitting will be maximum for $\left[\mathrm{Co}(\mathrm{CN})_6\right]^{3-}$

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