In the octahedral crystal field, the correct order of splitting in $\mathrm{Cr}^{3+}$ complexes for $\mathrm{I}^{-}, \mathrm{H}_2 \mathrm{O}, \mathrm{NH}_3$ and $\mathrm{CN}^{-}$is

• A

  $\mathrm{CN}^{-} < \mathrm{NH}_3 < \mathrm{H}_2 \mathrm{O} < \mathrm{I}^{-}$
• B

  $\mathrm{NH}_3 < \mathrm{H}_2 \mathrm{O} < \mathrm{I}^{-} < \mathrm{CN}^{-}$
• C

  $\mathrm{CN}^{-} < \mathrm{I}^{-} < \mathrm{H}_2 \mathrm{O} < \mathrm{NH}_3$
• Correct answer
  D

  $I^{-} < \mathrm{H}_2 \mathrm{O} < \mathrm{NH}_3 < \mathrm{CN}^{-}$

Solution

$\because$ Order of crystal field splitting for the ligands in $\mathrm{Cr}^{3+}$ is
Hence, correct order is $\mathrm{I}^{-} < \mathrm{H}_2 \mathrm{O} < \mathrm{NH}_3 < \mathrm{CN}^{-}$and option (d) is the correct answer.

Hence, the correct answer is option: 'D'.