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Question: Answered & Verified by Expert
The wavelength of light absorbed is highest in
ChemistryCoordination CompoundsAIIMSAIIMS 2011
Options:
  • A $\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_5 \mathrm{Cl}^{2+}\right.$
  • B $\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_5 \mathrm{H}_2 \mathrm{O}\right]^{3+}$
  • C $\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_6\right]^{3+}$
  • D $\left[\mathrm{Co}(\mathrm{en})_3\right]^{3+}$
Solution:
2873 Upvotes Verified Answer
The correct answer is: $\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_5 \mathrm{Cl}^{2+}\right.$
As in complex $\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_5 \mathrm{Cl}\right]^{2+}$ unpaired electrons are present, so it requires less energy for excitation. Thus, the wavelength of light absorbed will be highest (i.e., $E \propto 1 / \lambda$ ).

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