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JEE Advanced 2025Paper 1
Exam
JEE Advanced
Year
2025
Paper
Paper 1
Subject
Chemistry
Chapter
Coordination Compounds

JEE Advanced 2025 · Paper 1 · Chemistry · Coordination Compounds

The correct order of the wavelength maxima of the absorption band...

The correct order of the wavelength maxima of the absorption band in the ultraviolet-visible region for the given complexes is

Options

  1. A[Co(CN)6]3−<\left[\mathrm{Co}(\mathrm{CN})_6\right]^{3-} <\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_6\right]^{3+} <\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_5\left(\mathrm{H}_2 \mathrm{O}\right)\right]^{3+} <\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_5(\mathrm{Cl})\right]^{2+}
  2. B[Co(NH3)5(Cl)]2+<\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_5(\mathrm{Cl})\right]^{2+} <\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_5\left(\mathrm{H}_2 \mathrm{O}\right)\right]^{3+} <\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_6\right]^{3+} <\left[\mathrm{Co}(\mathrm{CN})_6\right]^{3-}
  3. C[Co(CN)6]3−<\left[\mathrm{Co}(\mathrm{CN})_6\right]^{3-} <\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_5(\mathrm{Cl})\right]^{2+} <\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_5\left(\mathrm{H}_2 \mathrm{O}\right)\right]^{3+} <\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_6\right]^{3+}
  4. D[Co(NH3)6]3+<\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_6\right]^{3+} <\left[\mathrm{Co}(\mathrm{CN})_6\right]^{3-} <[Co(NH3)5(Cl)]2+<[Co(NH3)5(H2O)]3+\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_5(\mathrm{Cl})\right]^{2+} <\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_5\left(\mathrm{H}_2 \mathrm{O}\right)\right]^{3+}

Correct answer

A. [Co(CN)6]3−<\left[\mathrm{Co}(\mathrm{CN})_6\right]^{3-} <\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_6\right]^{3+} <\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_5\left(\mathrm{H}_2 \mathrm{O}\right)\right]^{3+} <\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_5(\mathrm{Cl})\right]^{2+}

Step-by-step solution

ΔO∝1λ\Delta_{\mathrm{O}} \propto \frac{1}{\lambda}∴ The  absorb wave length order is [Co(CN)6]3−<[Co(NH3)6]3+<[Co(NH3)5H2O]3+<[Co(NH3)5Cl]2+\begin{aligned} &\therefore \text{\text{ The } absorb wave length order is }\\ &\left[\mathrm{Co}(\mathrm{CN})_6\right]^{3-} <\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_6\right]^{3+} <\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_5 \mathrm{H}_2 \mathrm{O}\right]^{3+} <\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_5 \mathrm{Cl}\right]^{2+} \end{aligned}$$
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