JEE Advanced 2025 Chemistry question
The correct order of the wavelength maxima of the absorption band in the ultraviolet-visible region for the given complexes is
- (A)\mathrm{[Co(CN)_6]^{3-} < [Co(NH_3)_6]^{3+} < [Co(NH_3)_5(H_2O)]^{3+} < [Co(NH_3)_5(Cl)]^{2+}}Correct
- (B)\mathrm{[Co(NH_3)_5(Cl)]^{2+} < [Co(NH_3)_5(H_2O)]^{3+} < [Co(NH_3)_6]^{3+} < [Co(CN)_6]^{3-}}
- (C)\mathrm{[Co(CN)_6]^{3-} < [Co(NH_3)_5(Cl)]^{2+} < [Co(NH_3)_5(H_2O)]^{3+} < [Co(NH_3)_6]^{3+}}
- (D)\mathrm{[Co(NH_3)_6]^{3+} < [Co(CN)_6]^{3-} < [Co(NH_3)_5(Cl)]^{2+} < [Co(NH_3)_5(H_2O)]^{3+}}
Answer: (A)
Solution
All four are Co(III) complexes. The absorption corresponds to , and . By the spectrochemical series CN^-NH_3H_2O$ >
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Question ID VK-037821