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Coordination Compounds

Question
CBSEENCH12011431

Correct increasing order for the wavelengths of absorption in the visible region for the complexes of Co3+ is

  • [Co(en)3]3+, [Co(NH3)6]3+, [Co(H2O)6]3+

  • [Co(H2O)6]3+, [Co(en)3]3+, [Co(NH3)6]3+

  • [Co(H2O)6]3+, [Co(NH3)6]3+, [Co(en)3]3+

  • [Co(NH3)6]3+, [Co(en)3]3+, [Co(H2O)6]3+

Solution

A.

[Co(en)3]3+, [Co(NH3)6]3+, [Co(H2O)6]3+

The order of the ligand in the spectrochemical series
H2O < NH3< en
Hence, the wavelength of the light observed will be in the order
[Co(H2O)6]3+, [Co(NH3)6]3+, [Co(en)3]3+
Thus, wavelength absorbed will be in the opposite order
[Co(en)3]3+, [Co(NH3)6]3+, [Co(H2O)6]3+