The wavelength of light absorbed for the following complexes are in the order ( (I) [Co(NH _ 3 )_6]^ 3+ ; (II) [Co(H _ 2 O)_ 6]^ 3+ ; (III) [Co(CN)_ 6]^ 3- ; (IV) [Co(NH _ 3 )_5(H _ 2 O)]^ 3+ ; (V) [CoF _ 6 ]^ 3- )

Correct answer: B. III II > IV > I > III

JEE Main 202624 JanuaryEvening Shift

JEE Main 2026 · 24 January · Evening Shift · Chemistry · Coordination Compounds

The wavelength of light absorbed for the following complexes are in...

The wavelength of light absorbed for the following complexes are in the order (\underset{\text{(I)}

}{\left[\mathrm{Co}\left(\mathrm{NH}}_{3}\right)_6\right]^{3+}} ;\underset{\text{(II)}}{\left[\mathrm{Co}\left(\mathrm{H}

}_{2}

\mathrm{O}\right)_

6\right]^{3+}} ;\underset{\text{(III)}

}{\left[\mathrm{Co}(\mathrm{CN})_

6\right]^{3-}} ;\underset{\text{(IV)}

}{\left[\mathrm{Co}\left(\mathrm{NH}}_{3}\right)_5\left(\mathrm{H}

}_{2}

\mathrm{O}\right)\right]^{3+}

} ;\underset{\text{(V)}}{\left[\mathrm{CoF}}_{6}\right]^{3-}})

B. III $<$ I $<$ IV $<$ II $<$ V

Wavelength of light absorbed increases as C.F.S.E of complex decreases.

[Co(CN)_6]^{3-}

has maximum CFSE

[CoF_6]^{3-}

has least CFSE
Ligand field strength

\uparrow

; C.F.S.E

\uparrow

Correct wavelength order.

V > II > IV > I > III