Verified Solution • 2025–26 Session moderate

QJEEM19Ch34ff: JEE Main 2019 Chemistry - Class 12 JEEM19Ch34ff Solution: Three complexes, [CoCl(NH 3 ) 5 ] 2+ (I), [Co(NH 3 ) 5 H 2 O]…

Three complexes,
[CoCl(NH3)5] 2+(I),
[Co(NH3)5H2O]3+ (II) and
[Co(NH3)6] 3+(III)
absorb light in the visible region. The correct order of the wavelength of light absorbed by them is :

Multiple Choice Options

  • A (III) > (I) > (II)
  • B (III) > (II) > (I)
  • C (I) > (II) > (III)
  • D (II) > (I) > (III)

Step-by-Step Verified Solution

As in a co-ordination compound, the strong field ligand causes higher splitting of the d-orbitals

Also we know,

strength of ligand ∝\propto 1λabsorbed{1 \over {{\lambda _{absorbed}}}}

Order of strength of ligand

NH3 > H2O > Cl-

Therefore decreasing order of wavelength absorbed is (I) > (II) > (III)

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