1. Tardigrade
  2. Question
  3. Chemistry
  4. 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 :

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Q. Three complexes,
$[CoCl(NH_3)_5]^{2+} (I) $ ,
$[Co(NH_3)_5H_2O]^{3+} (II)$ and
$ [Co(NH_3)_6]^{3+} (III)$
absorb light in the visible region. The correct order of the wavelength of light absorbed by them is :

JEE MainJEE Main 2019Coordination Compounds

Solution:

A complex having strong field ligand has tendency to absorb light of highest energy. Among the three complexes.
$[Co(NH_3 )_6]^{+3}$ will absorb radiation of highest energy and least wavelength.
$[ Co(NH_3)_5 H_2 O ]^{3+}$ has field weaker than the above compound and therefore absorb radiation of lesser energy and more wavelength.
$[ CoCl(NH_3)_5]^{2+}$ has the weakest field and therefore will absorb light of least energy and highest wavelength.
Strength of ligand $NH_3 > H_2O > Cl$.