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Question

Chemistry Question on coordination compounds

Which of the following coordination entities should be expected to absorb light of lowest frequency?

A

[Cr(en)3]3+[Cr(en)_3]^{3+}

B

[CrCl6]3[CrCl_6]^{3-}

C

[Cr(NH3)6]3+[Cr(NH_3)_6]^{3+}

D

[Cr(CN)6]3[Cr(CN)_6]^{3-}

Answer

[CrCl6]3[CrCl_6]^{3-}

Explanation

Solution

The coordination entity, for which crystal fieid spiitting is smaller, absorbs light of Io west frequency. Weaker the ligand fieid strength, smaller will be the crystal fieid splitting. The order of field strength of various ligands is as CN>en>NH3>Cl\, \, \, \, \, \, \, \, \, \, \, \, \, \, CN > en > NH_3 > Cl Hence, [CrCl6]3[CrCl_6 ]^{3-} due to the presence of ClCl^- ligand absorbs light of Iowest frequency.