• # question_answer   Among the statements (a)-(d), the incorrect ones are Octahedral Co(III) complexes with strong field ligands have very high magnetic moments When${{\Delta }_{0}}<P,$the d-electron configuration of Co(III) in an octahedral complex is $t_{eg}^{4}\,e_{g}^{2}$ Wavelength of light absorbed by $[Co{{(en)}_{3}}]{{\,}^{3+}}$is lower than that of $[Co{{F}_{6}}]{{\,}^{3-}}$ If the ${{\Delta }_{0}}$  for an octahedral complex of Co(III) is $18,000,\,c{{m}^{1}}$ the${{\Delta }_{t}}$ for its tetrahedral complex with the same ligand will be $16,000\text{ }c{{m}^{1}}$ [JEE MAIN Held on 07-01-2020 Evening] A) (c) and (d) only B) (a) and (d) only C) (a) and (b) only D) (b) and (c) only

Correct Answer: B

Solution :

[b] $C{{o}^{3+}}$with strong field complex forms low magnetic moment complex If ${{\Delta }_{0}}<P$ configuration of $~C{{o}^{3+}}$ will be $t_{g}^{6}\,e_{g}^{2}$ CFSE of ${{[Co{{(en)}_{3}}]}^{3+}}$is more than ${{[Co{{F}_{6}}]}^{3-}}$ $\Rightarrow \,\,{{\lambda }_{absorbed}}$ of ${{[Co{{(en)}_{3}}]}^{3+}}$ is less than ${{[Co{{F}_{6}}]}^{3-}}$ ${{\Delta }_{t}}=\frac{4}{9}\,{{\Delta }_{0}}=\frac{4}{9}\,\times 18000=18000\,c{{m}^{-\,1}}$ Hence, and are incorrect

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