JEE Main & Advanced JEE Main Paper Phase-I (Held on 07-1-2020 Evening)

  • 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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