KVPY Sample Paper KVPY Stream-SX Model Paper-15

  • question_answer
    Among the following metal carbonyls, the C ? 0 bond order is lowest in

    A) \[{{[Mn{{(CO)}_{6}}]}^{+}}\]

    B) \[[Fe{{(CO)}_{5}}]\]

    C) \[[Cr{{(CO)}_{6}}]\]

    D) \[{{[V\,{{(CO)}_{6}}]}^{-}}\]

    Correct Answer: B

    Solution :

    Greater the extent of \[d\pi -p\pi \] back bonding, smaller will be the bond order of \[CO\] bond in metal carbonyls. More are the number of valence shell electrons (d - electrons), maximum is the chance of \[p\pi -d\pi \] back bonding and thus lowest will be the bond order of \[CO\] bond.
    The number of d-etectrons of metal in given complexes are as follows:
    [a] \[{{[Mn{{(CO)}_{6}}]}^{+}}\]
    \[Mn\]is present as \[M{{n}^{+}},\] thus the electronic configuration is \[3{{d}^{5}}4{{s}^{1}}.\]
    [b] \[[Fe{{(CO)}_{5}}]\]
    Fe is present in zero oxidation state, thus the electronic configuration will be \[3{{d}^{6}}4{{s}^{0}}.\]
    [c] \[[Cr{{(CO)}_{6}}]\]
    \[Cr\]is present in zero oxidation state, thus the electronic configuration is \[3{{d}^{5}}4{{s}^{1}}.\]
    [d] \[{{[V{{(CO)}_{6}}]}^{-}}\]
    V is present as \[{{V}^{+}}\] in given complex.
    Thus, the electronic configuration is \[3{{d}^{3}}4{{s}^{1}}.\]
    Thus, \[[Fe{{(CO)}_{5}}]\]has lowest bond order of \[CO\]bond.


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