CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2011

  • question_answer
    Substance which is weakly repelled by a magnetic field is

    A)  \[{{O}_{2}}\]    

    B)         \[{{H}_{2}}O\]

    C)  \[Cr{{O}_{2}}\]                

    D)         \[F{{e}_{3}}{{O}_{4}}\]

    E)  \[ZnF{{e}_{2}}{{O}_{4}}\]

    Correct Answer: B

    Solution :

    \[{{O}_{2}}\]molecule is paramagnetic and the presence of two unpaired electrons in the\[\overset{*}{\mathop{\pi }}\,(2{{p}_{x}})\]or\[\overset{*}{\mathop{\pi }}\,(2{{p}_{y}})\]molecular orbitals accounts for its paramagnetic nature. Similary in \[Cr{{O}_{2}},\] \[F{{e}_{3}}{{O}_{4}}\]and\[ZnF{{e}_{2}}{{O}_{4}},\]the d-orbitals of transition elements are not fulfilled and have unpaired electrons and hence, are paramagnetic. Whereas,\[{{H}_{2}}O\]is diamagnetic because of the presence of all paired electrons and hence repelled by magnetic field.


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