NEET Chemistry NEET PYQ-Oxygen Family

  • question_answer
    Which one of the following compounds is a peroxide?                          [AIPMT (S) 2010]

    A) KO2

    B) BaO2

    C) MnO2

    D) NO2

    Correct Answer: B

    Solution :

    [b] Key Idea In peroxides, the oxidation state of O is 1 and they give \[{{H}_{2}}{{O}_{2}},\]with dilute acids, and have peroxide linkage.
    In \[K{{O}_{2}}\],                     \[+1+(x\times 2)=0\]
    \[x=-\frac{1}{2}\](thus, it is a superoxide, not a peroxide.)
    In \[Ba{{O}_{2}},\]                         \[+2+(x\times 2)=0\]
                                        \[x=-1\]
    Thus, it is a peroxide. Only it gives \[{{H}_{2}}{{O}_{2}}\] when reacts with dilute acids and has peroxide linkage as\[\underset{peroxide\,linkage}{\mathop{B{{a}^{2+}}{{[O-O]}^{2-}}}}\,\]
    In \[\text{Mn}{{\text{O}}_{\text{2}}}\] and \[\text{N}{{\text{O}}_{\text{2}}},\]Mn and N exhibit variable oxidation states, thus, the oxidation state of O in these is - 2. Hence, these are not peroxides.
    Thus, it is clear, that among the given molecules only \[\text{Ba}{{\text{O}}_{\text{2}}}\] is a peroxide.


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