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CMC Medical CMC-Medical VELLORE Solved Paper-2013

  • question_answer
    Photochemical dissociation produces a normal oxygen atom and a oxygen atom 2.5 eV more energetic than normal one. Also the average bond energy of \[{{O}_{2}}\] into normal oxygen is 498 kJ\[mo{{l}^{-1}}\]. Determine the longest    wavelength required for photochemical decomposition of\[{{O}_{2}}\].

    A)  126 nm               

    B)  175 nm

    C)  190 nm               

    D)  205 nm

    Correct Answer: A

    Solution :

                    BE of \[{{O}_{2}}\] per molecule\[=\frac{498\times {{10}^{3}}}{6.023\times {{10}^{23}}}J\] \[=826\times {{10}^{-19}}J\] Energy required for photochemical decom-position of one molecule of \[{{O}_{2}}=826\times {{10}^{-19}}J+2.5\times 1.6\times {{10}^{-19}}J\]\[=1.22\times {{10}^{-18}}J\] \[\lambda =\frac{hc}{E}=\frac{6.625\times {{10}^{-34}}\times 3\times {{10}^{8}}}{1.22\times {{10}^{-18}}}=126\,nm\]


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