J & K CET Engineering J and K - CET Engineering Solved Paper-2009

  • question_answer
    In the radioactive, decay, \[_{y}{{X}^{z}}\xrightarrow{(-8\alpha \,\text{and}\,\text{6}\beta )}{{\,}_{82}}P{{b}^{206}},x,y\]and \[z\]are

    A)  U, 92 and 235

    B)  Th, 90 and 232

    C)  Pu, 94 and 238

    D)  U, 92 and 238

    Correct Answer: D

    Solution :

     The given radioactive decay can be written in the following manner: \[_{y}{{X}^{z}}\xrightarrow{{}}{{\,}_{82}}P{{b}^{206}}+{{8}_{2}}H{{e}^{4}}+{{6}_{-1}}{{\beta }^{o}}\] On comparing, \[Z=206+8\times 4+6\times 0\] \[Z=238\] \[y=82+8\times 2-1\times 6\] \[=82+16-6=92\] Atomic number of uranium (U) is 92, so X is U.


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