RAJASTHAN PMT Rajasthan - PMT Solved Paper-2005

  • question_answer
    \[_{90}T{{h}^{232}}{{\xrightarrow{{}}}_{82}}P{{b}^{208}}\] The number of \[\alpha \] and \[\beta \] particles emitted during the above reaction is:

    A) \[8\alpha \]and\[4\beta \]                          

    B)  \[8\alpha \]and\[16\beta \]

    C) \[4\alpha \]and\[2\beta \]   

    D)        \[6\alpha \]and\[4\beta \]

    Correct Answer: D

    Solution :

    \[_{90}T{{h}^{232}}{{\xrightarrow{{}}}_{82}}P{{b}^{208}}\] In the above disintegration. Change in atomic weight \[=232-208=24\]. We know that for the emission of one \[\alpha -\]particle the atomic weight is decreased by 4. \[\therefore \]number of a-particles emitted                 \[=\frac{24}{4}=6\] After the emission of \[6\,\,\alpha -\]particles, the change in atomic number\[=90-12=78\]\[(\because \,\,\alpha {{=}_{2}}H{{e}^{4}})\]. The increase in atomic number from \[78\] to\[82=4\] \[\therefore \]number of \[\beta -\]particles emitted\[=4\]                 \[(\because \,\,\beta =-e{}^\circ )\] Hence, \[6\,\,\,\alpha -\]particles and \[4\,\,\beta -\]particles are emitted.


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