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NEET Sample Paper NEET Sample Test Paper-66

  • question_answer
    Atomic weight of boron is 10.81 and it has two isotopes \[_{5}{{B}^{10}}\] and\[_{5}{{B}^{11}}\]. Then ratio of \[_{5}{{B}^{10}}:\,{{\,}_{5}}{{B}^{11}}\] in nature would be

    A) \[19:81\]           

    B) \[10: 11\]

    C) \[15 : 16\]                     

    D) \[81 : 19\]

    Correct Answer: A

    Solution :

    Let the percentage of \[{{B}^{10}}\] atoms be x, then Average atomic weight \[=\,\,\frac{10x+11(100-x)}{100}\,\,=\,\,10.81\] \[\Rightarrow \,\,x=19\,\,\,\,\,\,\therefore \,\,\frac{{{N}_{{{B}^{10}}}}}{{{N}_{{{B}^{11}}}}}\,\,=\,\,\frac{19}{81}\]


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