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RAJASTHAN ­ PET Rajasthan PET Solved Paper-2005

  • question_answer
    The atomic weight of boran is 10.81 and it has two isotopes \[_{5}{{\beta }^{10}}\] and \[_{5}{{\beta }^{11}}\]. Then ratio of \[_{5}{{\beta }^{10}}\]: \[_{5}{{\beta }^{11}}\] in nature would be

    A)  19 : 81            

    B)  10 : 11

    C)  15 : 61           

    D)  81 : 19

    Correct Answer: A

    Solution :

     Let percentage of\[{{B}^{10}}\]atom is\[x,\]then average atomic weight \[=\frac{10x+11(100-x)}{100}\] \[=10.81\] \[x=19\] \[\therefore \] \[\frac{_{5}{{B}^{10}}}{_{5}{{B}^{11}}}=\frac{19}{81}\]


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