JEE Main & Advanced Sample Paper JEE Main Sample Paper-20

  • question_answer
    A sample of \[{{U}^{238}}({{t}_{1/2}}=4.5\times {{10}^{9}}\,yrs)\] is found to contain \[11.9\,gm\,{{U}^{238}}\] and \[20.6\,gm\,P{{b}^{206}}.\]The age of sample is (Given In \[2=0.693,\,\]In \[3=1.1\]]

    A)  \[1.64\times {{10}^{-10}}yrs\]  

    B)  \[7.14\times {{10}^{9}}yrs\]

    C)  \[2.25\times {{10}^{9}}yrs\]   

    D)  None of these

    Correct Answer: B

    Solution :

     \[t=\frac{1}{\lambda }\] In \[\frac{{{n}_{U}}+{{n}_{Pb}}}{{{n}_{U}}};{{n}_{U}}=\]no. of mole of \[{{U}^{238}}\] \[t=\frac{1}{\lambda }\] In \[\left( \frac{0.15}{0.05} \right);\] \[{{n}_{Pb}}=\]no-of mole of \[P{{b}^{206}}\] \[t=\frac{1}{\lambda }\] In \[(3)=\frac{1.1}{0.693}\times 4.5\times {{10}^{9}}=7.14\times {{10}^{9}}\]years


You need to login to perform this action.
You will be redirected in 3 sec spinner