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JCECE Engineering JCECE Engineering Solved Paper-2006

  • question_answer
    Half-life of a substance is\[6\min \]. If its initial amount is\[32\,\,g\], then amount present after \[18\,\,\min \] is:

    A) \[4\,\,g\]                                            

    B) \[8\,\,g\]

    C) \[16\,\,g\]                                          

    D)  \[2\,\,g\]

    Correct Answer: A

    Solution :

    \[{{t}_{1/2}}=6\min \]                 \[{{N}_{0}}=32\,\,g\] Total time\[=18\min \]                 \[\frac{N}{{{N}_{0}}}{{\left( \frac{1}{2} \right)}^{n}}\]                 \[n=\frac{Total\,\,time}{Half-life}=\frac{18}{6}=3\]                 \[\frac{N}{32}={{\left( \frac{1}{2} \right)}^{3}}\]                 \[\frac{N}{32}=\frac{1}{8}\]                 \[N=\frac{32}{8}=4\,\,g\]


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