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JEE Main & Advanced Chemistry Surface & Nuclear Chemistry / भूतल और नाभिकीय रसायन Question Bank Rate of decay and Half-life

  • question_answer
    \[C-14\] has a half-life of 5760 years. \[100mg\]  of a sample containing \[C-14\] is reduced to \[25mg\] in [Bihar CEE 1992; AMU 2002; MHCET 1999]

    A)                 11520 years       

    B)                 2880 years

    C)                 1440 years          

    D)                 17280 years

    Correct Answer: A

    Solution :

           \[25={{\left[ \frac{1}{2} \right]}^{n}}\times 100,{{\left[ \frac{1}{2} \right]}^{n}}=\frac{25}{100}=\frac{1}{4}={{\left[ \frac{1}{2} \right]}^{2}}\]                    n = 2, No. of half lives = 2                                 so time required = \[2\times 5760=11520\,\,yr.\]


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