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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
    A radioactive substance takes 20 min to decay 25%. How much time will be taken to decay 75%                 [Orissa JEE 2005]

    A)                 96.4 min              

    B)                 68 min

    C)                 964 min               

    D)                 680 min

    Correct Answer: A

    Solution :

               For 25% decay                    \[K=\frac{2.303}{20}\log \frac{100}{75}=\frac{2.303}{20}\times 0.1249=0..1438\]                    For 75% decay,                                 \[t=\frac{2.303}{0.01438}\log \frac{100}{25}=96.4\]minute.


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