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12th Class Chemistry Nuclear Chemistry / नाभिकीय रसायन Question Bank Critical Thinking Nuclear chemistry

  • question_answer
    What is the half-life of a radioactive substance if 87.5% of any given amount of the substance disintegrates in 40 minutes                   [Kerala CET 1996]

    A)            160 min                                  

    B)            10 min

    C)            20 min                                     

    D)            13 min 20 sec

    Correct Answer: D

    Solution :

           \[K=\frac{2.303}{40}\log \frac{a}{a-0.875a}=\frac{2.303}{40}\log 8\]                    \[=0.05199{{\min }^{-1}}\] \[{{t}_{1/2}}\] = 0.693/0.05199                    = 13.33 min. = 13 min 20 sec.


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