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

  • question_answer
    A first order nuclear reaction is half completed in 45 minutes. How long does it need 99.9% of the reaction to be completed                    [KCET 2001]

    A)            5 hours                                   

    B)            7.5 hours

    C)            10 hours                                 

    D)            20 hours

    Correct Answer: B

    Solution :

           \[k=\frac{0.693}{0.75\text{hr}}=\frac{\text{2}\text{.303}}{\text{t}}\log \frac{a}{a-0.999a}\]                    \[=\frac{2.303}{t}\log {{10}^{3}}=7.5\,hrs\].       


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