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

  • question_answer
    A radioactive element with half-life 6.5 hrs has \[48\times {{10}^{19}}\]atoms. Number of atoms left after 26 hrs [BHU 2003]

    A)            \[24\times {{10}^{19}}\]  

    B)            \[12\times {{10}^{19}}\]

    C)            \[3\times {{10}^{19}}\]    

    D)            \[6\times {{10}^{19}}\]

    Correct Answer: C

    Solution :

           \[{{N}_{t}}={{N}_{o}}{{\left( \frac{1}{2} \right)}^{n}}\]\[=48\times {{10}^{19}}{{\left( \frac{1}{2} \right)}^{26/6.5}}\]                    \[=48\times {{10}^{19}}{{\left( \frac{1}{2} \right)}^{4}}=3\times {{10}^{19}}\].


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