Haryana PMT Haryana PMT Solved Paper-2002

  • question_answer
    The half-life of radium is 1620 year and its            atomic weight is 226 gm/mole. The number of   atoms that will decay from its 1g sample per   second is :

    A)  \[3.61\times {{10}^{10}}\]                          

    B) \[3.6\times {{10}^{12}}\]

    C)  \[3.1\times {{10}^{15}}\]            

    D)  \[31.1\times {{10}^{15}}\]

    Correct Answer: A

    Solution :

                    Rate of disintegration \[\frac{dN}{dt}=\lambda N\] From Avagadros principle Number of atoms in 1 gram radium                 \[=\frac{6\times {{10}^{23}}}{226}\] decay constant \[\lambda =\frac{1}{\tau }\]                                 \[=\frac{0.093}{1620}years\]                                 \[=\frac{0.693}{1620\times 365\times 24\times 60\times 60}\]                                 \[=\frac{0.693}{1620\times 3.15\times {{10}^{7}}}{{\sec }^{-1}}\] \[\therefore \]  \[\frac{dN}{dt}=\frac{0.693}{1620\times 3.15\times {{10}^{7}}}\times \frac{6\times {{10}^{23}}}{226}\]                 \[=3.61\times {{10}^{10}}per\,\sec .\]


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