CMC Medical CMC-Medical Ludhiana Solved Paper-2010

  • question_answer
    The half-life of radium is 1620 yr and its atomic weight is 226 g/mol. The number of atoms that will decay from its 1 g 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 Avogadros principle Number of atoms in 1 g radium \[=\frac{6\times {{10}^{23}}}{226}\] Decay constant\[\lambda =\frac{1}{\tau }\] \[=\frac{0.693}{1620}yr\] \[=\frac{0.693}{1620\times 365\times 24\times 60\times 60}\] \[=\frac{0.693}{1620\times 3.15\times {{10}^{7}}}{{s}^{-1}}\] \[\therefore \]\[\frac{dN}{dt}=\frac{0.693}{1620\times 3.15\times {{10}^{7}}}\times \frac{6\times {{10}^{23}}}{226}\] \[=3.61\times {{10}^{10}}\,\text{per}\,\,\text{sec}\]


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