RAJASTHAN PMT Rajasthan - PMT Solved Paper-2001

  • question_answer
    The half-life of 1 molecule is 1 hour, its rate of dissociation is 1000 per second at that time then after 3 hours. Its rate of dissociation will be:

    A)  \[333\]                                

    B)  \[100\]

    C)  \[250\]                

    D)         \[125\]

    Correct Answer: A

    Solution :

    Rate of dissociation \[\frac{d[N]}{dt}=\lambda {{N}_{1}}=1000\] \[{{N}_{1}}\] atom \[t/2\] = present in 1 hour \[{{N}_{2}}\] atom t = present in 3 hour                 \[\lambda =\frac{2.303}{t/2}\log \frac{{{N}_{0}}}{{{N}_{1}}}\]                 \[\lambda =\frac{2.303}{t}\log \frac{{{N}_{0}}}{{{N}_{2}}}\] \[\frac{2.303}{1}\log \frac{{{N}_{0}}}{{{N}_{1}}}=\frac{2.303}{3}\log \frac{{{N}_{0}}}{{{N}_{2}}}\]                 \[\frac{{{N}_{1}}}{{{N}_{2}}}=\frac{3}{1}\] or  \[\frac{\lambda {{N}_{1}}}{\lambda {{N}_{2}}}=\frac{3}{1}\]                 \[\lambda {{N}_{1}}=3\lambda {{N}_{2}}\] or            \[1000\,per\,\sec =3\lambda {{N}_{2}}\]                 \[\lambda {{N}_{2}}=\frac{1000}{3}=333\sec \]


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