BCECE Medical BCECE Medical Solved Papers-2008

  • question_answer
    If two molecules of A and B having mass 100 kg and 64 kg and rate of diffusion of A is \[12\times {{10}^{-3}}\], then what will be the rate of diffusion of B?

    A)  \[15\times {{10}^{-3}}\]     

    B)  \[64\times {{10}^{-3}}\]

    C)  \[5\times {{10}^{-3}}\]

    D)  \[46\times {{10}^{-3}}\]

    Correct Answer: A

    Solution :

    Key Idea According to Grahams law of diffusion At constant pressure and temperature the rate of diffusion of a gas is inversely proportional to the square root of its vapour density,                 Rate of diffusion (r) \[\propto \frac{1}{\sqrt{d}}\] Molecular weight (M) = 2 \[\times \]vapour density                 \[\frac{{{r}_{1}}}{{{r}_{2}}}=\sqrt{\frac{{{M}_{2}}}{{{M}_{1}}}}\]                 \[{{m}_{A}}=\left( \frac{100}{2} \right)\] kg/molecule                 \[{{m}_{B}}=\left( \frac{64}{2} \right)\] kg/molecule                 \[{{r}_{A}}=12\times {{10}^{-3}}\]and \[{{r}_{B}}=?\]                 \[\frac{{{r}_{A}}}{{{r}_{B}}}=\sqrt{\frac{{{d}_{B}}}{{{d}_{A}}}}=\sqrt{\frac{{{M}_{B}}}{{{M}_{A}}}}\] \[\frac{12\times {{10}^{-3}}}{{{r}_{B}}}=\sqrt{\frac{64/2}{100/2}}=\sqrt{\frac{64}{100}}=\frac{8}{10}\]                 \[{{r}_{B}}=\frac{12\times {{10}^{-3}}\times 10}{8}\] \[=15\times {{10}^{-3}}\]


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