BCECE Medical BCECE Medical Solved Papers-2011

  • question_answer
    Given mass number of gold =197, Density of gold = 19.7 \[g/c{{m}^{3}}\] Avogadros number \[=6\times {{10}^{23}}\]. The radius of the gold atom is approximately

    A)  \[1.5\times {{10}^{-8}}m\]

    B)  \[1.7\times {{10}^{-9}}m\]

    C)  \[1.5\times {{10}^{-10}}m\]   

    D)  \[1.5\times {{10}^{-12}}m\]

    Correct Answer: C

    Solution :

    Volume occupied by one gram atom of gold                 \[=\frac{197\,\,g}{19.7\,g/{{m}^{3}}}=10\,c{{m}^{3}}\] Volume of one atom \[=\frac{10}{6\times {{10}^{-23}}}\]                 \[=\frac{5}{3}\times {{10}^{23}}c{{m}^{3}}\] Let r be the radius of the atom \[\therefore \] \[\frac{4}{3}\pi {{r}^{3}}=\frac{5}{3}\times {{10}^{23}}\]                 \[{{r}^{3}}=\frac{50\times {{10}^{-24}}}{4\times 3.14}\] \[r=1.5\times {{10}^{-10}}m\]


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