Manipal Medical Manipal Medical Solved Paper-2014

  • question_answer
    Pyrite, \[Fe{{S}_{2}}\] crystallises in a cubic unit cell with a cell edge of 0.540 nm. The density of pyrite is 5.02\[g/c{{m}^{2}}\]. How many \[F{{e}^{2+}}\]and \[S_{2}^{2-}\] ions are present in a single unit cell? \[(S=32,Fe=56u)\]

    A) \[1F{{e}^{2+}}\] and \[1S_{2}^{2-}\]

    B) \[2F{{e}^{2+}}\]and \[2S_{2}^{2-}\]

    C)  \[4F{{e}^{2+}}\]and \[4S_{2}^{2-}\]

    D) \[6F{{e}^{2+}}\]and \[6S_{2}^{2-}\]

    Correct Answer: C

    Solution :

    \[d=\frac{ZM}{{{a}^{3}}{{N}_{A}}}\] \[5.02=\frac{Z\times 120}{6.023\times {{10}^{23}}\times {{(5.4\times {{10}^{-8}})}^{3}}}\] Z = 4 i.e., \[4F{{e}^{2+}}\] and \[4S_{2}^{2-}\] ions are present in a single unit cell.


You need to login to perform this action.
You will be redirected in 3 sec spinner