NEET Sample Paper NEET Sample Test Paper-60

  • question_answer
    The number of atoms in 100g of a fee crystal with density = 10.0g/cm3 and cell edge equal to 200pm is equal to:

    A) \[5\times {{10}^{24}}\]           

    B) \[5\times {{10}^{25}}\]

    C) \[6\times {{10}^{23}}\]           

    D) \[2\times {{10}^{25}}\]

    Correct Answer: A

    Solution :

    [a] \[~5\times {{10}^{24}}\] \[P=\frac{z\times M}{{{a}^{3}}\times {{10}^{-3}}\times NO}\] \[or\,M=\frac{10\times {{(200)}^{3}}\times {{10}^{-30}}\times 6\times {{10}^{23}}}{4}=12\] Thus, 12g contain \[=\text{ }No=6\times {{10}^{23}}\]atom \[\therefore \,100g\,will\,contain\,=\frac{6\times {{10}^{23}}}{12}\times 100\]                         \[=5\times {{10}^{24}}\]


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