NEET Sample Paper NEET Sample Test Paper-80

  • question_answer
    A metal M \[\left( Z = 40 \right)\] depending on temperature crystallises in FCC and BCC crystal structure whose unit length areas are 3.5 and \[3\overset{{}^\circ }{\mathop{A}}\,\] respectively. The ratio of its density in FCC and BCC is

    A)  1.259              

    B)  2

    C)  \[\frac{8}{\sqrt{6}}\]                            

    D)  \[\frac{16}{3\sqrt{6}}\]

    Correct Answer: A

    Solution :

    For FCC \[\operatorname{density} = {{d}_{1}}\], \[=\,\,\,\frac{4\times {{z}_{1}}}{{{N}_{A}}\times a_{1}^{3}}\] For BCC \[density={{d}_{2}}\] \[=\,\,\,\frac{2\times {{z}_{1}}}{{{N}_{A}}\times a_{2}^{3}}\] \[\frac{{{d}_{1}}}{{{d}_{2}}}=\frac{4}{2}\times \frac{a_{2}^{3}}{a_{1}^{3}}\,\,=\,\,\frac{{{(3\times {{10}^{-\,8}})}^{3}}}{{{(3.5\times {{10}^{-8}})}^{3}}}\] \[=\,\,\,1.259\]


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