KVPY Sample Paper KVPY Stream-SX Model Paper-29

  • question_answer
    Pottasium has a bcc structure with nearest neighbour distance \[4.52\overset{\text{o}}{\mathop{\,\text{A}}}\,\]. Its atomic weight is 39. Its density (in kg \[{{m}^{-3}}\]) will be

    A) 454

    B) 804

    C) 852      

    D) 910

    Correct Answer: D

    Solution :

    For \[bcc,\]
    \[d=\frac{\sqrt{3}}{2}a\,\text{or}\,a=\frac{2d}{\sqrt{3}}=\frac{2\times 4.52}{1.732}=5.219\overset{\text{o}}{\mathop{\text{A}}}\,=522pm\]\[\rho =\frac{\operatorname{Z}\times M}{{{\operatorname{a}}^{3}}\times {{\operatorname{N}}_{A}}\times {{10}^{-30}}}\]\[=\frac{2\times 39}{{{\left( 522 \right)}^{3}}\times \left( 6.023\times {{10}^{23}} \right)\times {{10}^{-30}}}\]

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