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NEET NEET SOLVED PAPER 2016 Phase-I

  • question_answer
    Lithium has a bcc structure. Its density is \[530\,\text{kg}\,{{\text{m}}^{-3}}\] and its atomic mass is \[6.94\text{ g mo}{{\text{l}}^{1~}}\]Calculate the edge length of a unit cell of Lithium metal.                                                                                                   \[({{N}_{A}}=\text{ }6.02\text{ }\times \text{ }{{10}^{23}}\text{ mo}{{\text{l}}^{1}})\]

    A)  154 pm                               

    B)   352 pm

    C)   527 pm                              

    D)   264 pm

    Correct Answer: B

    Solution :

                     \[\rho =\frac{Z\times M}{{{N}_{A}}\times {{a}^{3}}}\] For bcc structure \[Z=2,\,\,\rho =530\,kg\,{{m}^{-3}}=0.530\,g\,c{{m}^{-3}}\] \[0.530=\frac{2\times 6.94}{6.02\times {{10}^{23}}\times {{a}^{3}}}\] \[{{a}^{3}}=4.348\times {{10}^{-23}}\,c{{m}^{3}}\] \[a=3.52\times {{10}^{-8}}\,cm\] \[a=352\,pm\]


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