JEE Main & Advanced JEE Main Paper (Held On 11-Jan-2019 Morning)

  • question_answer
    A solid having density of \[9\times {{10}^{3}}kg\,{{m}^{-3}}\]forms face centred cubic crystals of edge length \[200\sqrt{2}pm.\] What is the molar mass of the solid? [Avogadro constant \[\cong 6\times {{10}^{23}}mo{{l}^{-1}},\]\[\cong \pi 3\]] [JEE Main Online Paper (Held On 11-Jan-2019 Morning]

    A) \[0.0432\text{ }kg\text{ }mo{{l}^{-1}}\]                       

    B) \[0.016\text{ }kg\text{ }mo{{l}^{-1}}\]

    C) \[0.4320\text{ }kg\text{ }mo{{l}^{-1}}\]  

    D)               \[0.0305\text{ }kg\text{ }mo{{l}^{-1}}\]

    Correct Answer: D

    Solution :

    \[\rho =\frac{Z\times M}{{{a}^{3}}\times {{N}_{A}}}\] \[9\times {{10}^{3}}=\frac{4\times M}{{{(200\sqrt{2}\times {{10}^{-12}})}^{3}}\times 6\times {{10}^{23}}}\] \[M=\frac{9\times {{10}^{3}}\times 16\times \sqrt{2}\times 6\times {{10}^{-7}}}{4}\]\[=0.0305kg/mol\]


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