JEE Main & Advanced Chemistry The Solid State / ठोस प्रावस्था Sample Paper Topic Test - Solid State

  • question_answer
    A metallic element has a cubic lattice. Each edge of the unit cell is \[2{{A}^{0}}\]. The density of the metal is \[2\text{ }g\text{ }c{{m}^{-3}}\]. The unit cells in 200 g of the metal are

    A) \[1\times {{10}^{25}}\]

    B) \[1\times {{10}^{24}}\]

    C) \[1\times {{10}^{22}}\]

    D) \[1\times {{10}^{20}}\]

    Correct Answer: A

    Solution :

    [a] Edge length of the unit cell
    \[=2{{A}^{0}}=2\times {{10}^{-8}}cm\]
    Volume of the unit cell \[={{(2\times {{10}^{-8}})}^{3}}c{{m}^{3}}\]
    \[=8\times {{10}^{-24}}c{{m}^{3}}\]
    Mass of unit cell\[\text{= volume  }\!\!\times\!\!\text{  density}\]
    \[=8\times {{10}^{-24}}\times 2.5g\]
    No. of unit cells in 200 g of the metal
    \[\frac{\text{mass of metal}}{\text{mass of unitcell}}=\frac{200}{8\times {{10}^{-24}}\times 2.5}=1\times {{10}^{25}}\]


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