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JEE Main & Advanced Chemistry The Solid State / ठोस प्रावस्था Question Bank Crystallography and Lattice

  • question_answer
    How many molecules are there in the unit cell of sodium chloride             [MP PMT 1996; MP PET 1997]

    A)                 2             

    B)                 4

    C)                 6             

    D)                 8

    Correct Answer: B

    Solution :

                    In \[NaCl\] (rock salt) : Number of \[N{{a}^{+}}\]ions \[=12\] (at edge centers) \[\times \frac{1}{4}+1\](at body centre)\[\times 1=4\]. Number of \[C{{l}^{-}}\]ions \[=8\] (at corners)\[\times \frac{1}{8}+6\] (at face centre) \[\times \frac{1}{2}=4\]. Thus 4 formula units per unit cell.


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