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CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2006

  • question_answer
    The radii of \[N{{a}^{+}}\] and \[C{{l}^{-}}\]ions are 95 pm and 181 pm respectively. The edge length of \[NaCl\] unit cell is :

    A)  276 pm                               

    B)  138 pm

    C)  552 pm                               

    D)  415 pm

    Correct Answer: C

    Solution :

    \[NaCl\] has fee structure. In fee lattice                 \[{{r}^{+}}+{{r}^{-}}=\frac{a}{2}\] where a = edge length                 \[{{r}^{+}}=95\,pm\,\,\,{{r}^{-}}=181\,pm\] Edge length \[=2{{r}^{+}}+2{{r}^{-}}\]                 \[=(2\times 95+2\times 181)\,pm\]                 = 190 + 362 = 552 pm


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