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A metal crystallizes into two cubic system-face centred cubic (fcc) and body centred cubic (bcc) whose unit cell lengths are 3.5 and 3.0Å respectively. Calculate the ratio of densities of fcc and bcc. |
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Answer» We know that d =\(\frac{zM}{N_aa^3}\) For fcc, z=4 therefore d =\(\frac{4\times M}{Na(3.5\times10^{-8})^3\,g/cm^3}\) For bcc, z=2 therefore d’ = \(\frac{2\times M}{Na(3.0\times10^{-8})^3\,g/cm^3}\) \(\frac{d}{d'}\) = \(\frac{\frac{4}{(3.5\times10^{-8})^3}}{\frac{2}{(3.0\times10^{-8})^3}}\) = 1.26:1 |
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