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# X-ray diffraction studies show that copper crystallizes in an fcc unit cell with cell edge of $3.608\times 10^{-8}$cm.In a separate environment,copper is determined to have a density of $8.92g/cm^3$,calculate the atomic (molar) mass of the copper.

$\begin{array}{1 1}63.1u\\73.1u\\53.1u\\43.1u\end{array}$

In case of fcc lattice,number of atoms per unit cell,$x=4$ atoms
Therefore,$M=\large\frac{dN_A a^3}{z}$
$\Rightarrow \large\frac{8.92\times 6.023\times 10^{23}\times (3.608\times 10^{-8})^3}{4}$g/mol
$\Rightarrow$ 63.1g/mol
$\therefore$ Atomic mass of copper =63.1u