Question

Aluminium forms face centered cubic crystals .The density of $AI$ is $2.7g/c{m}^3$ .Calculate the length of the side of the unit cell $AI$. (At.wt. of $AI=27$)

Answer 1

For FCC, number of unit cells= $4$

Density= $2.7g/c{m}^3$

$d=\frac{Z\times M}{a^3\times N_A}$

$\Rightarrow 2.7=\frac{4\times 27}{a^3\times 6.023\times {10}^{23}}$

$\Rightarrow a^3=\frac{4\times 27}{2.7\times 6.023\times {10}^{23}}$

$\Rightarrow a=4.05\times {10}^{-8}cm$