If the unit cell edge length of an FCC crystal ( Molecular mass = $58.5\frac{g}{mol}$) is 500 pm. If the density of unit cell is x, find the value of 100x.

Given 

Length is 600 pm

Density (d) = $\frac{Z.M}{N_A{a}^3}$

M=23+35.5=58.5g

Z=4

$N_A$= Average number =$6.023\times {10}^{23}$

$a=600 pm=600\times {10}^{-10}$

Density = $\frac{4\times 58.5}{6.023\times {10}^{23}\times {\left(600\times {10}^{-10}\right)}^3}=1.79\frac{g}{c{m}^3}$