Question

There is a collection of crystalline substances in a hexagonal closed packing. If the density of matter is $2.6g/c{m}^3$, what would be the average density of matter in collection? What fraction of space is actually unoccupied?

Answer 1

In hexagonal closed packing, the packing efficiency is $74.05$%.
$\therefore$ Density of matter $=$ Packing fraction $\times$ Total density
$=\frac{74.05}{100}\times 2.6=1.93gc{m}^{-3}$
% empty space $=100-74.05=25.95$%.