Question

A compound forms cubic close packed structure. What is the total number of voids in $1.2mol$ of it?

Answer 1

In CCP, number of CCP forming atoms per unit cell = 4
$\therefore N=4$
$\text{Number of octahedral voids}=N=4$
$\text{Numer of tetrahedral voids}=2N=2\times 4=8$
$\therefore$ $\text{Total number of voids per unit cell}=12$
$\text{Total number of voids per CCP forming atom}=\frac{12}{4}=3$
$\because$ In $1mol$ of compound, the total no. of voids $=3\times Avagadronumber=(3\times 6.023\times {10}^{23})$
$\therefore$ In $1.2mol$ compound,
$\text{Total no. of voids}=3\times 1.2\times 6.023\times {10}^{23}=21.68\times {10}^{23}$