Question

$Ga$ (atomic mass $70u$ ) crystallizes in a hexagonal close packed structure. The total number of voids in $0.581g$ of $Ga$ is _______.$\times 10^{21}.$ (Round off to the Nearest Integer).

Answer 1

Answer: 15

$HCP$ structure : Per atom, there will be one octahedral void $(OV)$ and two tetrahedral voids $(TV)$.

Therefore total three voids per atom are present in $HCP$ structure.

$\to$ therefore total no of atoms of $Ga$ will be-

$=\frac{\text{ Mass }}{\text{ Molar Mass }}\times N_A=\frac{0.581g}{70g/mol}\times 6.023\times 10^{23}$

$\to$ Now, total Number of voids $=3\times$ total no. of atoms

$=3\times \frac{0.581}{70}\times 6.023\times 10^{23}=14.99\times 10^{21}$

$\simeq 15\times 10^{21}$