Chemistry - Solid State Question with Solution | TestHub

The packing efficiency of an fcc (face-centered cubic) unit cell is $74\%$.

The percentage of void space in the fcc unit cell is $100\%-74\%=26\%$.

Given the volume of the unit cell is $1.25\times 10^{-22}{\mathrm{cm}}^3$.

Void volume = $26\%$ of the volume of the unit cell

Void volume = $\frac{26}{100}\times 1.25\times 10^{-22}{\mathrm{cm}}^3$

Void volume = $0.26\times 1.25\times 10^{-22}{\mathrm{cm}}^3=0.325\times 10^{-22}{\mathrm{cm}}^3$

Void volume = $3.25\times 10^{-23}{\mathrm{cm}}^3$

Answer: $3.25\times 10^{-23}$