Calculate the number of unit cells in 0.9 g metal if it forms bec structure. $\left[\rho \times \mathrm{a}^3=3 \times 10^{-22}\right.$ gram$]$

Find the void volume of fcc unit cell in $\mathrm{cm}^3$ if the volume of fcc unit cell $1.25 \times 10^{-22} \mathrm{~cm}^3$.

What type of solid is the silica?

In a solid, $\mathrm{B}^{-}$ions occupy corners of a cube forming ccp structure. If $\mathrm{A}^{+}$ion occupy half the tetrahedral voids, formula of the solid is