An element having an atomic radius of $0.14 \ nm$ crystallizes in an $fcc$ unit cell. What is the length of a side of the cell in $nm$?

Iron oxide $FeO$ crystallises in a cubic lattice with a unit cell edge length of $5.0 \ \mathring{A}$. If the density of the $FeO$ in the crystal is $4.0 \ g \ cm^{-3}$,then the number of $FeO$ units present per unit cell is $...........$ (Nearest integer).
Given: Molar mass of $Fe$ and $O$ is $56$ and $16 \ g \ mol^{-1}$ respectively.
$N_{A} = 6.0 \times 10^{23} \ mol^{-1}$

What is the number of unit cells present in a cubic crystal lattice having $4$ atoms per unit cell and weighing $0.60 \ g$ (molar mass $60 \ g \ mol^{-1}$)?

$A$ metal $(X)$ of atomic weight $M \ g \ mol^{-1}$ crystallizes in a $bcc$ lattice. Its density is $d \ g \ cm^{-3}$. What is the equation for the unit cell edge length $(a)$? ($N=$ Avogadro number)

For a simple cubic system,find the ratio of the interplanar distances between the $(100)$,$(110)$,and $(111)$ planes.

Iron exhibits $bcc$ structure at room temperature. Above $900^{\circ}C$,it transforms to $fcc$ structure. The ratio of density of iron at room temperature to that at $900^{\circ}C$ (assuming molar mass and atomic radii of iron remains constant with temperature) is