The distance between two parallel $(111)$ planes in a crystal with an edge length of $300 \, pm$ is ................ $pm$.

Calculate the number of unit cells in $10 \, g$ of $CsCl$ which crystallizes in a $bcc$ structure. $(CsCl = 168.5 \, amu)$

Niobium crystallises in a body-centred cubic $(bcc)$ structure. If the density is $8.55 \, g \, cm^{-3}$,calculate the atomic radius of niobium using its atomic mass $93 \, u$.

Iron exhibits $bcc$ structure at room temperature. Above $500^{\circ} C$,it transforms to $fcc$ structure. Find the ratio of the density of iron at room temperature to that at $500^{\circ} C$. (Assume the atomic radii and the molar mass of iron remain constant even with variation in temperature)

An element has an $fcc$ structure. If $200 \ g$ of this element contains $4.12 \times 10^{24}$ atoms and the density of the element is $7.2 \ g \ cm^{-3}$, calculate the edge length of the unit cell.

Sodium crystallizes in $bcc$ structure with radius $1.86 \times 10^{-8} \text{ cm}$. What is the edge length of unit cell of sodium?