What is the number of unit cells present in $3.9 \ g$ of potassium if it crystallizes in $BCC$ structure?

$X$-rays of wavelength $1 \ \mathring{A}$ are diffracted by the planes of particles in a metal. The second-order diffraction occurs at an angle of $60^{\circ}$. Calculate the distance between two parallel planes in $\mathring{A}$.

What is the molar mass of a metal with a $BCC$ structure having a density of $10 \ g \ cm^{-3}$ and an edge length of $200 \ pm$?

Calculate the edge length of a unit cell if a metal having an atomic radius of $170 \ pm$ forms a simple cubic unit cell.

An element (atomic mass $= 60$) has a face-centered cubic $(FCC)$ structure with a density of $6.23 \ g \ cm^{-3}$. The edge length of the unit cell is.... $(N_A = 6.02 \times 10^{23} \ mol^{-1})$

Calculate the edge length of a unit cell that crystallizes to form a $BCC$ structure. (Radius of atom is $2.17 \times 10^{-8} \ cm$,$\sqrt{3} = 1.732$)