How many unit cells are present in a $1.00 \ g$ cube of ideal $NaCl$ crystal?

$A$ diatomic molecule $X_2$ has a body-centred cubic (bcc) structure with a cell edge of $300 \ pm$. The density of the molecule is $6.17 \ g \ cm^{-3}$. The number of molecules present in $200 \ g$ of $X_2$ is (Avogadro constant $N_A = 6 \times 10^{23} \ mol^{-1}$) (in $N_A$)

An element crystallises in a $fcc$ lattice with cell edge $250 \ pm$. Calculate the density of the element (atomic mass $= 90.3 \ g \ mol^{-1}$) (in $g \ cm^{-3}$)

$A$ solid has a $bcc$ structure. If the distance of nearest approach between two atoms is $1.73 \, \mathring{A}$, the edge length of the cell is ........... $pm$.

Copper crystallises into a $fcc$ lattice with edge length $3.61 \times 10^{-8} \, cm$. Show that the calculated density is in agreement with its measured value of $8.92 \, g \, cm^{-3}$.

An element crystallises in $fcc$ type of unit cell. The volume of one unit cell is $24.99 \times 10^{-24} \ cm^{3}$ and density of the element is $7.2 \ g \ cm^{-3}$. Calculate the number of unit cells in $36 \ g$ of a pure sample of the element.