What is the number of unit cells present in a cubic pack crystal lattice having 4 atoms per unit cell and…
What is the number of unit cells present in a cubic pack crystal lattice having 4 atoms per unit cell and weighing $0.60 \mathrm{~g}$ (molar mass $\left.60 \mathrm{~g} \mathrm{~mol}^{-1}\right) ?$
$1 \times 10^{21}$
$1.5 \times 10^{21}$
$3.0 \times 10^{21}$
$6.0 \times 10^{21}$
Solution
Number of moles $=\frac{0.6 \mathrm{~g}}{60 \mathrm{~g} \mathrm{~mol}^{-1}}=0.01 \mathrm{~mol}$
Total number of atoms $=0.01 \times 6.022 \times 10^{23}$
Number of atoms per unit cell $=4$ (Given)
$\therefore \quad$ Number of unit cells present in the given cubic crystal lattice
$\begin{aligned}
& =\frac{0.01 \times 6.022 \times 10^{23}}{4} \\
& =1.5 \times 10^{21} \text { unit cells }
\end{aligned}$