Q. In orthorhombic, the value of $a,\ b$ and $c$ are respectively 4.2$\mathring{\mathrm{A}}$, 8.6 $\mathring{\mathrm{A}}$ and 8.3$\mathring{\mathrm{A}}$. Given the molecular mass of the solute is 155 g $mol^{- 1}$ and that of density is 3.3 g/cc, the number of formula units per unit cell is
A) 2
B) 3
C) 4
D) 6
Explanation
(c)
$Z = \frac{a^{3}\ \times \ N_{A}\ \times \ \rho}{M}$
$= \frac{4.2\ \times \ 8.6\ \times \ 8.3\ \times \ 10^{- 24} \times \ 6.023\ \times \ 10^{23\ } \times \ 3.3}{155} = 3.84 = 4$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.