FeO crystallizes in the cubic system, in which there is four formula units in each unit cell. The de — Solid State Chemistry Question

💡 Solution & Explanation

Molar mass of FeO = $56 + 16 = 72$ g/mol. Density = $\frac{Z \times M}{N_A \times a^3} \implies 4.0 = \frac{4 \times 72}{6 \times 10^{23} \times a^3}$. $a^3 = \frac{288}{24 \times 10^{23}} = 120 \times 10^{-24}$ cm$^3$. $a = \sqrt{120} \times 10^{-8}$ cm $\approx 4.93$ Å. Therefore, correct answer is C.