Consider a non-stoichiometric sample of ferrous oxide exhibiting a metal deficiency defect with the — Solid State Chemistry Question

💡 Solution & Explanation

To maintain neutrality against 100 $O^{2-}$ ions (total charge $-200$), the 98 Fe ions must supply $+200$ charge. Let $x$ be $Fe^{3+}$ ions. Then $(98-x)$ are $Fe^{2+}$ ions. Equation: $3x + 2(98 - x) = 200 \implies x + 196 = 200 \implies x = 4$. So, there are exactly 4 $Fe^{3+}$ ions.