An ore of iron, wustite, is analyzed and found to have the non-stoichiometric formula . What is the — Redox Reactions and Volumetric Analysis Chemistry Question
Question
An ore of iron, wustite, is analyzed and found to have the non-stoichiometric formula $Fe_{0.93}O$ . What is the mole fraction of total iron present specifically in the form of $Fe(III)$ ions in this crystal lattice?
💡 Solution & Explanation
Let the number of $Fe^{3+}$ ions be $y$ . The number of $Fe^{2+}$ ions is $0.93 - y$ . To maintain electrical neutrality in the crystal, the total positive cationic charge must exactly equal the $-2$ charge of oxygen. Therefore, $3y + 2(0.93 - y) = 2 \Rightarrow y + 1.86 = 2 \Rightarrow y = 0.14$ . The mole fraction of $Fe^{3+}$ among all iron atoms is $0.14 / 0.93 \approx 0.1505$ .