Question

The composition of a sample of wustite is \( \text{Fe}_{0.93} \text{O}_{1.00} \). Percentage of iron in the form of \( \text{Fe}^{3+} \) ion is nearly:

• A. \( 85 \)
• B. \( 15 \)
• C. \( 93 \)
• D. \( 7 \)

Hint:

For non-stoichiometric compounds like wustite, charge balance method is used to determine the proportion of different oxidation states.

Answer 1

The Correct Option is B

Step 1: Understanding Wustite Composition Wustite (\( FeO \)) is a non-stoichiometric compound, meaning it contains both \( \text{Fe}^{2+} \) and \( \text{Fe}^{3+} \). The given formula shows iron deficiency, indicating the presence of \( \text{Fe}^{3+} \). Step 2: Determining Iron Oxidation States Let \( x \) be the fraction of \( \text{Fe}^{3+} \). Charge balance equation: \[ (0.93 - x) \times (+2) + x \times (+3) = 1 \times (-2) \] \[ 1.86 - 2x + 3x = -2 \] \[ x = 0.14 \] Step 3: Percentage Calculation Percentage of \( \text{Fe}^{3+} \): \[ \frac{x}{0.93} \times 100 = \frac{0.14}{0.93} \times 100 \approx 15% \] Conclusion Thus, the correct answer is: \[ 15% \]