Question

The composition of a sample of wustite is ${Fe}_{0.93}O$. what percentage of the iron is present in the form of $Fe$ (III)?

• A. 5%
• B. 7.08%
• C. 15.05%
• D. 23.60%

Answer 1

Answer: (C)

15.05%

In pure iron oxide ($FeO$), iron and oxygen are present in the ratio 1 : 1.

However, here number of $F{e}^{2+}$ present $=$ 0.93

Or No. of $F{e}^{2+}$ ions missing $=$ 0.07

Since each $F{e}^{2+}$ ion has 2 positive charge, the total number of charge due to missing (0.07) $F{e}^{2+}$ ions $=$ $0.07\times 2$ $=$ 0.14

To maintain electrical neutrality, 0.14 positive charge is compensated by the presence of $F{e}^{3+}$ ions. Now since, replacement of one $F{e}^{2+}$ ion by one $F{e}^{3+}$ ion increases one positive charge, 0.14 positive charge must be compensated by the presence of 0.14 $F{e}^{3+}$ ions.

In short, 0.93 $F{e}^{2+}$ ions have 0.14 $F{e}^{3+}$ ions

100 $F{e}^{2+}$ ions have $=$ $\frac{0.14}{0.93}\times 100$ $=$ $15.05$%.