Question

The composition of a sample of wustite is $F{{e}_{0.92}}O$. What percentage of iron is present in the form of Fe(III)?
A. 5%
B. 7.08%
C. 15.05%
D. 23.60%

Answer 1

Wustite is a mineral form of iron oxide found with meteorites and native iron. It is grey in color and gives a greenish tint while reflected. It is found in the isometric-hexoctahedral crystal system which is opaque to metallic grains.

Complete answer:
We know that in pure form of iron oxide represented by the chemical formula$FeO$, iron and oxygen are present in the ratio 1 : 1.
However we can also conclude that here number of $F{{e}^{2+}}$ present is given i.e. 0.93 and we can say that number of $F{{e}^{2+}}$ ions missing will be 0.07.
This concludes that each $F{{e}^{2+}}$ ion has 2 positive charge thus the total number of charge due to missing $F{{e}^{2+}}$ ions will be $0.07\times 2=0.14$
Now, to maintain electrical neutrality these 0.14 positive charges are compensated by the presence of $F{{e}^{3+}}$ ions.
Now we know that replacement of one $F{{e}^{2+}}$ ion by one $F{{e}^{3+}}$ion will increases one positive charge i.e. 0.14 positive charge must be compensated by the presence of 0.14 $F{{e}^{3+}}$ ions.
In an easy manner we can say that 0.93 $F{{e}^{2+}}$ ions have 0.14 $F{{e}^{3+}}$ions.
Thus 100 $F{{e}^{2+}}$ ions have = $\dfrac{0.14}{0.93}\times 100=15.05$.

Thus, option C is the correct answer.

Note:
Wustite was an important component in the past times like in ancient times like when blacksmithing was performed using a charcoal forge then deep charcoal pit in which the steel or iron was placed which provides a highly reducing, virtually oxygen-free environment, and produces a thin wustite layer on the metal.