Question

Why is FeO(s) not formed is stoichiometric composition ?

Answer 1

In this case, $O^{2-}$ ions adopt on sites and $F{e}^{2+}$ ions should occupy non- stoichiometric. This is the ideal arrangement. This oxide is always non-stoichiometric i.e., the composition of Fe2+ and O2 ions is not 1: 1. It is 0.95: 1 i.e. $F{e}_{0.95}{O}_1\left(Wustite\right)$ This composition can be obtained if a small number of $F{e}^{2+}$ ions are replaced by two-thirds of’ $F{e}^{3+}$ ions in sites. Eventually, there would be less amount of metal as compared to stoichiometric composition.