Analysis shows that FeO has a non-stoichiometric composition with formula Fe0.95O. Give reason.

Analysis shows that FeO has a non-stoichiometric composition with formula Fe0.95O. In a stoichiometric composition of FeO, there will be one Fe²⁺ ion for one O²⁻ ion. To maintain electrical neutrality, some Fe²⁺ ions are missing from the crystal lattice. Hence, the number of ions of iron is less than the number of oxide ions. The non-stoichiometry reflects the ease of oxidation of Fe²⁺ to Fe³⁺ effectively replacing a small portion of Fe²⁺ with two thirds their number of Fe³⁺. Thus for every "missing" Fe²⁺ ion, the crystal contains two Fe³⁺ ions to balance the charge. For example, 3Fe²⁺ = 2Fe³⁺ to maintain electrical neutrality.