Is Fe2O5 a correct formula of compound?

Answer 1

According to the rules for naming ionic compounds, Fe2O5 would be referred to as Iron (V) oxide.

Answer 2

It's not a correct formula and I tell you why.

We know that iron(II) oxide has the formula FeO and iron(III) oxide has the formula Fe2O3. While iron(IV) exists it isn't a dominant cation; so iron(IV) oxide doesn't exist in standard conditions.

Iron(II,III) oxide has the formula Fe3O4. Some people say it is a combination of iron(II) oxide and iron(III) oxide because FeO + Fe2O3 = Fe3O4. But this assumption isn't correct. Because Fe3O4 is an independent molecule consisting of both iron(II) and iron(III) ions. So the true formula is Fe(Fe2O4), with the first Fe being iron(II) and the second Fe being iron(III). So the ratio of iron(II)/iron(III) in this compound is 1:2 and this ratio never changes.

Note: If we want to find the oxidation state of iron in Fe3O4 without considering the iron(II) and iron(III) we obtain 8/3 as our answer which is approximately 2.66 (so it is between 2 and 3).

If we assume the formula Fe2O5, we are assuming the said ratio to be 1:1 which is incorrect.