Iron(III) oxide

Iron(III) oxide, also known as rust, is a reddish substance, an iron oxide. It has a chemical formula of Fe2O3. It is made by the reaction of iron with oxygen. It is found naturally in the ground. It is a major ore of iron (iron comes from this mineral) as haematite. It dissolves in acids.

The iron is in the +3 oxidation state, which is what the III means. If the iron was in the +2 oxidation state, it would be iron(II) oxide.

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