The iron (III) oxide formula is one of the most common formulas which students come across while studying chemistry in many classes. Normally, the use of the formula and the reactions related to its progress from basic to more complex as the students move from a lower class to higher class. Iron (III) oxide which is also referred to as ferric oxide is a chemical compound that is inorganic. It's one of the iron oxides which is vital and it contains a mineral known as hematite making it an important source of iron. This compound is also sometimes referred to as rust or hydrated ferric oxide.