Iron(II) oxide
Iron(II) oxide, also known as ferrous oxide, is an inorganic compound with the chemical formula FeO. It is one of several iron oxides, the others being iron(II,III) oxide (Fe3O4) and iron(III) oxide (Fe2O3). FeO is a black, non-stoichiometric solid.
Properties:
- Formula: FeO
- Molar mass: 71.8444 g/mol
- Appearance: Black powder
- Crystal structure: Cubic (NaCl type)
- Density: 5.745 g/cm3
- Melting point: 1,377 °C (2,511 °F; 1,650 K)
- Solubility: Insoluble in water
Preparation:
Iron(II) oxide can be prepared by heating iron(II) oxalate in a vacuum:
FeC2O4 → FeO + CO + CO2
Stoichiometric FeO is difficult to prepare. Typically, iron(II) oxide is non-stoichiometric, meaning the ratio of iron to oxygen atoms deviates slightly from 1:1. The composition usually ranges from Fe0.84O to Fe0.95O. This non-stoichiometry arises because Fe2+ can be easily oxidized to Fe3+, creating vacancies in the iron lattice.
Reactions:
Iron(II) oxide is unstable in air and readily oxidizes to iron(III) oxide (Fe2O3).
Uses:
Iron(II) oxide has limited uses. It is sometimes used as a pigment and as a precursor to other iron compounds. In laboratory settings, it can be used in certain redox reactions.
Safety:
Iron(II) oxide is generally considered to be of low toxicity. However, as with any chemical substance, it is advisable to handle it with care and avoid inhalation or ingestion.