1. Action of air:
Dry air has no effect on iron but most air forms a brown layer of hydrated ferric oxide called Rust.
2Fe + O2 + xH2O → Fe2O3.xH2O
Hydrated ferric oxide (Rust)
2. Action of water:
Cold water does not react with iron but when steam is passed over red hot iron,H2 gas is displaced.
Fe+H2O → Fe3O4 + H2
Red -hot steam Ferrosoferric oxide
3. Reaction with non-metals:
Iron reacts directly with non-metals like halogens, sulphur carbon etc. to give respective compounds.
2Fe + 3Cl2 → 2FeCl3
Fe + S → Fes
3Fe + C → Fe3C
Iron carbidc or cementite.
4. Reaction with carbon monoxide:
Iron reacts with CO at 1200C forming iron penta carbonys.
Fe + 5CO 120 → Fe (CO)5
5. Reaction with acids:
With dil. HCl and dil. H2SO4, iron gives ferrous salt along with H2 gas.
Fe + 2HCl → FeCl2 + H2
Fe + H2SO4 → FeSO4 + H2
with hot and conc. H2SO4, iron gas a mixture of ferrous sulphate and ferric sulphate.
Fe + 2H2SO4 → FeSO4 + SO2 + 2H2O
2Fe + 2H2SO4 → Fe2 (SO4)3 + SO2 + 2H2O
with dil HNO3, iron give nitrate and ammonium nitrate
4Fe + 10HNO3 → 4Fe (NO3)2 + NH4NO3 + 3H2O
with mod conc. HNO3, iron gives Ferric nitrate and NO2 (Nitrogen dioxide).
Fe + 6HNO3 → Fe (NO3)3 + 3NO2 + 3H2O.
with hot and conc. HNO3, Iron does not react due to formation of an inert large of Fe3O4. This is called passivity of iron.