2.34 describe the conditions under which iron rusts

Rusting ONLY occurs when iron is in contact with both water and oxygen (from the air). The chemical reaction that is taking place is oxidation of iron to form iron(III) oxide (oxidation reaction), water then bonds to the iron(III) oxide and forms hydrated iron(III) oxide - this is rust.

NOTE: I'm not sure if we need the word equation so here it is just incase...

iron + oxygen ---> iron(III) oxide

iron(III) oxide + water ---> hydrated iron(III) oxide