Homework question number 5?
Iron halides. Iron displaces hydrogen from hydrochloric acid to form pale green iron(II) chloride:
Fe(s) + 2 HCl(aq) ----->FeCl2(aq) + H2(g)
The chloride crystallizes as FeCl2�4 H2O. Exposure to air gradually oxidizes the iron(II) to FeCl3 and Fe2O3. Oxidizing FeCl2 with Cl2 produces orange-yellow FeCl3, which has metal-nonmetal bonds with covalent character.
Here's a clue: When Fe (2+) forms the metal loses two 4s electrons leaving six 3d electrons.
To form Fe (3+) the metal would lose two 4s electrons and a single 3d electron. This would leave five 3d electrons. Which is energetically more favourable under the aqueous conditions stated?
Compare this with the reaction between hot iron metal and gaseous chlorone.