Question

A piece of iron wire of mass 2.225g was put into a conical flaskcontaining dilute sulphuric acid. The flask was fitted with a bungcarrying a Bunsen valve, to allow the hydrogen generated to escapebut preventing air from entering. The mixture was warmed to speedup the reaction. When all the iron had reacted, the solution wascooled to room temperature and made up to 250cm^3 in a graduatedflask. With all these precautions, iron is converted to Fe^2+ ionsonly and no Fe^3+ ions are formed. 25.0cm3 of the solution wereacidified and titrated against a 0.0185 mol/dm^3 solution ofpotassium dichromate (VI). The volume required was 31.0cm^3.Calculate the percentage of iron in the iron wire.