Video Transcript
Which of the following word
equations correctly describes the process of rusting? (A) Iron plus oxygen plus water
reacts to form hydrated iron(II) oxide. (B) Iron plus oxygen reacts to form
iron(III) oxide. (C) Iron plus water plus air reacts
to form hydrated iron(II) oxide. (D) Iron plus oxygen plus water
reacts to form hydrated iron(III) oxide. (E) Iron plus hydroxide ions reacts
to form hydrated iron(III) oxide plus water.
Rusting is a type of corrosion that
affects iron and some iron-containing alloys. Rusting occurs when iron is exposed
to oxygen and water, which forms a reddish-brown substance on the surface of the
metal. This substance is hydrated
iron(III) oxide, which has the chemical formula Fe2O3 nH2O. There is an n here instead of the
usual number of water molecules that are in the compound. This is because there’s a variety
of different hydrated iron(III) oxides that can form.
So the word equation that describes
rusting is iron plus oxygen plus water reacting to form hydrated iron(III) oxide,
which matches answer choice (D). Though the question didn’t ask for
it, the corresponding chemical equation is 4Fe plus 3O2 plus 2nH2O reacting to form
2Fe2O3 nH2O.
