The classification for the reaction Fe + HCl → FeCl3 + H2 is single replacement.
In a single replacement reaction, one element replaces another in a compound. In this case, iron (Fe) is reacting with hydrochloric acid (HCl), and it replaces the hydrogen (H) in HCl, resulting in the formation of iron(III) chloride (FeCl3) and hydrogen gas (H2). This type of reaction is characterized by the displacement of an element in a compound by another element.