JAMB Chemistry 2024 Paper

Concept:Rust is the hydrated form of iron(III) oxide, which forms when iron reacts with oxygen and water.Explanation:Rust is not just a simple iron oxide. It contains water molecules as part of its structure.The general chemical formula of rust is $\mathrm{Fe_2O_3}\cdot x\mathrm{H_2O}$.This compound is known as hydrated iron(III) oxide.The rusting reaction can be represented as:$$4\mathrm{Fe} + 3\mathrm{O_2} + x\mathrm{H_2O} \rightarrow 2\mathrm{Fe_2O_3}\cdot x\mathrm{H_2O}$$Therefore, the rust on the surface of a metal sheet is hydrated iron(III) oxide, not hydrated iron(II) oxide or simple iron(III) hydroxide.Answer:B. hydrated iron(III)oxide