Question

The chemical composition of rust is ____________.

Answer 1

Rust is a mixture of oxides of iron formed on the surface of iron. It is usually a reddish brown oxide formed by reaction of Iron and Oxygen in the presence of Water or air moisture.

$$\begin{gathered} 4\mathrm{Fe}\left(\mathrm{s}\right)+2{\mathrm{O}}_2\left(\mathrm{g}\right)+\mathrm{x}{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to 2{\mathrm{Fe}}_2{\mathrm{O}}_3.{\mathrm{xH}}_2\mathrm{O}\left(\mathrm{s}\right) \\ \left(\mathrm{Iron}\right)\left(\mathrm{Oxygen}\right)\left(\mathrm{Water}\right)(\mathrm{Hydrated}\mathrm{ferric}\mathrm{oxide}) \\ \left(\mathrm{Rust}\right) \end{gathered}$$

The oxidized iron is highly reactive and thus combines with water or moisture to form hydroxides which on dehydration give oxides, thus forming a reddish brown deposit of rust.

Therefore, the chemical composition of rust is Hydrated ferric oxide (${\mathbf{Fe}}_{\mathbf{2}}{\mathbf{O}}_{\mathbf{3}}\mathbf{.}{\mathbf{xH}}_{\mathbf{2}}\mathbf{O}$).