Question

What is rust? Give the equations for the formation of rust.

Answer 1

• Corrosion of iron is known as rusting. It is a slow oxidation process of iron with atmospheric oxygen in the presence of water.
• The chemical formation of rust is:

$\underset{\mathrm{Iron}}{\underbrace{4\mathrm{Fe}\left(\mathrm{s}\right)}}+\underset{\mathrm{Oxygen}}{\underbrace{3{\mathrm{O}}_2\left(\mathrm{g}\right)}}+\underset{\mathrm{Water}}{\underbrace{6{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}}\to \underset{\mathrm{Iron}\mathrm{hydroxide}}{\underbrace{4\mathrm{Fe}{\left(\mathrm{OH}\right)}_3\left(s\right)}}$

1. Iron (III) hydroxide readily breaks down to form hydrated iron(III) oxide.
2. Rust is represented as ${\mathrm{Fe}}_2{\mathrm{O}}_3.{\mathrm{xH}}_2\mathrm{O}.$

$\underset{\mathrm{Iron}\mathrm{hydroxide}}{\underbrace{4\mathrm{Fe}{\left(\mathrm{OH}\right)}_3\left(\mathrm{s}\right)}}+\underset{\mathrm{Oxygen}}{\underbrace{{\mathrm{O}}_2\left(\mathrm{g}\right)}}\to \underset{\mathrm{Rust}}{\underbrace{{\mathrm{Fe}}_2{\mathrm{O}}_3.{\mathrm{xH}}_2\mathrm{O}\left(\mathrm{s}\right)}}$