Question

Give the chemical formula of rust.

Answer 1

Rust:

• The rusting of Iron can be characterized by the formation of a layer of a red, flaky substance that easily crumbles into a powder.
• The rust is hydrated Ferric oxide$({\mathrm{Fe}}_2{\mathrm{O}}_3.{\mathrm{nH}}_2\mathrm{O})$
• It is formed from a redox reaction between Oxygen and Iron in a moisture environment. That is,

$\underset{\mathrm{Iron}}{4\mathrm{Fe}\left(s\right)}+\underset{\mathrm{Oxygen}}{3{\mathrm{O}}_2\left(\mathrm{g}\right)}+\underset{\mathrm{Water}}{3{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}\to \underset{\mathrm{hydrated}\mathrm{Ferric}\mathrm{oxide}\left(\mathrm{rust}\right)}{2{\mathrm{Fe}}_2{\mathrm{O}}_3.{\mathrm{H}}_2\mathrm{O}\left(\mathrm{s}\right)}$

• The rusting of Iron is a chemical change and we can't get back pure Iron from rusted Iron by reversing the conditions.

Therefore, the chemical formula of rust is hydrated Ferric oxide$({\mathrm{Fe}}_2{\mathrm{O}}_3.{\mathrm{nH}}_2\mathrm{O})$.