Question

Chemically rust is:

• A. Hydrated ferrous oxide
• B. Hydrated ferric oxide
• C. Only ferric oxide
• D. None of these

Answer 1

The correct option is B

Hydrated ferric oxide

The explanation for the correct option

(B) Hydrated ferric oxide

Rust

1. Rust is the hydrated form of ferric oxide $\left({\mathrm{Fe}}_2{\mathrm{O}}_3\right)$.
2. The rusting of iron $\mathrm{Fe}$ can be seen by the formation of a flaky, red layer that can easily crumble into a powder.
3. The chemical formula of rust is ${\mathrm{Fe}}_2{\mathrm{O}}_3.{\mathrm{xH}}_2\mathrm{O}$.

$4\mathrm{Fe}\left(\mathrm{s}\right)+3{\mathrm{O}}_2\left(\mathrm{g}\right)+2{\mathrm{xH}}_2\mathrm{O}\to 2{\mathrm{Fe}}_2{\mathrm{O}}_3.{\mathrm{xH}}_2\mathrm{O}\left(\mathrm{s}\right)$

Therefore the chemical formula of rust is ${\mathrm{Fe}}_2{\mathrm{O}}_3.{\mathrm{xH}}_2\mathrm{O}$ (Hydrated ferric oxide). Hence, option (B) is correct.