The heat pad contains iron powder and water absorbed within the pad. While sealed, the rusting reaction cannot take place. What further reactant is needed which only comes into play when the sealed packaging is opened?

Rust is hydrated iron (III) oxide. What is the chemical formula of iron (III) oxide?

$$\begin{gathered} \mathrm{A}: {\mathrm{Fe}}_2{\mathrm{O}}_4 \\ \mathrm{B}: {\mathrm{Fe}}_2{\mathrm{O}}_2 \\ \mathrm{C}: {\mathrm{Fe}}_2{\mathrm{O}}_3 \end{gathered}$$

(Enter your correct answer as $\mathrm{A}, \mathrm{B} \mathrm{or} \mathrm{C}$)

Complete the equation for the formation of rust.

$\mathrm{\_\_Fe} + \_\_{\mathrm{O}}_2 +2{\mathrm{xH}}_2\mathrm{O} \to {\mathrm{\_\_Fe}}_2{\mathrm{O}}_3.{\mathrm{xH}}_2\mathrm{O}$