Richard Harwood and Ian Lodge Solutions for Chapter: Chemical Reactions, Exercise 5: Exercise 4.5

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.

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

The hot pad also contains salt. Why is this present as a component of the reacting mixture? 

Ammonium nitrate used in cool packs; give another use of it.

Give one advantage and disadvantage of the instant cool pack.

Cool packs can be used to keep vaccines and other medicines cool in hot climates. A temperature of $5°\mathrm{C}$is usually required. Devise an experiment to discover how much ammonium nitrate and how much water would have to be used to produce the temperature of $5°\mathrm{C}$needed to keep a vaccine cool in hot desert conditions.