Chapter 10, Problem 10.113QP

Portable hot packs are available for skiers and people engaged in other outdoor activities in a cold climate. The air-permeable paper packet contains a mixture of powdered iron, sodium chloride, and other components, all moistened by a little water. The exothermic reaction that produces the heat is a very common one—the rusting of iron.

$4Fe(\text{s})+3O_2(\text{g})\to 2F{e}_2{O}_3(\text{s})$

When the outside plastic envelope is removed, O₂ molecules penetrate the paper, causing the reaction to begin. A typical packet contains 250 g of iron to warm your hands or feet for up to 4 hours. Using data from Appendix 2, determine how much heal (in kilojoules) is produced by this reaction.