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A hand-warmer purchased by campers and skiers consists of a sealed outer plastic bag and an inner...

Question:

A hand-warmer purchased by campers and skiers consists of a sealed outer plastic bag and an inner perforated plastic bag containing powdered iron, water, salt and sawdust. When the inner bag is taken out and shaken it becomes hot because the following reaction occurs: {eq}4Fe_{(s)} + O_{2(g)} \rightarrow 2Fe_{2}O_{3(s)} \ \Delta H=823 kJ/mol {/eq}

The bag contains 15.0 g of iron that reacts completely. Calculate the energy released by the hand-warmer.

Moles of Reaction:

In chemical thermodynamics, it is common practice to indicate the amount of heat released or absorbed at the end of a chemical reaction. If the stoichiometric amounts of the reactants are different (i.e., if the coefficients of the species are not all unity), then it may be ambiguous to which of the reactants the stated quantty of heat refers. Hence, the conventional method is to report the heat associated with 'one mole of reaction'. In other words, when the reaction takes place exactly as indicated in the balanced chemical reaction, the amount of heat released or absorbed is indicated in the thermodynamic equation of reaction.

Answer and Explanation: 1

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The first task is to find the number of moles of iron that react. The quantity is given as 15.0 g, and we know that the molar mass of iron is 56...

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Endothermic and Exothermic Reactions

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Chapter 1 / Lesson 10
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Learn exothermic and endothermic reactions, their process, and the differences between them. See common endothermic vs exothermic examples.


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