Chapter U5.10, Problem 3E

Interpretation Introduction

Interpretation: The reason of expressing heat of combustion in negative value needs to be described.

Concept introduction: Combustion reactions are used to power vehicles, heat water and homes, and create electricity. But not all combustion reactions provide the same amount of energy.

Answer to Problem 3E

Heat of combustion indicated as a negative number because energy is transferred from the system.

Explanation of Solution

Heat of reaction for a combustion reaction is usually referred to as the heat of combustion. When the reaction is exothermic heat of reaction is indicated as negative number. This is because energy is transferred from the system.

Conclusion

Heat of reaction cab indicated in kilocalories per mole, kilocalories per gram, kilojoules per mole and kilojoules per gram.