Chemistry 9th Edition

Published by Cengage Learning
ISBN 10: 1133611095
ISBN 13: 978-1-13361-109-7

Chapter 6 - Thermochemistry - Review Questions - Page 284: 8


Hess's Law states that the enthalpy change is constant regardless of the pathway. When a reaction is reversed, the sign changes but the magnitude is the same. When the coefficients are multiplied by a factor of $n$, the sign remains constant while the magnitude is multiplied by $n$.

Work Step by Step

If a reaction is reversed, the reaction changes from endothermic to exothermic and vice versa. Therefore, the sign would change but the magnitude does not. If we multiply the coefficients by a factor, the magnitude increases by the same scale factor as we have more reactant to produce heat. However, the sign does not change as the reaction remains exothermic or endothermic.
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