# Chapter 7 - Chemical Reactions and Quantities - 7.9 Energy in Chemical Reactions - Questions and Problems - Page 274: 7.91

a. Exothermic. $\Delta H = -802 \space kJ$ b. Endothermic. $\Delta H = +65.3 \space kJ$ c. Exothermic. $\Delta H = -850 \space kJ$

#### Work Step by Step

1. If the energy is in the reactants, it is an endothermic reaction, because it requires energy. If the energy is in the products, it is an exothermic reaction, because it releases energy. a. Energy in the products: Exothermic. b. Energy in the reactants: Endothermic. c. Energy in the products: Exothermic. 2. If the reaction is exothermic, $\Delta H$ is negative, if the reaction is endothermic, $\Delta H$ is positive. - The absolute $\Delta H$ is given by the energy value in each equation. a. $\Delta H = -802 \space kJ$ b. $\Delta H = +65.3 \space kJ$ c. $\Delta H = -850 \space kJ$

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