Chapter 24, Problem 42QP

Interpretation Introduction

Interpretation:

The value of $\Delta {\text{H}}^{\text{o}}$ for the synthesis reaction of NO is to be calculated, referring data from Appendix 2.

Concept introduction:

Enthalpy is defined as the total internal energy of the system

The enthalpy of the reaction is calculated by the expression as follows:

$\Delta H^o=\sum \Delta H_f{{}^o}_{\text{product}s}-\sum \Delta H_f{{}^o}_{\text{reactants}}$

Here, $\Delta H^o$ is the enthalpy change of the reaction and $\Delta H_f^{\text{o}}$ is the enthalpy of formation of the species.

The negative value of the enthalpy of reaction implies that the reaction is exothermic. In an exothermic reaction, change in enthalpy is negative, that is, the energy released is greater than the energy absorbed. Hence, the energy is released into the surroundings.