Final answer:
The enthalpy change of a reaction represents the heat absorbed or released during a chemical reaction. It is determined by the energy differences between breaking bonds in reactants and forming bonds in products, indicating if a reaction is endothermic or exothermic.
Step-by-step explanation:
The change in enthalpy that occurs in the process of converting reactants to products in a chemical reaction is called the enthalpy change of reaction.
The enthalpy change is a measure of the heat absorbed or released during a chemical reaction at constant pressure. It is calculated by determining the energy required to break the chemical bonds of the reactants and the energy released upon the formation of the bonds in the products. This difference in energy shows whether a reaction is endothermic or exothermic. In endothermic reactions, more energy is absorbed to break bonds than is released when new bonds form, resulting in a positive enthalpy change. Conversely, in exothermic reactions, more energy is released during bond formation than is required to break the bonds of the reactants, leading to a negative enthalpy change.
Additionally, Hess's law is often applied to calculate the enthalpy change of a reaction, which is useful in situations where the reaction occurs through multiple steps or has intermediate products. The law states that the total enthalpy change of a process is the sum of the enthalpy changes of each step, allowing for the calculation of enthalpy change even if the overall reaction path is not directly observed.