Answer:
Hess' law states the net change of enthalpy in a chemical reaction.
Step-by-step explanation:
The change of the enthalpy happening in the chemical reaction is different of the pathway in between the initial and the final states. The addition of the equation gives the net change of the enthalpy. Enthalpy change is the amount of heat evolved or absorbed in the reaction under constant pressure. This can be calculated by checking the amount of heat evolved during the reaction. These reaction occurs at a constant pressure.