Final answer:
Hess's Law states that the enthalpy change of the net reaction is the sum of the enthalpy changes for the individual reactions, emphasizing that enthalpy is a state function.
Step-by-step explanation:
Harold Hess, more commonly referred to just as Hess, is known for Hess's Law in chemistry. According to Hess's Law, the enthalpy change (ΔH) for the net reaction is the sum of the enthalpy changes for the individual steps in a reaction. This is a reflection of the fact that enthalpy is a state function, which means its value is determined only by the initial and final states of the system, and not by the path taken to get from one to the other. For example, if a reaction can occur via multiple steps, the total enthalpy change for the reaction will be the same, regardless of whether it happens in one step or through several intermediate steps.
The significance of this law in chemistry and thermodynamics is profound because it allows scientists to calculate the enthalpy change for reactions that are difficult to measure directly, by using the enthalpy changes of other known reactions that share common intermediates or products.