Final answer:
Hess's Law enables the calculation of reaction enthalpy changes using tabulated standard enthalpies of formation and other reactions, which implies that it is not necessary to conduct the reaction experimentally to determine its enthalpy change. so, option a is he correct answer.
Step-by-step explanation:
Hess's Law makes it possible for you to calculate reaction enthalpy changes using a set of tabulated data. This law states that the total enthalpy change for a reaction is the same, regardless of the number of intermediate steps taken. Therefore, it allows one to use formation reactions and other known enthalpy changes to compute reaction enthalpies for a chemical reaction without performing the reaction in a lab.
For example, to calculate the enthalpy change for the production of methane, CH4, you could use formation reactions of the reactants and products to find the overall enthalpy change. Using Hess's Law helps not only to predict the enthalpy change of the reaction but also to understand energy conservation within a chemical process.
Furthermore, Hess's Law can be applied to thermochemical cycles such as the Born-Haber cycle to calculate lattice energies for ionic solids, demonstrating its widespread utility in the field of thermochemistry.