Which principle states that the heat change of a reaction is independent of the path taken?

The correct answer is based on Hess's law, which asserts that the total enthalpy change for a chemical reaction is the same, regardless of whether the reaction occurs in a single step or through multiple steps. This principle relies on the idea that enthalpy is a state function, meaning that it depends only on the initial and final states of the system and not on the specific pathway taken to achieve that transition.

In practical terms, this means that if a chemical reaction can take place via different routes or mechanisms, the overall heat change will remain constant as long as the starting materials and final products are the same. Hess's law is extremely useful for calculating the enthalpy changes of reactions that are difficult to measure directly, by using known enthalpy changes of other reactions.

The other principles mentioned do not specifically address the independence of heat change with respect to the reaction path. For example, the law of conservation of energy emphasizes that energy cannot be created or destroyed, but it doesn't discuss how heat changes operate over different paths of a reaction. Bond energy relates to the energy required to break bonds in molecules, while the heat of formation principle pertains to the energy change when one mole of a compound is formed from its elements, without stating anything about the