What is Hess's Law?

Hess's Law states that the total enthalpy change of a chemical reaction is equal to the sum of the enthalpy changes for the individual steps of the reaction, regardless of the pathway taken. This principle is rooted in the fact that enthalpy is a state function, meaning it depends only on the initial and final states of a system and not on the specific steps taken to go from one to the other.

When applying Hess's Law, you can break down a complex reaction into simpler steps, and by calculating the enthalpy change for each of these steps, you can determine the overall enthalpy change for the reaction. This is particularly useful in reactions where direct measurement of the enthalpy change is difficult.

The remaining options discuss different aspects of thermodynamics. One mentions the dependence of enthalpy on the state of the system, which is true but does not encapsulate the core idea of Hess's Law. Another refers to the conservation of energy, a fundamental principle but unrelated specifically to Hess's Law. The last option describes the flow of energy in terms of temperature differences, which is a different concept entirely and does not pertain to enthalpy changes or Hess's Law. Therefore, the assertion that the sum