What does Hess's Law state about enthalpy changes?

Hess's Law asserts that the total enthalpy change for a chemical reaction is the same, regardless of the number of steps taken to achieve the reaction. This principle is based on the fact that enthalpy is a state function; thus, it depends only on the initial and final states of the system and not on how the reaction occurs.

When applying Hess's Law, if a reaction can be divided into multiple steps, the enthalpy change for the overall reaction can be calculated by summing the enthalpy changes of each individual step. This means that no matter how many intermediates or steps are involved, the total enthalpy change is the cumulative result of each individual step's enthalpy change.

The other options do not capture the essence of Hess's Law. For example, while enthalpy can change with temperature, that concept pertains to the behavior of substances rather than Hess's Law itself. The notion that enthalpy is independent of the path taken is true but not as specific as the formulation of Hess's Law, which emphasizes the summation of enthalpy changes in various steps. Finally, stating that enthalpy is always a positive value is not accurate, as enthalpy can have both positive