Final answer:
One can determine the individual ΔH values of each reaction in a series using Hess's law or standard enthalpies of formation, as enthalpy is a state function that only depends on the initial and final states of a reaction.
Step-by-step explanation:
There are multiple ways to determine the individual ΔH values of each reaction in a series. One of the most common methods is to employ Hess's law, which asserts that the enthalpy change for an overall reaction is the sum of the enthalpy changes for the individual reactions. This law is grounded in the fact that enthalpy is a state function, which means that the change in enthalpy only depends on the initial and final states, not on the path taken to get from one to the other.
To calculate the standard enthalpy change of a reaction using Hess's law, you can reverse and combine reactions for which the enthalpy changes are known, ensuring that the substances cancel out to leave only the desired reactants and products. Another approach is to use the standard enthalpies of formation for the reactants and products; the enthalpy change of a reaction is then the sum of the enthalpies of formation of the products minus the sum of the enthalpies of formation of the reactants.