Concept:Because enthalpy is a state function, the overall change in enthalpy depends solely on the initial reactants and final products, completely independent of the route or number of intermediate steps taken.
Formula:$$ \Delta H_{\text{route 1}} = \Delta H_{\text{route 2 (step 1)}} + \Delta H_{\text{route 2 (step 2)}} $$
Solution:- This fundamental principle of thermochemistry is formally defined as Hess's Law of Constant Heat Summation.
- It states that if a chemical change occurs by multiple routes, the overall enthalpy change is identical.
Why other options are incorrect:Boyle's and Charles's laws govern the pressure, volume, and temperature relationships of ideal gases. Lussac's law governs the volume ratios of reacting gases. None of these relate to reaction enthalpy.
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