Which of the following is the best definition of Hess' Law?

A. Since enthalpy is a state function, it will be different if a reaction takes place in one step or a series of steps.
B. Heat is always released by the decomposition of 1 mole of a compound into its constitute elements.
C. Heat evolved in a given process can be expressed as the sum of the heats of several processes that, when added, yield the process of interest.
D. The enthalpy of a process is the difference between the enthalpy of the products and the enthalpy of the reactants.
E. At constant pressure the enthalpy change of a reaction is equal to the heat change of a reaction.
I think that the answer to this is D because to find the change in heat it is the final - initial.

Well, I think it's B.

Take a look at answer C and evaluate it.

The correct definition of Hess' Law is option C. Hess' Law states that the heat evolved or absorbed in a given process can be expressed as the sum of the heats of several other processes that, when added together, yield the process of interest. This means that the overall enthalpy change of a reaction can be determined by considering the enthalpy changes of individual steps or reactions that make up the overall process.

Option D, while related to enthalpy, does not specifically describe Hess' Law. Hess' Law is about the sum of enthalpy changes, not just the difference between the enthalpies of the products and reactants in a single reaction.

So the correct answer is C.

The correct answer to the question is C. Hess' Law states that the heat evolved or absorbed in a chemical reaction is the same whether the reaction takes place in one step or through a series of intermediate steps. It also states that the heat of a reaction can be expressed as the sum of the heats of several individual processes that, when added together, yield the desired reaction.

To arrive at this conclusion, you can eliminate options A, B, D, and E through a process of elimination. Option A is incorrect because it states that the enthalpy will be different depending on whether the reaction occurs in one step or a series of steps, which is contrary to Hess' Law. Option B is incorrect because it oversimplifies the concept by stating that heat is always released during decomposition, which is not always the case. Option D is incorrect because it describes the general definition of enthalpy, not specifically Hess' Law. Option E is incorrect because it states a broader principle about enthalpy change, not specifically Hess' Law.

That leaves option C as the correct answer, as it accurately summarizes Hess' Law by stating that the heat evolved in a given process can be expressed as the sum of several processes that yield the desired reaction.