What is the Significance of Standard Enthalpy of Reaction?

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The discussion centers on the concept of standard enthalpy of reaction (ΔHrO) and standard heat of formation (ΔHfO). It highlights that ΔHfO represents the net heat change during a reaction, calculated as the difference between the final and initial states. The method of calculating ΔHrO by subtracting the bond energies of reactants from those of products yields results that closely align with the ΔHfO values, indicating a strong correlation between these two approaches. This consistency suggests that both methods effectively capture the energy changes involved in chemical reactions. The underlying principles of thermodynamics and bond energies are essential to understanding these calculations.
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http://en.wikipedia.org/wiki/Standard_enthalpy_of_reaction" of reactants (ΔHfO).

My question is, why?

And I also know that I can find http://en.wikipedia.org/wiki/Standard_enthalpy_of_reaction" (ΔHrO) by subtracting the bond energies of the reactants from the products. The result differs very little from the the first method.

Also, why is that?
 
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My Answer to your First Question: The standard heat of formation of the reaction is like the "net" heat of the reaction which is "(final) minus (initial)", which is what that formula describes.
 
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