The heat of reaction is simply the change in internal energy or change in enthalpy of the reaction. And it's found using this formula. For example, let's take this equation here we have reactants and we have products. To find the heat of reaction, we simply find a change in atrial energy or change in enthalpy of the product. We find the change in entropy or, I'm sorry, enthalpy of the reactants and we subtract this from this and that will give us the heat of reaction. So recall it, enthalpy is a state function and what that basically means that the pathway taken to get to the final product or to get to the final system does not affect the final change in enthalpy.