How do you predict if a reaction will be exothermic or endothermic?

Answer 1

Although it is hard to predict if a reaction will be exothermic or endothermic, there are many factors that can be considered when trying to determine it. first endothermic reactions usually employ the breaking of strong bonds, and the creation of weak bonds. While exothermic reactions usually break weak bonds and create strong bonds. Sadly these are the only ways to predict if a reaction will be endothermic or exothermic, altough there are other methods that could be used that are much more complex.

Answer 2

The difference in energy between reactants and products