Look at the enthalpy change of the reaction (
Note: Please do not be apprehensive about the long explanation. I have tried to explain the steps I have taken as simply as possible and in full. Feel free to ask further questions if you do not understand any part of the answer.
To figure out whether a reaction is exothermic or endothermic, you need to know whether it releases or absorbs energy (endothermic absorbs energy, exothermic releases energy).
To find the amount of energy that is released or absorbed by the reaction you need to find the enthalpy change (
you need to add up all of the bond energies of the bonds in the reactants and products. I used this table to get the bond energies of various types of covalent bonds, but you will probably be provided with your own. Since the values given are averages they may be different from different sources.
In the reactants there are 2
In the products there are 2