An Endothermic Reaction Involves a Net Absorption of Energy

Many chemical reactions are endothermic, such that the amount of energy released as products form is less than the amount of energy absorbed in the breaking of bonds in the reactants. An example is the reaction of atmospheric 

1 he amount of energy absorbed as the chemical bonds in the reactants break is 

Type of bond Number of moles Bond energy Total energy 

The amount of energy released upon the formation of bonds in the products is 

The amount of energy relt ased upon the formation of bonds in the products is Type of bond Number of moles Bond energy Total energy 

As before, the net energy of the reaction is found by adding the two quantities  

The positive sign indicates that there is a net absorption of energy, meaning the reaction us endothermic. For any endothermic reaction, energy can be considered a reactant and is thus sometimes includc d before the arrow of the chemical equation  

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