A chemist wants to observe the following reaction:
2H2 + O2 → 2H2O
The chemist is standing inside a room with oxygen in the air and has a balloon filled with hydrogen. The chemist holds a small flame up to the hydrogen balloon. When the balloon pops, the hydrogen explodes in a ball of fire.
Based on what you know about breaking and forming bonds, explain which part of the reaction is higher in energy (i.e., does it take more energy to break the bonds of the reactants, or is more energy given off when the product bonds are formed?). Defend your answer in three to five sentences.
In the given reaction (2H2 + O2 → 2H2O), more energy is given off when the product bonds are formed. This is because, for the reaction to proceed, the bonds of the reactants (H2 and O2) must be broken first. Breaking these bonds requires energy (endothermic process). However, when new bonds are formed between hydrogen and oxygen atoms to create water molecules (H2O), energy is released (exothermic process).
The explosion observed in the scenario (ball of fire) indicates that the energy released during the formation of product bonds (H2O) is greater than the energy required to break the reactant bonds (H2 and O2). The net effect of this reaction is an exothermic release of energy, which demonstrates that more energy is given off when the product bonds are formed compared to when the reactant bonds are broken.