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?).
In the given reaction, the bonds in the reactants (H2 and O2) need to be broken first, and then new bonds are formed to create the product (H2O). Breaking bonds requires an input of energy, while forming bonds releases energy.
In this specific reaction, the energy required to break the bonds in the reactants (H2 and O2) is less than the energy released when the new bonds are formed in the product (H2O). This is because the reaction is exothermic, meaning it releases energy in the form of heat and light, which is observed as the explosion and ball of fire when the hydrogen balloon bursts.
So, the forming of product bonds (H2O) is higher in energy, as more energy is given off when these bonds are formed compared to the energy needed to break the reactant bonds (H2 and O2).