Which of the following would not be considered a reactant in a chemical reaction?

A reactant in a chemical reaction is defined as any starting substance that undergoes a transformation. The original substances that initiate a reaction are essential because they provide the necessary components that change into different substances, known as products, once the reaction has occurred.

In this case, products are formed after the reactants have been transformed through the chemical reaction. They are the end result and are not involved in the initial stages of the reaction, which is why they are not considered reactants.

Catalysts also play a specific role in a chemical reaction; they facilitate the reaction without undergoing any permanent change themselves. While they are critical for some reactions to take place, they do not partake in the reactant's definition since they are not consumed or permanently altered by the reaction process.

Thus, the correct identification of products helps reinforce a clear understanding of the different stages and components of a chemical reaction.