Which factor is among the five affecting reaction rate and is typically added to speed up the process without being consumed?

• A. Concentration
• B. Temperature
• C. Nature of reactants
• D. Catalysts

Answer: (D)

A catalyst speeds up a reaction by providing an alternate pathway with lower activation energy, and it is not consumed in the process, so it can be reused to keep speeding up the reaction. This means you can add a catalyst to the mixture and, after the reaction occurs, the catalyst remains available to catalyze additional reaction events. Other factors like temperature or concentration affect rate by increasing kinetic energy or collision frequency, but they do not involve a substance that remains unchanged and active throughout the process in the same way a catalyst does. The nature of the reactants or changes in pressure can also influence rate, but the defining feature here is the presence of a substance that is not consumed while it accelerates the reaction.