Which of the following does NOT affect the rate of a chemical reaction?

• A. Temperature
• B. Surface area
• C. Presence of catalysts
• D. Amount of mass lost

Answer: (D)

The rate of a chemical reaction is governed by how often and how energetically particles collide to form products. Temperature raises the average kinetic energy of molecules, so collisions are more frequent and more likely to have enough energy to overcome the activation barrier, speeding up the reaction. Increasing surface area, especially for reactions involving a solid and a liquid or gas, exposes more particles to collide, increasing the number of effective collisions and thus the rate. A catalyst provides an alternative, lower-energy pathway to the products, so more collisions result in reaction rather than returning to reactants, which also speeds up the rate.

Mass lost, on the other hand, doesn’t drive the speed of the reaction itself. It’s an observation that can occur if gas products escape the system, but changing how much mass is lost doesn’t alter the underlying collision frequency or energy distribution that controls the rate.