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

• A. Temperature
• B. Color of the reactants
• C. Concentration
• D. Surface area

Answer: (B)

The rate of a reaction is governed by how often particles collide and how energetically those collisions occur. Temperature raises the average kinetic energy of particles, so collisions become more frequent and more energetic, speeding up the reaction. Increasing the concentration of reactants means more particles are present in the same space, leading to more collisions per second and a faster rate. For reactions involving a solid, increasing the surface area exposes more of the solid to collide with other reactants, also speeding things up.

The color of the reactants doesn’t influence how often collisions happen or how much energy they have, so it doesn’t affect the rate. Color is just a property related to light absorption/reflection, not a factor in collision frequency or energy (except in special cases where light energy drives a reaction, which is a different scenario).