Humber Admissions Practice Test

Which factor does NOT influence the rate of a chemical reaction?

1. Presence of a catalyst

2. Surface area of reactants

3. Color of reactants

4. Concentration of reactants

The correct answer is: Color of reactants

The choice that indicates a factor that does not influence the rate of a chemical reaction is indeed the color of reactants. The rate of a chemical reaction is primarily affected by factors such as the presence of catalysts, surface area of the reactants, and the concentration of reactants. Catalysts work by lowering the activation energy required for a reaction, thus increasing the rate at which reactants convert to products. The surface area of reactants is significant as well; for solid reactants, increasing the surface area (such as by grinding them into a powder) allows for more collisions between particles, which can increase the reaction rate. Concentration is also a crucial factor; higher concentrations of reactants typically lead to an increased number of collisions, resulting in a higher reaction rate. In contrast, color does not play a role in the speed at which a reaction occurs. The color of substances provides information about their properties but does not influence their reactivity or the kinetics of the reaction itself.