Which of the following changes increases the rate of a chemical reaction?

• A. Decreasing the temperature
• B. Reducing the surface area of a solid reactant
• C. Increasing the concentration of reactants
• D. Adding an inert gas at constant volume

Answer: (C)

Verified step by step guidance

1. Understand that the rate of a chemical reaction depends on factors that affect how often and how energetically reactant particles collide.
2. Recall that increasing temperature generally increases reaction rate because particles move faster and collide more energetically, so decreasing temperature would decrease the rate.
3. Recognize that reducing the surface area of a solid reactant decreases the available area for collisions, thus decreasing the reaction rate.
4. Know that increasing the concentration of reactants increases the number of particles in a given volume, leading to more frequent collisions and a higher reaction rate.
5. Understand that adding an inert gas at constant volume does not change the concentration of reactants, so it does not affect the reaction rate.