Which of the following changes will increase the rate of a chemical reaction?

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

Answer: (D)

Verified step by step guidance

1. Understand that the rate of a chemical reaction depends on factors that affect how often and how effectively reactant particles collide.
2. Recognize that decreasing the temperature generally decreases the reaction rate because particles have less kinetic energy and collide less frequently and with less energy.
3. Know that reducing the surface area of a solid reactant decreases the reaction rate because fewer particles are exposed to react and collisions occur less often.
4. Realize that adding a non-reactive gas at constant volume does not change the concentration of reactants, so it typically does not affect the reaction rate.
5. Conclude that increasing the concentration of reactants increases the reaction rate because more reactant particles are present, leading to more frequent collisions.