Which of the following will lower the rate of a chemical reaction?

• A. Decreasing the concentration of reactants
• B. Increasing the temperature
• C. Increasing the surface area of a solid reactant
• D. Adding a catalyst

Answer: (A)

Verified step by step guidance

1. Understand that the rate of a chemical reaction depends on factors such as concentration of reactants, temperature, surface area, and presence of a catalyst.
2. Recall that increasing the concentration of reactants generally increases the reaction rate because more reactant particles are available to collide and react.
3. Know that increasing the temperature increases the reaction rate by providing reactant particles with more kinetic energy, leading to more frequent and energetic collisions.
4. Recognize that increasing the surface area of a solid reactant increases the reaction rate by exposing more particles to react, thus increasing collision frequency.
5. Identify that adding a catalyst lowers the activation energy, increasing the reaction rate without being consumed in the reaction, so it does not lower the rate.