Which of the following is most likely to decrease the rate of a chemical reaction?

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

Answer: (A)

Verified step by step guidance

1. Understand that the rate of a chemical reaction depends on factors such as temperature, concentration, surface area, and catalysts.
2. Recall that increasing temperature generally increases reaction rate because particles have more kinetic energy and collide more frequently and energetically.
3. Recognize that adding a catalyst lowers the activation energy, which increases the reaction rate without being consumed.
4. Know that increasing the concentration of reactants or the surface area of a solid reactant increases the frequency of effective collisions, thus increasing the reaction rate.
5. Conclude that lowering the temperature reduces the kinetic energy of particles, leading to fewer effective collisions and a decrease in the reaction rate.