According to collision and transition state theories, which of the following statements best explains why increasing temperature generally increases the rate of a chemical reaction?

• A. Higher temperature decreases the activation energy required for the reaction.
• B. Higher temperature causes the reaction to become exothermic.
• C. Higher temperature increases the number of molecules with sufficient energy to overcome the activation energy barrier.
• D. Higher temperature increases the concentration of reactants.

Answer: (C)

Verified step by step guidance

1. Understand that the rate of a chemical reaction depends on how often and how effectively reactant molecules collide with enough energy to overcome the activation energy barrier.
2. Recall from collision theory that only molecules with kinetic energy equal to or greater than the activation energy (Ea) can successfully react when they collide.
3. Recognize that increasing temperature increases the average kinetic energy of molecules, which shifts the energy distribution so that more molecules have energy equal to or greater than Ea.
4. From transition state theory, higher temperature increases the population of molecules that can reach the activated complex (transition state), thus increasing the reaction rate.
5. Conclude that the key reason temperature increases reaction rate is because it increases the number of molecules with sufficient energy to overcome the activation energy barrier, not because it changes activation energy, reaction enthalpy, or reactant concentration.