Which of the following best explains how catalysts increase reaction rates?

• A. They increase the concentration of reactants.
• B. They change the overall enthalpy of the reaction.
• C. They increase the temperature of the reaction mixture.
• D. They lower the activation energy required for the reaction to occur.

Answer: (D)

Verified step by step guidance

1. Understand that a catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process.
2. Recall that reaction rate depends on how quickly reactant molecules can overcome the energy barrier known as the activation energy (Ea).
3. Recognize that catalysts work by providing an alternative reaction pathway with a lower activation energy, making it easier for reactants to convert into products.
4. Note that catalysts do not change the concentration of reactants or products, nor do they alter the overall enthalpy change (ΔH) of the reaction.
5. Also understand that catalysts do not increase the temperature of the reaction mixture; temperature is an external condition that affects reaction rate independently.