Which of the following best describes the effect of a catalyst on the rate of a chemical reaction?

• A. A catalyst increases the reaction rate by raising the temperature of the reactants.
• B. A catalyst does not affect the reaction rate or activation energy.
• C. A catalyst decreases the reaction rate by increasing the activation energy.
• D. A catalyst increases the reaction rate by lowering the activation energy.

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 the rate of a chemical reaction depends on the activation energy, which is the minimum energy required for reactants to transform into products.
3. Recognize that a catalyst works by providing an alternative reaction pathway with a lower activation energy, making it easier for reactants to convert into products.
4. Note that a catalyst does not change the temperature of the reactants or the overall energy change (enthalpy) of the reaction; it only affects the activation energy.
5. Therefore, the correct description is that a catalyst increases the reaction rate by lowering the activation energy.