Which of the following best describes how a catalyst affects the rate of a chemical reaction?

• A. It has no effect on the reaction rate.
• B. It increases the reaction rate by lowering the activation energy.
• C. It decreases the reaction rate by increasing the activation energy.
• D. It increases the reaction rate by increasing the concentration of reactants.

Answer: (B)

Verified step by step guidance

1. Understand that a catalyst is a substance that changes 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 lowering the activation energy increases the number of effective collisions per unit time, thereby increasing the reaction rate.
5. Conclude that a catalyst does not change the concentration of reactants or products, nor does it increase activation energy; it specifically increases the reaction rate by lowering the activation energy.