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

• A. A catalyst decreases the reaction rate by raising the activation energy.
• B. A catalyst increases the reaction rate by increasing the equilibrium constant.
• C. A catalyst increases the reaction rate by lowering the activation energy.
• D. A catalyst has no effect on the reaction rate.

Answer: (C)

Verified step by step guidance

1. Understand that a catalyst is a substance that speeds up 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 reaction rate because more molecules have enough energy to overcome the energy barrier.
5. Remember that a catalyst does not change the equilibrium constant or the overall thermodynamics of the reaction; it only affects how quickly equilibrium is reached.