Which of the following statements correctly describes the effect of a catalyst on a chemical reaction?

• A. A catalyst increases the rate of reaction by lowering the activation energy, but does not change the equilibrium position.
• B. A catalyst decreases the rate of reaction and increases the activation energy.
• C. A catalyst increases the rate of reaction by increasing the temperature of the system.
• D. A catalyst increases both the rate of reaction and shifts the equilibrium toward the products.

Answer: (A)

Verified step by step guidance

1. Understand what a catalyst does in a chemical reaction: it provides an alternative reaction pathway with a lower activation energy, which increases the rate of the reaction.
2. Recall that a catalyst does not affect the overall thermodynamics of the reaction, meaning it does not change the equilibrium constant or the position of equilibrium.
3. Recognize that a catalyst does not change the temperature of the system; temperature is an external condition and not influenced by the catalyst itself.
4. Note that increasing the activation energy or decreasing the rate of reaction is the opposite of what a catalyst does, so those statements are incorrect.
5. Conclude that the correct description is that a catalyst increases the rate of reaction by lowering the activation energy but does not change the equilibrium position.