Which of the following best describes the usefulness of catalysts in chemical reactions?

• A. They change the equilibrium position of a reaction.
• B. They are consumed during the reaction and become part of the products.
• C. They increase the yield of products by providing more reactants.
• D. They increase the rate of a reaction by lowering the activation energy.

Answer: (D)

Verified step by step guidance

1. Understand the role of a catalyst in a chemical reaction: a catalyst provides an alternative reaction pathway with a lower activation energy, which increases the rate at which the reaction reaches equilibrium.
2. Recall that catalysts do not change the equilibrium position of a reaction; they only help the system reach equilibrium faster without affecting the concentrations of reactants and products at equilibrium.
3. Recognize that catalysts are not consumed in the reaction; they remain unchanged after the reaction and can be used repeatedly.
4. Note that catalysts do not increase the amount of reactants or products; they only affect the speed of the reaction, not the overall yield or equilibrium composition.
5. Conclude that the best description of a catalyst's usefulness is that it increases the rate of a reaction by lowering the activation energy, facilitating faster attainment of equilibrium.