A catalyst in a reaction

• A. Increases the reaction rate
• B. Decreases the reaction rate
• C. Has no effect
• D. Is consumed in the reaction

Answer: (A)

A catalyst works by providing an alternate reaction pathway that has a lower activation energy. Activation energy is the energy barrier that reacting molecules must overcome to transform into products. By lowering this barrier, more collisions have enough energy to proceed to products, so the reaction happens faster. A catalyst is not consumed during the reaction, and it doesn’t change the amount of energy released or absorbed overall—the energy difference between reactants and products stays the same. It also doesn’t alter how far the reaction goes at equilibrium; it just makes the steps happen more quickly.

So the best description is that a catalyst increases the reaction rate. It doesn’t decrease the rate, isn’t unchanged, and isn’t consumed in the process.