What is a catalyst?

• A. Speeds up the rate of a chemical reaction without being consumed or changed.
• B. Is consumed in the reaction to form products.
• C. Slows down the reaction.
• D. Changes the overall energy of the reaction.

Answer: (A)

A catalyst is a substance that speeds up a chemical reaction without being consumed in the process. It works by providing an alternative pathway for the reaction with a lower activation energy, so more molecules can react at a given temperature. Because it isn’t used up, the catalyst is left unchanged and can participate again in further reactions. It does not alter the overall energy change of the reaction (the heat released or absorbed), so the end products’ energy difference remains the same. It also doesn’t shift the final equilibrium; it simply helps the system reach equilibrium faster by accelerating both the forward and reverse steps. Examples include the platinum used in catalytic converters and enzymes in biological systems, which speed up reactions without being consumed.