Define a catalyst.

Define a catalyst.

• A. A substance that increases the rate of a reaction without being consumed in the overall process
• B. A substance that is consumed in the reaction
• C. A substance that changes the equilibrium constant
• D. A substance that lowers the activation energy by increasing energy of products

Answer: (A)

A catalyst speeds up a chemical reaction without being consumed in the overall process. It does this by providing an alternative pathway with a lower activation energy, which is the energy barrier that must be overcome for the reaction to proceed. By lowering this barrier, the rate constant for the reaction increases, so reactants reach products faster. Importantly, the catalyst is regenerated at the end of the reaction, so its amount stays the same and it can catalyze many cycles. The other ideas aren’t correct for this concept: a substance that is consumed in the reaction would be a reactant, not a catalyst. A catalyst doesn’t change the equilibrium constant because it speeds up both forward and reverse reactions without shifting the final balance of products and reactants. And lowering the activation energy by increasing the energy of the products isn’t how catalysts work; they lower the energy barrier themselves, not raise product energy.

A catalyst speeds up a chemical reaction without being consumed in the overall process. It does this by providing an alternative pathway with a lower activation energy, which is the energy barrier that must be overcome for the reaction to proceed. By lowering this barrier, the rate constant for the reaction increases, so reactants reach products faster. Importantly, the catalyst is regenerated at the end of the reaction, so its amount stays the same and it can catalyze many cycles.

The other ideas aren’t correct for this concept: a substance that is consumed in the reaction would be a reactant, not a catalyst. A catalyst doesn’t change the equilibrium constant because it speeds up both forward and reverse reactions without shifting the final balance of products and reactants. And lowering the activation energy by increasing the energy of the products isn’t how catalysts work; they lower the energy barrier themselves, not raise product energy.