Chemistry Regents Practice Test 2025 - Free Chemistry Regents Practice Questions and Study Guide

The addition of a catalyst to a chemical reaction primarily provides an alternative reaction pathway with lower activation energy. This means that the energy barrier that reactants must overcome to convert into products is reduced, allowing the reaction to occur more easily and quickly. Catalysts achieve this by stabilizing the transition state, which is the high-energy state of the reactants as they are transformed into products.

By lowering the activation energy, catalysts help increase the rate of the reaction without being consumed in the process. Importantly, using a catalyst does not alter the overall energy change of the reaction, meaning the products will still have the same energy compared to the reactants relative to their standard states.

In terms of the other choices, the addition of a catalyst does not increase the activation energy, nor does it decrease the concentration of reactants or necessarily affect the temperature required for the reaction to proceed. While catalysts can allow reactions to occur at lower temperatures compared to non-catalyzed reactions, this isn't the primary definition of their role. Overall, the fundamental effect of a catalyst is its role in providing a different pathway that requires less energy to reach the product state.