SQA Higher Chemistry Practice Exam

The primary function of a catalyst in a chemical reaction is to provide an alternative reaction pathway with a lower activation energy. This means that the presence of a catalyst allows the reactants to convert into products more easily and at a faster rate without being consumed in the process.

By lowering the activation energy, a catalyst increases the number of particles that possess sufficient energy to overcome the energy barrier for the reaction, leading to an increased rate of reaction. As a result, reactions that may have otherwise proceeded very slowly can occur more rapidly with the use of a catalyst.

The other options describe scenarios that do not align with the true role of a catalyst. For instance, increasing the temperature of a reaction can indeed increase reaction rates, but that is not the role of a catalyst; rather, temperature is an external factor that influences kinetic energy. Similarly, a catalyst should not provide a pathway with higher activation energy, as it would not facilitate the reaction effectively. Finally, a catalyst does not decrease the concentration of reactants; it helps facilitate the reaction without altering the concentrations.