A Level Chemistry OCR Practice Exam 2025 - Free Chemistry Practice Questions and Study Guide

A catalytic reaction is characterized by the involvement of a catalyst, which is a substance that speeds up the reaction rate without being permanently altered in the process. Catalysts work by providing an alternative reaction pathway with a lower activation energy, thereby allowing more reactant molecules to have enough energy to undergo the transformation.

In many chemical processes, catalysts can significantly enhance the efficiency and speed of the reaction. They are essential in various industrial applications, such as in the Haber process for ammonia synthesis or in catalytic converters in vehicles, where they help convert harmful gases into less harmful ones.

Other types of reactions like addition, activation, or redox reactions do not inherently require a catalyst to occur, although some of them can be catalyzed under specific conditions. However, the defining feature of a catalytic reaction is the prominent role of the catalyst in accelerating the reaction, making this choice the most accurate.