What is defined as a step-by-step description of the elementary reactions that lead to a chemical change?

A reaction mechanism is defined as a detailed, step-by-step description of the elementary reactions that occur during a chemical change. It outlines the sequence of elementary steps that make up the overall reaction, including the bonds that are broken and formed, the intermediates that may be produced, and the transition states that occur along the way. Understanding the mechanism is crucial for chemists as it provides insights into how and why a reaction occurs, allowing for the prediction and manipulation of reaction conditions.

The other choices refer to different concepts in chemistry. An equilibrium constant relates to the ratios of concentrations of products to reactants at equilibrium and does not describe reaction steps. A catalytic process involves the acceleration of a chemical reaction by a catalyst but does not provide details on the individual reactions that occur. An oxidation-reduction reaction specifically deals with the transfer of electrons between species and does not encompass the broader definition of a reaction mechanism.