The claim states the law of mass action, a fundamental principle in chemistry establishing that a reaction rate is proportional to the product of reactant concentrations; this is a foundational chemical truism that does not require citation.
The claim represents the fundamental Law of Mass Action, which defines elementary chemical kinetics. While advanced thermodynamic studies (such as paper [0]) discuss its limits or formulations, the core statement itself is a standard, definitional baseline of chemical science (common knowledge) rather than a contested empirical hypothesis tested by a specific paper in the list.