what is the law of mass action expression?
<answer> The law of mass action is the law that states the following principle: the rate of a chemical reaction is directly proportional to the molecular concentrations of the reacting substances. <context> law of mass action - (chemistry) the law that states the following principle: the rate of a chemical reaction is directly proportional to the molecular concentrations of the reacting substances. 1  law of nature, law - a generalization that describes recurring facts or events in nature; the laws of thermodynamics.