Definition

Noun: A principle in chemical kinetics stating that the rate of an elementary chemical reaction is directly proportional to the product of the concentrations (or activities) of the reactants, each raised to the power of its stoichiometric coefficient in the balanced equation.

Usage

The law of mass action is used to mathematically describe the relationship between reaction rates and the concentrations of reacting species. It is a fundamental concept for deriving rate laws and understanding chemical equilibrium.

Examples

• The law of mass action provides the foundation for the equilibrium constant expression.
• According to the law of mass action, doubling the concentration of a reactant in an elementary step will double the reaction rate.
• The chemist used the law of mass action to model the kinetics of the synthesis reaction.

Advanced Usage

• In Equilibrium: The law of mass action is applied to define the equilibrium constant (K) for a reversible reaction. At equilibrium, the ratio of the product of the concentrations of the products to the product of the concentrations of the reactants, each raised to their respective powers, is a constant.
• In Reaction Kinetics: For an elementary reaction , the rate law derived from the law of mass action is: Rate = k[A]^a[B]^b, where k is the rate constant.

Variants and Related Words

• Mass Action: Often used synonymously with "law of mass action," particularly when referring to the principle itself.
• Rate Law: A mathematical equation based on the law of mass action that describes the reaction rate as a function of reactant concentrations.
• Equilibrium Constant (K): A numerical value derived from the law of mass action that characterizes the position of equilibrium for a given reaction at a specific temperature.

Synonyms

• Principle of Mass Action

Related Concepts (Not Phrasal Verbs or Idioms)

• Chemical Kinetics: The branch of chemistry concerned with the rates of chemical reactions, where the law of mass action is a key principle.
• Chemical Equilibrium: The state where forward and reverse reaction rates are equal, described quantitatively using the law of mass action.
• Reaction Rate: The speed at which reactants are converted to products, which the law of mass action helps to quantify.

Noun

1. (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