Example of Law of Mass Action
Let us see that how law of mass action can be applied to obtain expression for a practical reaction. Consider the following chemical equation which represents the dissociation of ammonium chloride (NH4Cl) in water.
NH4Cl (aq) ⇌ NH4+(aq) + Cl–(aq)
According to law of mass action, equilibrium constant for above reaction would be,
Keq = [NH4+][Cl–]/[NH4Cl]
where, [NH4+] and [Cl–] are the concentrations of ions and [NH4Cl] is the concentration of ammonium chloride at equilibrium.
Similarly, one can obtain expression of equilibrium constant for any chemical reaction using the law of mass action.
Law of Mass Action
Law of Mass Action relates to the rate of a chemical reaction. It states that the rate of a reaction is directly proportional to the concentrations of its reactants. More precisely, the rate of a chemical reaction is directly proportional to the product of its reactant concentrations raised to their respective stoichiometric coefficients at constant temperature and pressure. This implies that an increase in reactant concentration would lead the reaction to move forward at a faster rate. The law of mass action forms the basis for equilibrium constant expression, which helps in quantifying the dynamics of the reaction.
In this article, we will discuss what is meant by the Law of Mass Action, Equilibrium Constant, Chemical Equilibrium, applications of the law and related frequently asked questions.