Ostwald’s Dilution Law
Ostwald’s Dilution Law is a principle that relates degree of dissociation of a weak electrolyte with equilibrium constant of the dissociation reaction. For instance, consider the chemical equation written as follows,
HA ⇌ H+ + A–
It represents the dissociation reaction of a weak electrolyte HA (weak acid molecule). H+ and A– represent the hydrogen ion and the conjugate base ion, respectively. According to law of mass action, the equilibrium constant for the dissociation reaction would be written as,
Ka = [H+][A–]/[HA]
Ostwald’s Dilution Law states that for a weak electrolyte, the degree of dissociation (α) increases with dilution. Mathematically, it is expressed as:
α = √(Ka/C)
where,
- α = degree of dissociation
- Ka = equilibrium constant of the dissociation reaction
- C = initial concentration of the electrolyte
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.