Bronsted Bjerrum Equation

Johannes Nicolaus Bronsted and Martin Lowry Bjerrum developed the Brønsted-Bjerram equation during the early 20th century. This equation established the relationship between the equilibrium constant (K) of a chemical reaction and the concentrations of acidic and basic substances in a particular solution.

The Brønsted-Bjerram equation is based on the principle of the Brønsted-Lowry theory. This equation describes the behavior of weak acids and weak bases in aqueous solutions.

The general form of Bronsted Bjerrum equation is:
log K = log Ka + C√(I) - A√(I) / (1 + A√(I))
Where,
log K is the logarithm of the equilibrium constant
Ka is the acid dissociation constant
C is the Bronsted correlation factor
I is the ionic strength of the solution
A is the Debye-Hückel constant

log Ka, represents the intrinsic strength of the acid, which is a measure of its tendency to donate protons. C√(I), considered as the effect of ionic strength on the equilibrium constant. Increasing the concentration of ions in a solution, decreases its ability to ionize and not easy for the acid to donate protons. Bronsted correlation factor(C) depends on the nature of the acid and the ions present in the solution.

A√(I), is the effect of ionic strength on the activity coefficients of the solutes. Increasing the ionic strength, decreases in the effective concentration of the solutes in solution because, the activity coefficients decrease. Thus, affects the equilibrium constant and is taken into account by the Debye-Hückel constant(A).

Applications of Bronsted Bjerrum Equation

Bronsted Bjerrum equation have may applications. Some of them are given below-
1. In acid-base titrations
2. In the study of effect of ionic strength on the equilibria of dissolved gases in water
3. In the study self-ionization of water
4. To determine the pH of solutions at different ionic strengths.