DebyeHückellimietwet

The Debye-Hückel limiting law, also known as the Debye-Hückel-Onsager limiting law, is a fundamental principle in physical chemistry and electrochemistry that describes the behavior of electrolytes in solution. It was developed independently by Peter Debye and Erich Hückel in 1923, and later extended by L. Onsager in 1924. The law is particularly useful for understanding the properties of dilute electrolyte solutions, where the concentration of ions is low.

The Debye-Hückel limiting law states that the mean activity coefficient of an electrolyte in a dilute solution is inversely proportional to the square root of the ionic strength of the solution. The ionic strength is a measure of the total concentration of ions in the solution, taking into account the charge of each ion. This relationship is expressed mathematically as:

gamma_i = exp(-|z_i| * sqrt(I) / (1 + sqrt(I)))

where gamma_i is the mean activity coefficient of ion i, z_i is the charge of ion i, and I is the ionic strength of the solution.

The Debye-Hückel limiting law is based on the assumption that the ions in the solution are point charges and that the solvent is a continuous dielectric medium. It also assumes that the ions are distributed randomly in the solution, which is a reasonable approximation for dilute solutions. The law is valid only in the limit of infinite dilution, where the concentration of ions approaches zero.

The Debye-Hückel limiting law has been widely used in various fields of chemistry and physics, including electrochemistry, colloid chemistry, and biochemistry. It provides a simple and accurate description of the behavior of electrolytes in dilute solutions, and has been instrumental in the development of modern theories of electrolyte solutions. However, it is important to note that the law is not valid for concentrated solutions, where the interactions between ions become more significant. In such cases, more sophisticated theories, such as the Debye-Hückel theory for concentrated solutions, must be used.