What is Kohlrausch’s Law?

In general, when an electrolyte is subjected to an infinite dilution, the equivalent conductivity of the electrolyte equals the total of its anions and cations, according to Kohlrausch’s law. When the concentration of a solution decreases, the molar conductivity of the solution increases in proportion to the decrease in concentration. In general, as the molecular conductivity of an electrolyte increases, the total volume containing a mole of the electrolyte declines towards zero, which is achieved when the concentration of the electrolyte is zero; this is known as limiting molar conductivity, abbreviated as m°.

The Kohlrausch Rule

Kohlrausch noticed that the limiting molar conductivities of various strong electrolytes followed a pattern that was consistent with his observations, which he named the Kohlrausch pattern. Based on his observations, Kohlrausch came to the conclusion that “limited molar conductivity can be represented as the sum of the contributions of anions and cations in the electrolyte,” which he considered to be a fair explanation. The Kohlrausch law, as it is more widely known, states that ions migrate in a manner that is distinct from one another. Detecting the presence of sodium in water

As an example, in order to comprehend chlorines limiting molar conductivity, it is necessary to be familiar with the limiting molar conductivities of sodium ions and chloride ions, among other things. The following are some examples of how the Kohlrausch law of independent migration of ions might be put to use in practise:

When it comes to calculating the limiting molar conductivities of electrolytes, the Kohlrausch law provides a major improvement. The molar conductivities and dissociation rates of weak electrolytes are lower than those of strong electrolytes when concentrated to high concentrations. Electrolytes with a low molar conductivity exhibit a quick increase in conductivity as the concentration of the electrolyte increases. Consequently, extrapolating the molar conductivity to zero concentration will not yield the limiting conductivity, which is a necessary but not sufficient condition.

In the case of weak electrolytes, we can calculate the limiting conductivity on an independent basis by applying the Kohlrausch law of ion migration to the electrolyte. A weak electrolyte’s molar conductivity can be determined using the Kohlrausch law formula, which can also be used for determining the dissociation constant and restricting the conductivity of the electrolyte.

α = Λ/ Ëm∘

 α = dissociation constant

Λ = molar conductivity of ion

Ëm° = limiting molar conductivity of ion

Use of Kohlrausch’s Law

• A method for evaluating the degree of dissociation is presented in detail.
• Because of their solubility, salts that are only sparingly soluble are characterised by a low solubility.
• In the presence of low-valued electrolytes, the dissociation constant is low.
• Calculations of molar conductivity for weak electrolytes using an infinite-dilution approach are performed.

History

The Kohlrausch statute, which was in effect from 1875 to 1879, was the brainchild of Friedrich Kohlrausch, who was the driving force behind it. A notable researcher in the field of electrochemistry, as well as a pioneer in the development of physical chemistry, were some of his accomplishments during his lifetime. The chemists Arrhenius, Ostwald, and Cant Hoff were the ones who exploited the law of independent migration to establish the Ironist theory, which is still used as the foundation for physical chemistry today. Arrhenius, Ostwald, and Cant Hoff were the ones who discovered the law of independent migration.

Application of Kohlrausch’s Law 

• When electrolytes are dissociated according to this constant, the electrical conductivity of the electrolytes can be computed.
• This equation can be used to determine the molar conductivity of a weak electrolyte that is limiting in its ability to carry electricity.
• It is also possible to use this law to determine the degree of dissociation that has happened in weak electrolytes when applied to weak electrolytes.
• In addition, this law is used to calculate the solubility constants of various salts, which is useful information.
• Furthermore, it is utilised by a number of electrochemical cells to compute their own potential.

Equivalent Conductivity

The conductivity of a volume of solution containing one equivalent of an electrolyte is measured in equivalent conductivity units. As a reminder, it is represented by the symbol

Consider the volume of a V cm3 solution containing a single electrolyte equivalent as a unit of measurement. It has the same conductance as a conductance that is comparable.

The conductance exhibited by a 1 cm3 solution containing this electrolyte is referred to as its specific conductance (between two electrodes with a cross-sectional area of 1 cm2 separated by a distance of 1 cm). In this section, we will go through the definition of comparable conductivity in more depth.

What Exactly Is A Cation?

A cation is an ion that has a positive charge, which implies it has more protons (positively charged particles) than electrons, which means it is more electronegative (negatively-charged particles). Whenever an atom loses one or more electrons, a cation is formed: the loss of the negatively-charged electron(s) leads to an overall positive charge due to the loss of the negatively-charged electron(s).

What Exactly Is An Anion?

When an ion has a negative charge, that means it has more electrons than protons, it is referred to as an anion. Anions are created when an atom gets one or more electrons: the gain of the negatively-charged electron(s) results in an overall negative charge due to the acquisition of the negatively-charged electron(s).

Conclusion

The conclusion is that when dissociation is complete at infinite dilution, each ion contributes significantly to the electrolyte’s equivalent conductance, regardless of whether or not it has a significant relationship with another ion. The electrolyte’s equivalent conductance is significantly increased. Any electrolyte’s value of similar conductance at infinite dilution is equal to the sum of contributions made by each of its constituent ions if the electrolyte possesses the value of comparable conductance at infinite dilution (cations and anions). As stated in the literature, the ‘conductivity of ions in an electrolyte at infinite dilution is constant and does not depend on the kind of co-ions.’