Applications of Kohlrausch Law

The conduction of electricity forms the basis of many phenomena we observe in today’s world. Even the fact that we can see and identify objects around us relies on the conduction of electricity from our optic nerve to the neurons in the brain. Without the conduction of electricity, the world would be a completely barren and dead land. Kohlrausch law is one of the important laws that explain the phenomenon of the transfer of electricity.

The conduction of electricity is usually attributed to the movement of electrons. While this conclusion holds for solids, it is not appropriate for the conduction of electricity in liquids. In liquids, the movement of electrons is not possible. Instead, the transfer of electricity takes place due to ions. The dissociation of molecules results in the formation of positively or negatively charged molecules called ions.

Molar Conductivity

A liquid that conducts electricity is called an electrolyte. It contains ions that are formed due to the splitting of the compounds present in the liquid. Every electrolyte differs in its capacity to allow the electric current to pass through it.

Two broad classifications are made in regards to the strength of an electrolyte. Electrolytes can be classified into either strong or weak electrolytes. The strength of an electrolyte refers to the degree to which an electrolyte will undergo dissociation when an electric current is passed through it to facilitate its conduction.

Strong electrolytes split or dissociate into ions easily, which means electricity is easily transferred through a strong electrolyte. But in a weak electrolyte, the passing of an electric current does not cause a large amount of dissociation, which means that it is tougher to pass electricity through a weak electrolyte.

A universal measure is required to gauge the conduction capacity or conductivity of an electrolyte. Hence, we consider molar conductivity whenever we talk about the capacity of an electrolyte to conduct electricity. Every electrolyte has a specific conductance dependent on its nature and composition. By dividing the specific conductance with the molar concentration of the electrolyte, we can obtain the molar conductivity of the electrolyte.

λ=κ/c

here, λ= Molar Conductivity

κ= Specific Conductance of the electrolyte

c= Molar concentration of the electrolyte

From the equation, we can observe that molar conductivity has a direct relation with specific conductance. Hence, with an increase in specific conductance, the molar conductivity of an electrolyte will also increase. The molar concentration of an electrolyte has an inverse relation with molar conductivity, and therefore, with an increase in concentration, the molar conductivity of an electrolyte will decrease.

Kohlrausch Law

To determine with what efficiency the conduction of electricity takes place in an electrolyte, the molar conductivity of an electrolyte when the dilution approaches infinity is often used. When the dilution of an electrolyte is near infinity, it essentially means that the concentration of ions in the electrolyte is almost near to zero. In such a condition, the electrolyte’s molar conductivity is termed as limiting molar conductivity.

Limiting molar conductivity can be found with the use of a simple equation that is given by the Kohlrausch Law. Kohlrausch’s law gives a relation between the constituent ions in an electrolyte and its limiting molar conductivity.

According to the Kohlrausch Law, the sum of the limiting molar conductivities of each of the constituents in an electrolyte gives the limiting molar conductivity of that electrolyte. This relation holds a significant impact in understanding important phenomena like the dissociation of an electrolyte into its constituents.

An important condition for Kohlrausch Law is that the dilution of the electrolyte must be very near to infinity. This is because as an electrolyte approaches infinite dilution, it completely dissociates into its ions. Therefore, at infinite dilution, an electrolytic solution can be considered to have only ions and no neutral molecules.

Applications of Kohlrausch Law

At infinite dilution, Kohlrausch Law gives the limiting molar conductivity of an electrolyte. This law is used to understand the four important properties of electrolytes.

Dissociation Constant & Degree of Dissociation

The dissociation constant is a special equilibrium constant that gives a measure of how easily an electrolyte can dissociate into its constituents. By using the Kohlrausch law, this constant value can be found out, which in turn can help in the understanding of the bonds in an electrolyte. A small constant value implies a stronger bond, while a large constant value implies vice versa.

Limiting Molar Conductivity

Most of the electrolytic solutions in all types of practical usage are near-infinite dilution. Therefore, knowledge of their limiting molar conductivity can be useful when used in experiments, batteries, etc. Using Kohlrausch’s law, finding out the limiting molar conductivity becomes easier.

Solubility Constants of Salt

Electrolytes usually exist in solid form as salts. Electrolytic solutions are formed by dissolving these salts in a solvent like water. The amount of salt that can be completely dissolved in a given amount of solvent is given by the solubility constant of the salt. The higher the solubility constant, the higher the amount of salt that can be dissolved. Any salt dissolves in a solvent by dissociating it into ions. Therefore, Kohlrausch law is used to identify the degree to which salt can dissociate into ions to dissolve in a solvent.

The Cell potential of Cells

Cells or batteries have electrolytes in them, which produce ions that move to generate electricity. The electricity generated by the battery is limited by the cell potential of the battery. If the electrolytes have higher limiting molar conductivity, their cell potential is higher, which means they can generate a larger amount of electricity.

Conclusion

The conduction of electricity in liquids is not due to the movement of electrons but rather due to the movement of ions. Every electrolyte differs in its capacity to allow electric current to pass through it. Two broad classifications are made in regards to the strength of an electrolyte. Electrolytes can be classified into either strong or weak electrolytes. The strength of an electrolyte refers to the degree to which an electrolyte will undergo dissociation when an electric current is passed through it to facilitate its conduction.

To determine with what efficiency the conduction of electricity takes place in an electrolyte, the molar conductivity of an electrolyte when the dilution approaches infinity is often used. When the dilution of an electrolyte is near infinity, it essentially means that the concentration of ions in the electrolyte is almost near to zero. In such a condition, the electrolyte’s molar conductivity is termed as limiting molar conductivity.

Kohlrausch’s law has simplified the understanding of how electrolytes transfer electricity through the movement of ions. By using Kohlrausch law, important properties of electrolytes can be easily uncovered and understood. The application of Kohlrausch law is widespread and covers cells, salts, etc. The application of Kohlrausch law is important in understanding the properties of dilute solutions and also the working of electrolytic cells.