Kohlrausch Law : Introduction, Uses and Formula

Generally speaking, according to Kohlrausch law, the equivalent conductivity of an electrolyte is equal to the sum of its anions and cations when subjected to an infinite dilution. When the concentration of a solution falls, the molar conductivity of the solution rises in proportion. As the molecular conductivity of an electrolyte grows, the total volume containing a mole of the electrolyte decreases towards zero when the concentration of the electrolyte is zero; this condition is referred to as limiting molar conductivity, abbreviated as m°.

Kohlrausch law

Kohlrausch discovered that the limiting molar conductivities of various strong electrolytes followed a pattern that was consistent with his observations. Kohlrausch’s observations led him to argue that “limited molar conductivity can be described as a total of the contributions of anions and cations in the electrolyte,” which he believed was a reasonable explanation. The Kohlrausch law, as it is commonly called, states that ions travel independently of one another. Identifying the presence of sodium

For example, understanding chlorine’s limiting molar conductivity necessitates knowledge of the limiting molar conductivities of sodium ions and chloride ions. The following are some of the uses of the Kohlrausch law of independent migration of ions:

Kohlrausch law significantly improves our capacity to calculate the limiting molar conductivities of electrolytes. Weak electrolytes have lower molar conductivities and dissociation rates at high concentrations than strong electrolytes. Weak electrolytes have a rapid increase in molar conductivity as the concentration of the electrolyte increases. A consequence of this is that one cannot obtain the limiting molar conductivity by extrapolating the molar conductivity to zero concentration.

In the case of weak electrolytes, we use the Kohlrausch law of ion migration to determine the limiting conductivity on an independent basis. The Kohlrausch law formula can be used to determine the molar conductivity of a weak electrolyte, as well as to determine the dissociation constant and restrict the conductivity of the electrolyte.

α = Λ/ Ëm∘

 α = dissociation constant

Λ = molar conductivity of ion

Ëm° = limiting molar conductivity of ion

Uses Kohlrausch law

• A method for estimating the dissociation degree is described.
• The solubility of salts that are only sparingly soluble is determined by their solubility.
• The dissociation constant of electrolytes with a low value
• Molar conductivity calculations for weak electrolytes using an infinite-dilution method

History

Friedrich Kohlrausch was the driving force behind the Kohlrausch statute, which was in effect from 1875 to 1879. During his lifetime, he was a significant researcher in the field of electrochemistry, as well as a pioneer in the creation of physical chemistry. Arrhenius, Ostwald, and Cant Hoff were the chemists who exploited the law of independent migration to establish the Ironist theory, which serves as the foundation for physical chemistry today.

Application Kohlrausch law

• The electrical conductivity of electrolytes is calculated by dissociating them according to this constant.
• This equation can be used to find the molar conductivity of a weak electrolyte that is limiting.
• When applied to weak electrolytes, this law can also be utilized to identify the degrees of dissociation that have occurred.
• Additionally, this law is employed in order to compute the solubility constants of various salts.
• It is also used by a variety of electrochemical cells to compute their own potential.

Equivalent conductance

The equivalent conductance of an electrolyte is defined as the conductance of a volume of solution containing one equivalent weight of dissolved substance when placed between two parallel electrodes 1 cm apart and large enough to contain all of the solution between them when placed between two parallel electrodes 1 cm apart The value of is never directly determined, but is instead calculated from a specific conductance. If C is the concentration per cubic centimeter, the volume containing one equivalent of the solute is 1000/C, and if C is the concentration per cubic centimeter, the volume containing one equivalent of the solute is 1000/C. Due to the fact that Ls is the conductance of a centimeter cube of solution, the conductance of 1000/C cc, and hence will be equal to Ls.

Conclusion

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