Factors Affecting kohlrausch’s Law

In general, the conductance of an electrolyte is influenced by the following parameters, among others:

(1) The electrolyte’s chemical composition

(2)The concentration of the solution is defined as

(3) Thermometer readings

Nature of electrolyte

Firstly, it is important to understand the electrolyte’s nature. The conductance of an electrolyte is proportional to how many ions are present in the solution. As a result, the conductance increases in direct proportion to the quantity of ions present in the solution. The amount of ions produced by an electrolyte is determined by the type of the electrolyte. As a result of their ability to dissolve almost totally into ions in solutions, strong electrolytes exhibit high conductance in their solution compositions. When compared to strong electrolytes, weak electrolytes are dissociated to a lesser extent and produce a smaller number of ions. As a result, the conductance of solutions containing weak electrolytes is low.

Concentration of the solution

The molar conductance of electrolytic solution varies in proportion to the concentration of the electrolyte present in the solution. In general, the molar conductance of an electrolyte increases as the concentration of the electrolyte decreases or as the dilution increases.

I Variation of conductivity with concentration in strong electrolytes: When the concentration of a strong electrolyte approaches zero, i.e., when the dilution is infinite, there is a tendency for the molar conductivity to approach a certain limiting value, which is known as the limiting value of the electrolyte. The molar conductivity at infinite dilution is the molar conductivity when the concentration approaches zero (i.e., when the concentration approaches zero). It is indicated by the digit 0

As a result, when C = 0, (At infinite dilution)

In the laboratory, it has been discovered that the expression for the fluctuation of molar conductivity with concentration is valid.

Λ = Λ0 – Ac1/2

In this equation, A is a constant, and 0 is referred to as molar conductivity at infinite dilution

To investigate the relationship between molar conductivity and concentration, plot the values of m against the square root of the concentration [(√C)] on a graph. As shown in fig. 1, charts depicting the fluctuation in molar conductivity as a function of [√C] for both KCl and HCl are shown. In this study, it was discovered that the fluctuation of m with concentration, √C, is minimal (between 4 and 10% only), allowing the plots to be extrapolated to zero concentration. As a result, the molar conductance reaches its maximum value when the concentration approaches zero, which is known as the molar conductivity at infinite dilution.

To understand how weak electrolytes behave, we need to look at their molar conductivity. When opposed to strong electrolytes, weak electrolytes dissociate to a far lesser level. Thus, when compared to strong electrolytes, the molar conductivity of weak electrolytes is lower.

It should be noted that the fluctuation of m with [√C is extremely high, to the point where we cannot extrapolate the molar conductance at infinite dilution (0) by extrapolation of the [√C plots. A weak electrolyte such as CH3COOH behaves in a way that is depicted in the image.

In the case of weak electrolytes, an indirect method based on Kohlrausch rule can be used to determine the 0 value.

Variation of molar conductivity with concentration for weak electrolytes 

The variation in molar conductance with concentration can be explained by the difference in conducting abilities of ions in weak and strong electrolytes in the solution , it can be explained as follows:

The fluctuation of with dilution in weak electrolytes can be explained on the basis of the quantity of ions present in solution, as previously stated. Depending on how much dissociation occurs with dilution, the amount of ions produced by an electrolyte in solution varies. The degree of dissociation increases as the dilution is increased, and as a result, the molar conductance increases as well. This corresponds to the degree of dissociation equal to one, which means that the entire electrolyte dissociates at the limiting value of molar conductance (0).

This means that at any concentration, the degree of dissociation is computed as follows:

where indicates the degree of dissociation, c indicates the molar conductance at concentration C, and 0 indicates the molar conductance at infinite dilution.

Due to the complete ionisation of strong electrolytes in solution at all concentrations, there is no increase in the amount of ions with increasing dilution for strong electrolytes (By definition). The interionic forces, which attract ions with opposite charges in concentrated solutions of strong electrolytes, are particularly strong in concentrated solutions of strong electrolytes. Consequently, the conducting ability of ions in concentrated solutions is reduced as a result of these interatomic interactions. Because of the dilution process, the ions become increasingly far from one another and the interionic forces weaken. Dilution has the effect of increasing molar conductivity as a result. Eventually, the interionic attractions become minimal, and the molar conductance reaches the limiting value known as molar conductance at infinite dilution when the concentration of the solution becomes extremely low. Depending on the electrolyte, this value will vary.

Conductivity is dependent on temperature

The conductivity of an electrolyte increases as the temperature of the solution rises.

Ion migration 

The transmission of electricity occurs through the solution of an electrolyte, which is accomplished through the migration of ions. Therefore,

(1) Ions move at varying rates toward electrodes that are oppositely charged to one another.

(2) In electrolysis, ions are discharged or freed in equal numbers at both electrodes, regardless of how fast they are moving relative to one another.

(3) Because of the difference in the speeds of the ions, the concentration of the electrolyte changes in the vicinity of the electrode.

Conclusion

The result is that when dissociation is complete at infinite dilution, each ion, regardless of whether or not it has a substantial interaction with another ion, contributes considerably to the electrolyte’s equivalent conductance. The analogous conductivity of the electrolyte is greatly increased. If an electrolyte has the value of comparable conductance at infinite dilution, its value of similar conductance at infinite dilution is equal to the total of contributions made by each of its constituent ions (cations and anions). The ‘conductivity of ions in an electrolyte at infinite dilution is constant and does not depend on the nature of co-ions,’ according to the literature.