Molar Conductivity Variation

The conductance characteristic of a solution containing one mole of electrolyte, or is a consequence of a solution’s ionic strength or salt concentration. The graph between molar conductivity and √c (where c is the concentration) for weak electrolytes is not a straight line. At greater concentrations, weak electrolytes have lower molar conductivities and a lower degree of dissociation, which increases quickly at lower concentrations. The presence of electrolytes increases conductivity by supplying ions to the solution.

Electrolytic conductance or ionic conductance refers to the conductance of electricity by ions present in solutions. The conductance of a material is the property of a material that allows ions to flow through it and thus conducts electricity. It is commonly defined as the reciprocal of the material’s resistance.

The conductance of a material is determined by the type of the substance, the number of valence electrons in the material, and the temperature. Because of their valence electrons, metals are excellent conductors of electricity. We see that the conductivity of materials reduces as temperature rises.

Water has relatively low conductivity in its pure condition due to the presence of hydroxyl ions. The presence of electrolytes increases conductivity by supplying ions to the solution.

Friedrich Kohlrausch established that molar conductivity in dilute solutions is composed of individual ion contributions to a high degree of accuracy. This is known as the law of ion independent migration.

The conductivity of an electrolytic solution is determined by the following factors:

• The electrolyte’s nature: The amount of conduction that may occur through a material is greatly influenced by its strength and composition.
• The size of the formed ions and their solvation: The degree of disassociation that happens is influenced by the size of an ion within a substance. As a result, their conduction is influenced by their salvation characteristics.
• The solvent’s nature and viscosity: The kind of solvent and its density have an effect on a substance’s ability to conduct through it.
• Temperature (conductance increases with an increase in temperature): The temperature of a certain substance has a significant influence on conduction, which can increase or decrease. The nature and kind of metal, the number of valence electrons per atom, and the temperature of the material, on the other hand, influence conduction in metallic and electronic substances.
• Electrolyte concentration: The density and strength of a solution influence the conduction properties of a material.

The conductivity of solutions of various electrolytes varies with the same solvent and at the same temperature due to the charge, concentration, and size of the ions in which electrolytes dissolve or the ease with which the ions migrate under a potential gradient. As a result, we define molar conductivity for an electrolyte solution, which is a more frequent phrase. The conductance of a volume of solution containing one mole of electrolyte kept between two electrodes with a unit area of cross-section and distance of unit length is the molar conductivity of a solution at a given concentration. In general, it is defined as the ratio of specific conductivity to the electrolyte concentration.

Molar conductivity is the conductance characteristic of a solution containing one mole of electrolyte, or it is a consequence of a solution’s ionic strength or salt concentration. As a result, it is not a constant.

In other terms, molar conductivity may be defined as the total conducting power of all the ions generated when a mole of electrolyte is dissolved in a solution. Molar conductivity is a feature of an electrolyte solution that is primarily used to determine a certain electrolyte’s effectiveness in conducting electricity in a solution.

The following expression is used to mathematically represent molar conductivity.

λ_m = K / C

Here,

c = concentration in moles per volume

К = specific conductivity

λ_m = molar conductivity.

The unit of molar conductivity is S⋅m²⋅mol^-1.

As the solution contains only one mole of electrolyte, the above equation can be written as:

λ_m =К V

As the total volume, V, of a solution containing one mole of electrolyte grows, molar conductivity increases with decreasing concentration. The concentration diminishes with dilution. When the concentration approaches 0, the solution’s molar conductivity is referred to as limiting molar conductivity. For strong and weak electrolytes, the variation in molar conductivity with concentration is different.

Variation of molar conductivity

• With concentration for strong electrolytes:

The molar conductivity of strong electrolytes increases slowly with dilution. The plot of molar conductivity vs √c is a straight line with a y-intercept equal to λ°m. The limiting molar conductivity, λ°m, can be calculated using the graph or the Kohlrausch law.

The molar conductivity of strong electrolytes increases slowly with dilution. The plot of molar conductivity vs √c is a straight line with a y-intercept equal to λ°m. The limiting molar conductivity, λ°_m, can be calculated using the graph or the Kohlrausch law. The plot’s general equation is as follows:

λ_m = λ°_m -A√c

Where -A is a constant equal to the slope of the line. For a given solvent, the value of “A” depends on the type of electrolyte at a particular temperature.

• 

  With concentration for weak electrolyte:

The graph between molar conductivity and √c (where c is the concentration) for weak electrolytes is not a straight line. At greater concentrations, weak electrolytes have lower molar conductivities and a lower degree of dissociation, which increases quickly at lower concentrations. As a result of the limiting molar conductivity, λ°_m cannot be calculated by extrapolating molar conductivity to zero concentration. As a result, we apply the Kohlrausch law of independent ion migration to determine the molar conductivity, λ°_m, of weak electrolytes.

Specific Conductivity:

The conductance of an electrolytic solution is the ability of a particular sample to conduct an electric current. The amount to which a given sample of electrolytic solution can resist the flow of electric current is referred to as its resistance. The conductance is, of course, the reciprocal of the resistance of that specific electrolytic solution. S is the SI unit of conductance (Siemens).

FAQs

Explain what molar conductivity is.

The conducting power of all the ions is created by dissolving one mole of an electrolyte in a solution.

What effect does temperature have on molar conductivity?

As the temperature rises, so does the molar conductivity.

Is molar conductivity affected by dilution? How?

Yes, molar conductivity changes as a function of dilution. It grows stronger with dilution.

Q. What are the specific conductivity factors?

Ans: The factors are as follows:

1. Temperature
2. The size of the electrolytic ions in the solution
3. The nature of the electrolytic solution
4. The concentration of the electrolytic solution
5. The viscosity and the nature of the solvent