Specific, Equivalent and Molar Conductivity

Introduction

Various solute fractions (molar, equivalent, or ionic strength) and the specific conductances of the binary systems that make up a mixture can be put down in terms of the specific conductances of the constituent binary systems. These binary conductances are evaluated at some form of “constant” concentration that describes the combination, such as a constant temperature (constant total molarity, constant total equivalents, or constant total ionic strength). By incorporating a correction term in these formulations, it is possible to make them accurate for fitting experimental data. In order to transfer these binary approximations for the specific conductance and their related correction components to the analogous binary approximations for “concentration conductances,” such as molar, equivalent, or ionar (ionic strength) conductance, general forms have been developed. Simple binary approximations for any concentration conductance expressed in terms of arbitrary fractions for any arbitrary binary evaluation approach, on the other hand, lead to binary approximations for the specific conductance. When “natural” fractions or “natural” binary evaluation procedures are employed, the resulting forms are simpler in both instances. The specific conductance is the most fundamental of all physical properties. For the sake of illustration, the system NaCl MgCl2 H2O is employed.

Specific and molar conductance

Specific conductivity and molar conductivity are two types of conductivity. In materials, conductance is a feature of materials that allows ions to pass through them and, as a result, allows for the transmission of electricity. It is commonly described as the inverse of the resistance of the substance in question. The conductance unit in SI is denoted by the letter S. (Siemens). Specific conductivity (also known as conductivity) is a measure of a material’s capacity to conduct electricity, and it is expressed as a percentage. The letter “K” is used to symbolize this letter. As a result, by definition,

G is equal to 1/R.

R= ρl/A

К= 1/ρ

G =К A/l

Where,К = conductivity, ρ = resistivity of the material  G is the conductance.  R stands for resistance.  l is an abbreviation for length.  A is the area of the cross-section.

In a material, the conductance is determined by the nature of the substance, the number of valence electrons present in the material, and the temperature. Because of the valence electrons present in metals, they are excellent conductors of electricity. The conductivity of materials reduces as the temperature of the substance rises, as we have observed.

Because of the presence of hydroxyl ions in pure water, it is known to have extremely low conductivity in its pure state. Because electrolytes release their ions into the solution, the conductivity is further increased in the presence of electrolytes. Electricity is conducted through a solution when ions are present; this is referred to as electrolytic or ionic conductance. At a given concentration, the specific conductivity of an electrolytic solution, also known as the conductivity of an electrolytic solution at a given concentration, is the conductance of one unit volume of solution maintained between two platinum electrodes with a unit area of cross-section and at a unit distance. The conductivity of electrolytic solutions is determined by the following factors:

The type of electrolyte used, as well as its concentration, are important considerations.The size of the ions produced and the degree to which they are solvated. The nature of the solvent and its viscosity.

Because of differences in the charge, concentration, and size of the ions in which electrolytes dissolve, as well as the ease with which the ions migrate under a potential gradient, the conductivity of solutions of different electrolytes with the same solvent and at the same temperature might change. As a result, we use the more commonly used word molar conductivity to describe the conductivity of an electrolyte solution. It is defined as the conductance measured between two electrodes with unit cross-sectional area and unit distance between them when their concentrations are the same. For example, the molar conductivity of a solution at a given concentration is the conductance measured between two electrodes with unit cross-sectional area and unit distance between them. To put it another way, it can be described as the relationship between specific conductivity and concentration of the electrolyte. It is represented by the symbol m.

Ʌm= K/c

Where,

К = specific conductivity

c represents the concentration of electrolyte.

Equivalent conductance

The conductivity of a volume of solution containing one equivalent of an electrolyte is measured in equivalent conductivity units. Consider the volume of a V cm3 solution containing one electrolyte equivalent, which is represented by the symbol 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 mathematical terms, the following is the definition and formula for equivalent conductance:

the conductance of V cm3 ————- Λ

the conductance of 1 cm3 ————- κ

Therefore:

Λ = κ.V ————— equation (3)

We already know that the normalcy (N) of a solution can be calculated using the equation below.

 N = n/V 1000

The equivalent conductance formula is as follows:

V = 1000/n .

For the electrolytic solution described above, the number of equivalents is n = 1.V = K x 1000/n

In this case, the relationship between V and NEquivalent conductance can be expressed as kx V.

Units of  Λ: units of equal conductance (also known as conductance units).

The equiv-1 value is equal to cm2. mho. The equiv-1 value is also known as m2 Siemens.

Conclusion

One measure of specific conductance, also known as conductivity, is the conductance of a solution contained in a cell with two electrodes of equal area that are separated by one centimetre. In contrast to the prior case, Equivalent Conductance is a specific case that is a little different from the previous one. Equivalent conductivity refers to the conductivity of a volume of solution containing one equivalent of an electrolyte, which is measured in units of conductivity. Molar conductivity is the conductance property of a solution containing one mole of electrolyte, or a function of a solution’s ionic strength or salt concentration, and it is measured in units of one mole of electrolyte per litre of solution.