Specific Conductivity and Molar Conductivity - Definition, Unit, Relation, FAQs

Specific Conductivity and Molar Conductivity - Definition, Unit, Relation, FAQs

Edited By Team Careers360 | Updated on Jul 08, 2022 03:38 PM IST

Here in this article we will be discussing about conductance, conductivity, symbol of conductance, what is specific conductance, definition of specific conductivity, unit of specific conductivity, Specific conductivity of a solution, ratio of specific conductance to that of conductance, definition and relationship between conductivity and molar conductivity, what is equivalent conductivity and everything related to specific and molar conductivity will be discussed here.

What is meant by Conductance?

The term conductance is the reciprocal of resistance and it is denoted by the symbol G. Conductance can be defined as the measure of ease of current flow through a conductor. It can be given by the formula:

Conductance, G=1/R ……………(1)

In equation (1), ‘R’ is the resistance of the conductor. The unit of conductance is ohm-1 or Ω-1 and its SI unit is Siemens or S.

The conductance of a material generally depends on the following factors:

  • The nature of the metal.
  • The number of valence electrons present per atom.
  • Temperature (conductance generally decreases with increase in temperature).

Also read -

Ionic conductance

The capacity of an ion to conduct electricity is commonly defined as ionic conductance. The value of ionic conductance of a metal ion is affected by the extent of its hydration in aqueous solutions.

In the state of infinite dilution, the ionization of the electrolyte will be complete and all forces of interaction between the ions will have ceased to exist. Under such a condition, all the ions that can possibly be derived from the electrolyte under consideration are free to carry current. The motion of ionic charge causes electrical conductivity. It is called ionic conductivity or ionic conductance. Equivalent conductance, molar conductance and specific conductance are different types of conductance.

Conductivity or Specific conductance

Define specific conductance

The term specific conductance, nowadays referred to as property of any conductor which is the capacity to conduct electricity.It can be represented by the symbol ‘K’. Specific conductance gives the measure of capacity of a material to conduct electricity.

Specific conductance formula or conductivity can be given as:

1640162995997 1640162999993

In equation (2), ρ is the specific resistance.

We know that 1640162997034 1640163001170

Here in equation1640163001048’R’ indicates the resistance of a conductor of length ‘l’ 1640163000798and ‘a’ is the area of cross section in cm2.

Then,

1640163003707

Here in equation(4) ’G’ is the conductance1640163002160. Obviously if1640163003364, and 1640163002840, then equation1640162999016 becomes,

1640163003536

Thus the conductivity or specific conductance of an electrolyte solution represents the conductance with unit length and unit cross section. In other words, conductivity or specific conductance of an electrolyte solution represents the conductance of one centimeter cube of the solution kept between two ‘1640163000533’ electrodes of unit area of cross section and placed unit distance apart.

The unit of specific conductance is microsiemens/cm

  • The conductivity or specific conductance of an electrolyte depends on the following factors.
  • Nature of electrolyte – Strong electrolytes have high conductance whereas the weak electrolytes have low conductance.
  • Concentration of the solution – Molar conductance varies with concentration of the electrolyte.
  • Temperature – The conductivity of an electrolyte increases with increase in temperature.

What does the term cell constant indicate?

The term cell constant is obtained by dividing the distance between the two electrodes in a conductivity cell by the cross-section of the electrode. It is commonly expressed in the unit 1640163001583and its SI unit is1640163001278.

The expression for conductivity of an electrolyte solution is given as:

1640163001409

i.e., Conductivity 1640162997595 Conductance 1640163000121 Cell constant

The cell constant 1640162999738can also be denoted as1640163000398. Then the expression for ‘K’ becomes:

1640162996398

Hence from equation 1640162999322It is clear that the cell constant is the ratio of specific conductance and conductance.

Equivalent conductivity or Equivalent conductance

Equivalent conductivity of an electrolyte solution of a given concentration is explained as the conducting power of ions formed from one equivalent of electrolyte present in solution. It is generally denoted as1640162998305.

Specific conductance or conductivity (K) of a solution is related to equivalent conductivity by the equation:

1640162998646

Here in equation 1640162996212’K’ is expressed in 1640162997962and the concentration ‘c’ in1640162997223. Then the unit of 1640162998465is 1640162997420.

If ‘N’ is the normality of the solution and ‘K’ is expressed in 1640163004191then,

1640163003010

Also, students can refer,

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Molar conductivity or Molar conductance

Molar conductivity or molar conductance of an electrolyte solution of a given concentration can be defined as the ratio of conductivity and the molar concentration. It is denoted as1640163001983.

Specific conductance or conductivity (K) of a solution is related to molar conductivity by the equation:

1640162999463

In equation1640163003198, when ‘K’ is expressed in 1640162997787and the concentration ‘c’ in1640162994733, then the SI unit of 1640163001845 will be1640163000904.

If ‘M’ is the molarity of the solution and ‘K’ is expressed in 1640163004023then,

1640162996831 1640162999605

  • For an electrolyte solution, 1640162998138is related to 1640163001718as:

1640163002656 1640162999168

Relation between conductivity and molar conductivity

Λm=KC

C is the concentration

K is the conductivity

Λm is the molar conductivity

Also check-

NCERT Chemistry Notes:

Frequently Asked Questions (FAQs)

1. What are conductivity cells?

Various types of specially prepared cells that are used to calculate conductance. They are called conductivity cells. These cells are made of Pyrex glass and fitted with two platinum electrodes. These are welded to platinum wires fused into the bottom of two thin glass tubes containing some mercury for making contact to the circuit by means of copper wires. The glass tubes are fixed rigidly into an ebonite cover so that the distance between the electrodes remains constant.

2. What is the difference between conductivity and molar conductivity?

The term conductivity represents the measure of an electrolyte's ability to conduct electricity flowing through it whereas the molar conductivity gives the conductivity measured per unit molar concentration of an electrolyte solution.

 

 It is essential to consider the concentration of an electrolyte solution while determining the molar conductivity.

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