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Conductance of Electrolytic Solutions & Measurement of Conductivity of Ionic Solutions | Chemistry Class 12 - NEET PDF Download

Conductance 

Conductance/ Conductivity of Different Electrolytic SolutionsConductance/ Conductivity of Different Electrolytic Solutions

Introduction: 

Both metallic and electrolytic conductors obey Ohm's law

i.e. V = IR

where V = Potential difference in volt; I Current in ampere ; R = resistance in Ohm

We know, resistance is directly proportional to length of conductor and inversely proportional to cross sectional area of the conductor.

Conductance of Electrolytic Solutions & Measurement of Conductivity of Ionic Solutions | Chemistry Class 12 - NEET 

Specific resistance is the resistance of a conductor having lengths of 1 cm and cross sectional area of 1 cm2.

Unit of R is ohm and unit of specific resistance is ohm cm

Reciprocal of resistance is called as conductance and reciprocal of specific resistance is called as specific conductance. 

Conductance of Electrolytic Solutions & Measurement of Conductivity of Ionic Solutions | Chemistry Class 12 - NEET

where C = conductance ohm-1; K = specific conductance ohm-1 cm-1.

Ohm and siemens are other units of conductance.

Conductance of Electrolytic Solutions & Measurement of Conductivity of Ionic Solutions | Chemistry Class 12 - NEET

Specific conductance = Cell constant x Conductance.

Specific Conductance is Conductance of 1 cm3 of an electrolyte solution.

In case of electrolytic solution, the specific conductance is defined as the conductance of a solution of definite concentration enclosed in a cell having two electrodes of unit area separated by 1 cm apart.

1. Equivalent Conductance 

Equivalent conductance is the conductance of an electrolyte solution containing 1 gm equivalent of electrolyte. It is denoted by ^.

^ = K × V

( ^ = ohm-1 cm-1 × cm3 = ohm-1 cm2)

Usually concern ration of electrolyte solution is expresses as C gm equivalent per litre.

Thus, V = Conductance of Electrolytic Solutions & Measurement of Conductivity of Ionic Solutions | Chemistry Class 12 - NEET

{Volume having 1 gm equivalent electrolyte in the solution} Thus, ^ = K × Conductance of Electrolytic Solutions & Measurement of Conductivity of Ionic Solutions | Chemistry Class 12 - NEET.

2. Molar Conductance

Molar conductance may be defined as conductance of an electrolyte solution having 1 gm mole electrolyte in a litre. It is denoted by ^m.

^m = K × V

Usually concentration of electrolyte solution is expressed as 'M' gm mole electrolyte per litre.

Thus, V = Conductance of Electrolytic Solutions & Measurement of Conductivity of Ionic Solutions | Chemistry Class 12 - NEET 

Hence, ^m = K × Conductance of Electrolytic Solutions & Measurement of Conductivity of Ionic Solutions | Chemistry Class 12 - NEET

Relation between ^ and ^m^m = n × ^

Determination of ^m0 or ^0 

A plot of ^m vs as found experimentally is as shown below graphically.

Conductance of Electrolytic Solutions & Measurement of Conductivity of Ionic Solutions | Chemistry Class 12 - NEET

the ^m vs Conductance of Electrolytic Solutions & Measurement of Conductivity of Ionic Solutions | Chemistry Class 12 - NEET plot of strong electrolyte being linear it can be extrapolated to zero concentration.

Thus, ^m values of the solution of the test electrolyte are determined at various concentrations the concentrations should be as low as good.

^m values are then plotted against Conductance of Electrolytic Solutions & Measurement of Conductivity of Ionic Solutions | Chemistry Class 12 - NEET when a straight line is obtained. This is the extrapolated to zero concentration. The point where the straight line intersects ^m axis is ^ºm of the strong electrolyte.

However, the plot in the case weak electrolyte being non linear, shooting up suddenly at some low concentration and assuming the shape of a straight line parallel to ^m axis. Hence extrapolation in this case is not possible. Thus, ^0 of a weak electrolyte cannot be determined experimentally. It can, however, be done with the help of Kohlrausch's law to be discussed later.


Measurement of the Conductivity of Ionic Solutions

MOLAR IONIC CONDUCTIVITY 

The individual contribution of an ion, irrespective of the nature of the ion of the electrolyte in infinite dilution is called as molar conductivity.

QUESTION ON MOLAR CONDUCTIVITY

Conductance of Electrolytic Solutions & Measurement of Conductivity of Ionic Solutions | Chemistry Class 12 - NEET
The problems on molar conductivity is solved by above formula. In which k is the measured conductivity and c is the electrolyte solution .

UNITS OF MOLAR CONDUCTIVITY 

Units of molar conductivity is Siemens meter per molarity or Siemens meter per-square per mole.

DEFINATION OF MOLAR CONDUCTIVITY

The  conductivity produced by dissolving 1 gram-mole of an electrolyte placed between two large electrodes at one centimeter apart is called as molar conductivity.
The document Conductance of Electrolytic Solutions & Measurement of Conductivity of Ionic Solutions | Chemistry Class 12 - NEET is a part of the NEET Course Chemistry Class 12.
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FAQs on Conductance of Electrolytic Solutions & Measurement of Conductivity of Ionic Solutions - Chemistry Class 12 - NEET

1. What is conductance?
Ans. Conductance is a measure of the ability of a substance to conduct electric current. It is the reciprocal of resistance and is measured in siemens (S).
2. How is the conductivity of ionic solutions measured?
Ans. The conductivity of ionic solutions is measured by using a conductivity meter. The meter consists of two electrodes placed in the solution, and the conductance is determined by measuring the current flowing between the electrodes. The conductivity is then calculated using the equation conductivity = conductance × cell constant.
3. What are electrolytic solutions?
Ans. Electrolytic solutions are solutions that contain ions, which are charged particles. These solutions are able to conduct electricity due to the movement of these ions. Common examples of electrolytic solutions include saltwater and acidic or alkaline solutions.
4. Why is measuring the conductivity of ionic solutions important?
Ans. Measuring the conductivity of ionic solutions is important in various fields such as chemistry, biology, and environmental science. It helps in determining the concentration of ions in a solution, studying the behavior of electrolytes, monitoring water quality, and understanding the properties of different substances.
5. How does temperature affect the conductivity of ionic solutions?
Ans. Temperature has a significant effect on the conductivity of ionic solutions. Generally, as the temperature increases, the conductivity of the solution also increases. This is because higher temperatures provide more energy to the ions, allowing them to move more freely and increase the conductivity. However, this relationship may vary depending on the specific ions and their behavior in the solution.
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