Tuesday, March 10, 2020

Principle and Procedure of Conductometry

What is Conductometric Titration?

Conductometric titration is a kind of titration wherein the electrolytic conductivity of a sample mixture is determined continuously with the addition of a reactant. The equivalence point is the situation in which the conductivity of the reaction mixture undergoes a sudden change. The electrical conductivity of the sample solution is reliant on the number of free ions in the sample and the charge parallel to each of these ions. Conductometry has an important application in analytical chemistry, where a standard technique is conductometric titration.


Principle of Conductometry:

To determination of the ability of a substance to carry out the electric current, conductivity is used. Siemens "g" conductance is the basic unit and that is the reciprocal of resistance and which is determined in ohms. The electrical conductivity of the sample is proportional to the number of ions present in it, and thus the conductivity calculation of the solution will provide a reading.

The working principle by which conductivity is calculated in the simple system. Two conductivity plates are located in the solution and potentially applied to them and, thereafter, the current is calculated (generally ac voltage). From the current and voltage values, the conductivity can be found. Precise and constant conductivity can be measured by multiplying the conductivity by the electrode cell.

This constant conductivity is determined by the formula given below,
Gt = Gt cal { 1 + a (t - t cal) }
Where Gt is conductivity at any temperature in °C
G tcal is conductivity at a temperature of calibration in °C
a is the temperature coefficient of the solution
t cal is the temperature of calibration.

This adjustment can be done manually or automatically by calculating the temperature coefficient of the solution with the advanced conductivity meters. Automatic temperature compensation with specific temperature sensors is necessary for reliable measurement of conductance, and the sample and standard solution should be calibrated with the same temperature.

Types of Conductometric Titration:

There are generally five types of conductometric titration, mentioned as follows.
1. Acid-base titration: It is a quantitative analysis process to determine the acid or base concentration, by accurately neutralizing it by a standard solution with a recognized concentration.
2. Precipitation titration: Precipitation titration is a titrimetric method that involves the formation of precipitates throughout the process of titration.
3. Replacement titration: The metal can be determined by this method when direct or back titration does not provide a precise endpoint or when there are no appropriate indicators for molecules.
4. Redox titration (oxidation-reduction): It is a type of conductometry titration, redox titration is a reduction by an oxidizing agent. Normally, this titration involves a potentiometer or a redox indicator.
5. Complexometric titration: In this titration, the color complex is used to determine the endpoint, this is a type of volumetric analysis.

Procedure of Conductometric Titration:

  • Take 30 ml of 0.001 M HCL in a beaker (100ml).
  • Fill the burette with NaOH solution.
  • Switch on the conductivity meter.
  • Clean the conductivity cell and temperature probe with distilled water and wipe gently with tissue paper.
  • Immerse the conductivity cell in the HCL solution.
  • Press the conductivity key.
  • The device will display conductance.
  • By continuous mixing, add NaOH in HCl.
  • Note down the readings.
  • Plot the graph of conductance versus volume of NaOH.
  • Switch off the instrument and clean the conductivity cell and temperature probe.

Applications of Conductometric Titration:

  • Conductometry is also used to find the concentration of salinity and total dissolved solids (TDS).
  • The purity of water can be determined by conductometry.
  • The solubility of sparsely soluble salts such as lead sulfate, sulfate, and barium is determined by conductivity.
  • The alkalinity of freshwater can be determined by this method.
  • Conductometric titration has several applications in precipitation titration, redox titrations, acid-base titration, and complex titrations.
  • It can be used for tracing microorganisms.
  • Conductometry is used to monitor the progress of a chemical reaction.
  • The chemical equilibrium in ionic reactions can be determined by it.

The Advantages of Conductometric Titration are as Follows.

  • Conductometric titration is simple and has wide selectivity.
  • It is also suitable for complex samples, such as turbid suspension, low concentrations, and colored solutions, etc.
  • It gives precise results with minimal errors.
  • The conductometric titration is also suitable for weak acids and more dilute solutions.
  • The endpoint of some samples (colored or turbid) cannot be seen with the naked eye. In this case, conductometric titration is used.
  • The temperature remains constant throughout the process.

The Disadvantages of the Conductometric Titration are as Follows.

  • It is not possible to measure samples with high concentrations by this method.
  • It is less accurate than other methods.
  • Changes in salt levels can increase the conductivity of the solution.
  • Only a limited number of redox titrations can be performed.

Commonly asked questions on conductometric titration are as follows.

What is conductometry?
Conductometry is the determination of electrolytic conductivity to observe the progress of a chemical reaction. It is generally used to measure the total conduction of a solution.

What is the basic principle of conductometric titration?
The main principle involved in conductometric titration is that the movement of ions produces electrical conductivity. The ions movement mainly relies on the concentration of ions

What are the types of conductometric titrations?
Acid-base titration, redox (oxidation-reduction) titration, complexometric titration precipitation titration, and replacement titration are the types of conductometric titration.

What is the major advantage of conductometric titration?
The major advantage of conductometric titration is that it can determine colored or turbid solutions and can work with many diluted solutions and weak acids.

What is the major difference between conductometric titration and potentiometric titration?
The main difference between conductometric and potentiometric titration is that conductometric titration determines the electrolytic conductivity of the sample solution, while potentiometric titrations determine the potential of the sample solution.


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