Conductometric titration. :-

“Conductometric titration is a type of titration in which the electrolytic conductivity of the reaction mixture is continuously monitored as one reactant is added.” In this titration conductometer is used for measuring conductance. This is the reason it does not require any indicator as conductance or increase/decrease in ions is measured by a conductometer. That’s why it is most suitable for titration of colored solutions.

• The increase or decrease in the electrolytic conductivity of the reaction mixture is related to the change in the concentration of hydrogen and hydroxyl ions which are responsible for the conductivity.
• A sudden change in the electrolytic conductivity can lead to the inference that a stoichiometric point has been reached.

The conductometric titration graph is as shown below :-

Principle -

The principle of the conductometric titration process can be stated as follows – During a titration process, one ion is replaced with another and the difference in the ionic conductivities of these ions directly impacts the overall electrolytic conductivity of the solution.

It can also be observed that the ionic conductance values vary between cations and anions. Finally, the conductivity is also dependant upon the occurrence of a chemical reaction in the electrolytic solution.

Theory of Conductometric Titration :-

When a neutralization reaction takes place between an acid and a base, initially the conductivity of the solution is lowered due to the addition of the base. The reason behind this is that the H+ ions are replaced by the cationic part of the base. After the point of equivalence is reached, the concentration of the entities of ion increases. Hence, the conductance increases.

When plotted graphically, we can therefore observe two lines that are straight in nature with opposite slopes. The point at which these two lines meet is called the equivalence point.

Working Process of Conductometric Titration :-

The conductometric titration process or conductometry works in the following way:

• We take the titrant in a burette and the titrate in a beaker.
• Conductometer is used to measure the change in conductance against the volume of titrant being used.
• There is drop by drop addition of titrant, simultaneously conductivity is measured corresponding to the volume of titrant used.
• These measurements are plotted on the graph. The point at which there is a sharp change in conductance of the solution, that point is referred to as the Equivalence point.

Some of its major applications :-

• Conductometric titrations are used to determine water purity. It is used to check the levels of pollution present in different small water bodies like lakes, ponds or rivers.

• Conductometry can also be used to examine the salinity of seawater and the alkalinity of freshwater or freshwater bodies.

• This type of titration is used significantly in the food industry, specifically by food microbiologists, to trace various microorganisms.

• Conductometric titration can be used in determining deionized and distilled water purity or freshness by examining the equilibrium of chemicals in ionic reactions.

• It is also used largely in the pharmaceutical industries to detect many antibiotics and to check the levels of basicity in various organic acids.

Advantages and Disadvantages of Conductometric Titration :-

Some advantages of the conductometric titration process are listed below.

• This process is very useful in the titrations of very dilute solutions and weak acids.

• The end-point of this method of titration is very sharp and accurate when compared to a few other titration processes.

• This type of titration is applicable for solutions that are coloured or turbid, and for which the endpoint of the titration with normal indicators cannot be observed easily by the human eye.

• Conductometric titration has numerous applications in acid-base titrations, redox titrations, precipitation titrations, and complex titrations.

The two major disadvantages of this type of titration include:

• Only a few specific redox titrations can be done with the help of this process. This is because the conductivity of the solution is masked by relatively high hydronium ion concentration.

• The accuracy of conductometric titration is low when the concentrations of the electrolyte are high, making the titration process unsatisfactory.

Things to Remember about Conductometric Titration :-

• Conductometric Titration is the process that involves the regular addition of a reactant to the reaction mixture wherein corresponding changes in its electrolytic conductivity are observed and documented.

• Conductometric Titration is used for finding conductivity as well as the volume of the solution present.

• Relation between the size and the type of electrolyte used leads to differences in the conductivity of the solution.

• The conductometric titration works on the principle that the difference in the volume of ions leads to a difference in the conductivity of both the ions.

• The graph is the sole basis of the calculation of the equivalence point. For each electrolyte used, a different graph must be plotted.

• It is suitable for coloured solutions as well.