Conductometric Titration

The progress of a chemical reaction can be monitored by measuring its electrolytic conductivity. It is called conductometry. Conductometric titration is a standard technique of conductometry. This technique is largely used in analytical chemistry.

What is 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.

Terms used in Conductometric Titration 

Various specific terms are used in conductometric titrations which need to be explained before its principle for your better understanding of the topic.

Titrant – A solution used in titration whose concentration is known and is added to another solution of unknown concentration to determine its concentration. 

Analyte – The solution used in titration whose concentration is unknown. 

Equivalence Point – The point in conductometric titration at which conductivity undergoes a sudden change. 

Principle of Conductometric Titration 

Conductometric titration is based on the measurement of conductance of the solution. The conductance of the solution (analyte + titrant) depends on following three factors –

• The number of free ions

• The charge on free ions

• The mobility of the free ions

During titration one of the ions is replaced by the other and these two different ions differ in their ionic conductance as well. So, conductivity of the solution differs during the course of titration. A graph is plotted between change in conductance and volume of titrant added. By this graph an equivalence point can be detected. 

What are the Applications of Conductometric Titration?

Since conductometric titration is exclusively used in analytical chemistry, it has various applications.

Mentioned below are some of its major applications:

1. 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.

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

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

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

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

Conductometric Titration of Strong Acid with a Strong Base 

We are explaining this with HCl a strong acid and NaOH a strong base. We fill NaOH in a burette and HCl is taken in a beaker. A conductivity cell is dipped in it and connected to a conductometer. The Conductometer is connected to the main switch. We switch it on now so that it will start measuring the conductance. In the start of titration conductance is high as a solution in the beaker contains H⁺ ions which have high mobility. As we start adding more base and titration progresses the conductance falls due to the replacement of hydrogen ions which react with OH^- ions of NaOH and forms water. This decreases the conductance. It continues till the equivalence point is reached. At the equivalence point, the solution contains only NaCl. After an equivalence point, the conductance increases due to the presence of OH^- ions in solution. The graph for this titration is given below

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Conductometric Titration of Weak Acid with a Strong Base 

Conductometric titration gives various types of conductometric titration graphs depending on the titrant and analyte used in the titration. When conductometric titration is carried out with weak acid against a strong base then we get a different curve than the above curve. 

We are explaining this with CH₃COOH a weak acid and NaOH a strong base. We fill NaOH in a burette and CH₃COOH is taken in a beaker. In the start of titration conductance is low due to very less ionization of acetic acid. As we start adding more base and titration progresses the conductance increases due to presence of CH₃COO^- and Na⁺. Presence of H⁺ in the solution due to buffer action of sodium acetate and acetic acid. This increase in conductance continues till equivalence point. After the equivalence point, the conductance increases rapidly on adding NaOH due to presence of OH^- ions in solution. The graph for this titration is given below 

What are the Different Types of Conductometric Titration?

Apart from the acid-basic titrations that have been discussed in the above paragraphs, there are many other types of titrations.

Let us take a look at four more types of titrations that have applications across various fields:

1. Precipitation Titration

Precipitation titration is a type of titration in which the titrant is made to react with an analyte to form a precipitate. During this experimentation of titration, an insoluble substance is formed after the analytical procedure is completed and every drop of the analyte is used for the formation of the precipitate. In case the titrant is in excess, it will automatically react with indicators like potassium chromate, silver nitrate or fluorescein ions, and provide a signal to terminate the titration procedure. Basically, the principle on which the precipitation titration method works is that the amount of reagent added should be equal to the amount of the precipitate formed.

It is used in many pharmaceutical industries and food industries to measure the level of the content of salt in different food and drinks.

The precipitation titration is not conducted with just a single method. In fact, there are three types of distinct methods that are used to carry out this titration, namely Volhard’s method, Fagan’s method, and Mohr method.

2. Complexometric Titration

Commonly known as chelatometry, complexometric titration is used to specify an endpoint of a titration through the formation of a colored complex by volumetric analysis. The reason replacement titration is also termed volumetric analysis is that it involves the measurements of volumes of titrants that are reacted. The process involves the tracing of a mixture of metal ions in the solution.

The reaction is brought to equilibrium by adding drops of titrants in the solution in succession. The most common titrant that is used is the EDTA (ethylenediaminetetraacetic acid) titrant. Complexometric titration is one of the most widely used types of titrations because it gives a very accurate identification of the equivalent points. For the most part, this titration is used to titrate phosphates, oxalates, and benzoates.

The commonly used indicators in this titration method are Calmagite and Eriochrome Black T (EBT).  Using these indicators there are two methods by which the endpoint can be detected- the visual method and the instrumental method.

3. Redox Titration

Redox titration is the type of titration which applies the oxidation-reduction reaction. The analyte and the titrate react through this reduction or redox technique. Similar to acid-base titration, the endpoint or the equivalent point in the redox titration is known through the use of an indicator, also called a potentiometer. Redox titration is one of the usual techniques used to determine and identify the concentration of various unknown analytes in a given solution.

Instead of examining the concentration, it is proven to be more convenient to examine the potential of the reaction in redox titration. Hence, it is crucial to obtain the shape of the correlated titration curve. 

Advantages of Conductometric Titration

Conductometric titration techniques are used in various fields due to their various advantages over other titration techniques. A few advantages of conductometric titration are listed below –

• It does not require indicators as titration is based on the conductance of the solution and endpoint or neutralization point is determined graphically. 

• It is suitable for colored solutions as well. 

• As the endpoint is determined graphically, results are more accurate with minimum error.

• It is used for the analysis of turbid suspensions, weak acids, weak bases, a mix of weak and strong acids, etc. 

Limitations of Conductometric Titration

With various advantages, conductometric titration has few limitations as well which are listed below 

• By conductometric titration technique, only a few specific redox titrations can be carried out. 

• It shows less accurate results when the total electrolytic concentration is high in solution. It makes it less satisfactory.

This was brief on conductometric titration and its various titration curves. We have explained two important types of conductometric titration curves here for your understanding. You can get detailed study material on various topics of Chemistry by registering yourself on Vedantu or downloading Vedantu Learning App for classes 6-10, IIT JEE, and NEET.