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.
“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.
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.
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.
We are explaining this with HCl a strong acid and NaOH a strong base. We fill NaOH in 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 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 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 equivalence point, the conductance increases due to presence of OH- ions in solution. The graph for this titration is given below – Image will be uploaded soon.
Conductometric titration gives various types of conductometric titration graphs depending on 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 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 –
Conductometric titration techniques are used in various fields due to its various advantages over other titration techniques. Few advantages of conductometric titration are listed below –
It does not require indicators as titration is based on conductance of the solution and end point or neutralization point is determined graphically.
It is suitable for colored solutions as well.
As the end point is determined graphically, results are more accurate with minimum error.
It is used for analysis of turbid suspensions, weak acids, weak bases, mix of weak and strong acids etc.
With various advantages, conductometric titration has few limitations as well which are listed below –
By conductometric titration technique, only 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 a 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 class 6-10, IIT JEE and NEET.