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Conductometric Titration is a process where the reaction mixture’s electrolytic conductivity is continuously observed as one reactant is added through a burette. It is used to determine the concentration of the chemical substance that is to be measured (also called analyte). Conductometry determines the overall conductance of any solution or analyzes the endpoint of titrations which include ions.
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Key Terms: Conductometric Titration, Conductometry, Conductometer, Titration, Conductance, Acid, Base, Conductivity, Ions
What is Conductometric Titration?
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Conductometric Titration is the method that involves the regular addition of a reactant to the reaction mixture. In this mixture, corresponding changes in its electrolytic conductivity are observed and documented. When acids are reacted with a standard base solution, we can determine the acid’s strength.
- An increase or decrease in the electrolytic conductivity of the reaction mixture is related to the change in the concentration of hydrogen and hydroxyl ions.
- Sudden change in the electrolytic conductivity can lead to the inference that a stoichiometric point has been reached.
The conductometric titration graph is shown below:
Conductometric Titration Graph
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The conductometric titration principle works on the fact that during titration one of the ions is replaced by another, leading to a difference in the conductivity of both ions. This results in a variation of conductivity of the given solution throughout the titration through the principle of conductometry. An equivalent point is determined by using a graph of Conductance vs Volume of titrant (solution in burette).
| Constant Conductivity is determined by the formula: Gt = Gt cal { 1 + a (t - t cal) } Where,
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Conductometric Titration Theory
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Conductometric Titration Theory takes place when a neutralization reaction occurs between an acid and a base. Here, the conductivity of the solution is lowered due to the addition of base initially.
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 observe two straight lines with opposite slopes. The point at which these two lines meet is called the equivalence point.
Conductometric Titration Theory Graph
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Working of Conductometric Titration
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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.
Conductometric Titration Process
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Observations of Conductometric Titration
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Advantages and Disadvantages of Conductometric Titration
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The advantages and disadvantages of conductometry are as follows:
Advantages of Conductometric Titration
Disadvantages of Conductometric Titration
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Conductometric Titration Applications
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Conductometric titration applications in analytical chemistry are as below:
- They are used to determine the purity of water by checking the pollution levels of various water bodies.
- Conductometric titration is also used to examine the alkalinity of freshwater bodies and the salinity of seawater.
- Conductometry is also used in the food industry by microbiologists in order to trace microorganisms.
- The application of conductometric titration is also found in the pharmaceutical industry. It is used to check the basicity of organic acids and to detect antibiotics.
- It is used to determine the purity of distilled water or its freshness by examining the chemical equilibrium in ionic reactions.
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Things to Remember
- 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.
Sample Questions
Ques. What is the main objective or working principle of conductometric titration? (1 mark)
Ans. The working principle of conductometric titration is to measure the conductivity of the solution.
Ques. What is the unit of conductometry? (2 marks)
Ans. Conductometry basically measures the electrical conductivity of a given solution. Conductance can be understood as the flow of current through the conductor. Simply, we can say that it is the reciprocal of resistance. Therefore, the unit for the conductance is Seimens (S). Siemens is the reciprocal of Ohms (Ω−1).
Ques. Why conductometric titration is used? (5 marks)
Ans. Conductometric Titration is widely used in analytical chemistry to measure the conductance of a mixture. Herein, the mixture’s electrical conductivity is constantly measured as a reactant is added. The other uses or applications of conductometry are:
- To check the purity of water.
- To trace microorganisms.
- To check the levels of basicity in organic acids.
- To determine the salinity of seawater.
Ques. What is the Principle of Conductometric Titrations? (3 marks)
Ans. The principle of the working of Conductometric Titrations is that the electrolytic conductivity of any solution is affected by the replacement of an ion with another, with respect to the differences in the ionic conductivities. For instance, the H+ ion’s conductivity is greater than that of a Na+ ion. This is due to the dependence of an ion’s conductivity on its mobility. Now, as the H+ ion is comparatively smaller in size than Na+, the ion moves through the solution at a faster speed.
Ques. What are the different types of conductometric titration? (5 marks)
Ans. The various types of conductometric titration are:
- Acid- base or neutralisation titrations:
- Replacement or displacement titrations
- Redox titrations
- Precipitation Titration
- Complexometric titrations
- Non-aqueous titrations
Ques. Why does the Conductivity of the solution rise quickly after the Equivalence Point? (2 marks)
Ans. After the equivalence point of a conductometric titration process is reached, the further addition of the titrant creates an excess of ions which leads to increased conductivity of the solution. For instance, when we add NaOH to a solution of HCl, the concentration of the hydroxyl ions (OH–) increases after the endpoint is reached, thereby the conductivity of the solution increases.
Ques. State the disadvantages of Conductometric titration. (2 marks)
Ans. 1. Only a few redox titrations can be carried out through conductometric titration.
- When the solution has a high total electrolytic concentration, it shows less accurate results.
Ques. Why indicator is not used in conductometric titration? (2 marks)
Ans. In this titration, as we are using a conductometer to measure the conductance, therefore no indicator is required to measure the increase or decrease of ions. The change is observed and measured by the conductometer itself.
Ques. In the titration K2Cr2O7 and FeSO4, the following data is obtained, V1mL of M1K2Cr2O7 requires V2mL of M2FeSO4. Which of the following relations is true for the above titration? (5 marks)
A) 6M1V1=M2V2
B) M1V1=6M2V2
C) M1V1=M2V2
D) 3M1V1=4M2V2
Ans. This is an oxidation-reduction titration as Potassium dichromate (K2Cr2O7) is an oxidizing agent and oxidized Iron(II) sulphate (FeSO4) to Iron(III) sulphate {Fe2(SO4)3} in the presence of sulphuric acid (H2SO4) in an aqueous medium in which ions can move and react freely.
A balanced chemical equation for the reaction would be:
K2Cr2O7 + 7H2SO4 + 6FeSO4→K2SO4 + Cr2(SO4)3 + 3Fe2(SO4)3 + 7H2O
From coefficients of substances, it is evident that for every one mole of Potassium dichromate, six moles of Iron (II) sulphate are used.
To find number of moles of Potassium dichromate (K2Cr2O7) = concentration × volume = M1V1 ---------(i)
To find the number of moles of Iron (II) sulphate (FeSO4) = concentration × volume = M2V2 ---------(ii)
From the balanced chemical equation:
\(\frac{Number of Moles of K_2Cr_2O_7}{Number of Moles of FeSO_4} = \frac{1}{6}\)
Number of moles of Iron (II) sulphate (FeSO4) = 6 x Number of moles of Potassium dichromate = M2V2=6M1V1
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