Learn about the principle of iodometric titration, reaction, indicators, examples, advantages, and how the iodometric titration works.
Titration, often known as titrimetry, is a volumetric analysis used to measure analyte concentration in a sample solution. It consists of a burette filled with titrant and a pipette used to introduce the titrand into the conical flask where the reaction occurs.
A titrant of known concentration is added until the reaction is complete i.e. the chemical equivalence point. A titrant of known concentration is applied, until the reaction is complete, i.e. the chemical equivalence or endpoint. Titration is mainly classified into four types: acid and base, redox, complexometric, and precipitation titration.
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What is redox titration?
Redox titration is a type of titration; it is an oxidation-reduction reaction that occurs between an oxidizing and a reducing agent. There are several types of redox titration, including bromatometry, cerimetry, iodometry, iodimetry, permanganometry, and dichrometry are classified as direct titration, and back titration.
It is a laboratory method used to determine the concentration of a sample analyte by causing a redox reaction between the titrant and the analyte. A potentiometer or a redox indicator may be required for this type of titration.
What is iodometric titration?
Iodometry, known as iodometric titration, is a type of redox titration in which a solute (oxidizing agent) is added to excess iodide to obtain iodine, and the amount of iodine produced is determined by titration with a sodium thiosulfate solution.
It's an indirect titration in which starch indicator is used to determine the endpoint. At the end of the experiment, the blue color of the starch-iodine complex will fade.
What is the principle of iodometric titration?
Iodometric titration works on the principle of determining the concentration of an oxidizing agent in a sample solution. Iodometry involves the indirect titration of iodine liberated by reaction with the analyte.
In which starch solution is used as an indicator as it can absorb the I2 that is released. When titrated with a standardized sodium thiosulphate (Na2S2O3) solution, absorption causes the color to change from bright yellow to dark blue. This indicates the endpoint of the titration.
Reaction involved in iodometric titration:
The reaction between iodine and the thiosulfate ion is as follows.
Examples of iodometric titration:
- To standardize the sodium thiosulfate (Na2S2O3) using potassium dichromate (K2Cr2O7)
- Iodometric estimation of Cu (II) (Copper (II) oxide ) using sodium thiosulfate solution
- Estimation of vitamin C by the iodometric method
How does iodometric titration work?
To use this iodometric titration procedure will require using a material that has oxidizing properties. This oxidizing property indicates that it has the ability to remove electrons that are owned by other compounds.
This oxidizing substance is later dissolved in the solvent and then the solution is acidified. We can use sulfuric acid (H2SO4), hydrochloric acid (HCl), or acetic acid (CH3COOH) to acidify the solution. Following that, add chlorine and allow the mixture to settle in a dark room for a few minutes.
The iodide will then be released as a result of this procedure and then titrated with a standardized solution of sodium thiosulfate (Na2S2O3). As the solution becomes yellow and becomes more dilute, this solution of sodium thiosulfate will act as a reducing agent. The starch indicator will then be added and will be titrated until the color of the solution becomes clear.
Indicator is used in iodometric titration:
In an iodometric titration, starch is commonly used as an indicator since it can absorb the I2 that is released. It causes the absorption color to change from dark blue to pale yellow when the solution is titrated with a standardized thiosulfate solution. Due to the formation of a starch-iodine complex, the endpoint in iodometric titration is the disappearance deep blue-black color.
Advantages of iodometric titration:
- Iodometry can be used to determine the concentration of both reducing and oxidizing agents.
- It has the ability to precisely determine the concentration of the analyte.
- It allows you to visually detect reactivity at equilibrium point(s).
- The presence of iodine in starch causes a visible blue color change that occurs simultaneously, which is one of the two most important criteria for titration.
- It requires only a small amount of chemicals or substances.
Frequently Asked Questions (FAQ):
Why is KI used in iodometric titration?
Because iodide will oxidize iodine in the presence of an oxidizing agent, KI (potassium iodide) is employed in iodometric titrations.
Why excess of KI is used in iodometric titration?
Excess KI is added to help in the solubilization of free iodine, which is insoluble in water under normal conditions.
What do you mean by iodometric and iodimetric titration?
Iodometry and iodimetry both are common volumetric analysis titration methods. Iodometric titration is an indirect titration method used to quantify oxidizing agents, whereas iodometric titration is a direct titration method used to quantify reducing agents.
References:
- Wikipedia contributors. (2022, February 3). Iodometry. In Wikipedia, The Free Encyclopedia. Available Here:
- Hyprowira, and PT Hyprowira Adhitama. Iodometric Titration Functions and How It Works. Available Here:
- ‘Iodometric Determination of Cu in Brass’. Chemistry LibreTexts, 18 Jan. 2017, Available Here:
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