Name: using iodine to find unknown concentrations
Uploaded: 2024-12-05T18:31:57.000Z
Duration: 1 min 23 s
Channel: JoVE

Iodometry and iodimetry are titrimetric methods used to analyze the amount of oxidizing or reducing agents present in a sample, respectively.
In iodometric titrations, the oxidizing analyte solution is typically acidified and treated with an excess of iodide ions, producing an equivalent amount of iodine in equilibrium with triiodide. The liberated iodine is then titrated against a standardized reducing agent.
A freshly prepared starch solution is added near the endpoint, forming an intensely dark blue starch&#8211;iodine complex. The titration then continues until the blue color disappears.
The stoichiometric relationship via iodine between the oxidizing analyte and reducing titrant enables the determination of the concentration of the analyte.
In contrast, iodimetric titrations involve direct titration of a reducing analyte in the presence of starch against a standard iodine solution until the solution turns dark blue, showing that all the analyte is oxidized and the starch&#8211;iodine complex is forming.
Knowing the reaction stoichiometry and volume of titrant consumed, the concentration of the analyte can be determined.

redox titration: iodimetry and iodometry

Redox Titration: Iodimetry and Iodometry

Iodometry and iodimetry are analytical methods used to determine the concentration of oxidizing or reducing agents using iodine. In iodometric titrations, the oxidizing analyte solution is usually acidified and treated with an excess of iodide ions, which generates an equivalent amount of iodine in equilibrium with triiodide. The released iodine is subsequently titrated directly against a standardized reducing agent. As the dilute iodine color becomes pale yellow, a few drops of freshly prepared starch solution are added, creating an intense dark blue starch&#8211;iodine complex. The titration is continued until the disappearance of the blue color, allowing the determination of the analyte&#39;s concentration through the stoichiometric relationship between iodine, the oxidizing analyte, and the reducing titrant. The titration should be performed quickly and vigorously stirring for accurate results.
In iodimetric titrations, a reducing analyte is titrated directly against a standard iodine solution in the presence of starch. The starch acts as an indicator, forming a dark blue starch&#8211;iodine complex when the iodine is in excess. As the titration progresses, the reducing analyte reacts with the iodine, causing the iodine concentration to decrease. When all the reducing analyte has reacted and is completely oxidized, any additional iodine added will not be reduced, resulting in the formation of the dark blue starch&#8211;iodine complex. This color change signifies the endpoint of the titration.
To determine the concentration of the analyte, the stoichiometry of the reaction (represented by the balanced chemical equation) and the volume of the standard iodine solution used during the titration are considered. By knowing the amount of iodine that reacted with the analyte and the stoichiometric relationship between the iodine and the analyte, the concentration of the reducing analyte in the original sample can be accurately determined.

Iodometry and iodimetry are analytical methods used to determine the concentration of oxidizing or reducing agents using iodine. In iodometric titrations, ...

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Analytical Chemistry

Unit 1

Electrochemical Analyses and Redox Titration

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KEY TERMS AND CONCEPTS

using iodine to find unknown concentrations

Iodometry and iodimetry use iodine to measure unknown concentrations in redox titrations. These methods help determine the amount of an oxidizing or reducing agent in a sample. The key idea is that iodine changes color and reacts in a known stoichiometric ratio with the analyte.

In iodometric titrations, the sample usually contains an oxidizing agent. The solution is acidified and then treated with an excess of iodide ions, which releases an equivalent amount of iodine in equilibrium with triiodide. The iodine is then titrated against a standardized reducing agent.

As the iodine solution becomes pale yellow, a few drops of freshly prepared starch solution are added. Starch forms a dark blue starch-iodine complex. The titration continues until the blue color disappears. The sample should be stirred vigorously and the titration should be done quickly for accurate results.

In iodimetric titrations, the process is reversed. A reducing analyte is titrated directly with a standard iodine solution in the presence of starch. As the reducing analyte reacts with iodine, the iodine level drops. When all of the reducing analyte has reacted, extra iodine remains and the dark blue starch-iodine complex appears. That color change marks the endpoint.

For both methods, the concentration of the analyte is calculated from the balanced chemical equation and the volume of iodine solution or titrant used. The stoichiometric relationship between iodine and the analyte shows how much of the sample reacted. This makes iodometry and iodimetry useful analytical tools for measuring unknown redox concentrations.

Using Iodine to Find Unknown Concentrations

using-iodine-to-find-unknown-concentrations

electrochemistry: overview

Electrochemistry and Redox Reactions

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Redox titration uses electron transfer in a redox, or reduction-oxidation, reaction to find the concentration of an unknown solution. The titrant has a known concentration, and it is added gradually to the analyte, which is the solution being tested. The endpoint shows when the reaction between the two substances is complete. Before a redox titration begins, the analyte should be in a single oxidation state. If needed, this is done by pre-oxidizing or pre-reducing the sample with an auxiliary...

Iodometry and iodimetry use iodine to measure unknown concentrations in redox titrations. These methods help determine the amount of an oxidizing or reducing agent in a sample. The key idea is that iodine changes color and reacts in a known stoichiometric ratio with the analyte. In iodometric titrations, the sample usually contains an oxidizing agent. The solution is acidified and then treated with an excess of iodide ions, which releases an equivalent amount of iodine in equilibrium with...

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Choosing Oxidizing Titrants in Redox Titration

Redox titrations can use oxidizing titrants other than iodine. Common choices include potassium permanganate (KMnO4), cerium(IV), and potassium dichromate (K2Cr2O7). The best titrant depends on stability, cost, analyte strength, and the reaction rate between the analyte and the titrant. Potassium permanganate is a strong oxidizing titrant in highly acidic solution. It reduces from Mn(VII) to Mn(II) while it oxidizes the analyte to a higher oxidation state. KMnO4 also works as a self-indicator,...

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Endpoint Detection in Potentiometric Titration

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key terms and concepts

Learn how iodometry and iodimetry use iodine, iodide, and starch to measure unknown oxidizing or reducing agents in redox titrations.

Using Iodine to Find Unknown Concentrations | JoVE K12

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Using Iodine to Find Unknown Concentrations

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