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

A iodometria e a iodemetria são métodos titulométricos utilizados para analisar a quantidade de agentes oxidantes ou redutores presentes em uma amostra, respectivamente.
Em titulações iodométricas, a solução de analito oxidante é tipicamente acidificada e tratada com um excesso de íons iodeto, produzindo uma quantidade equivalente de iodo em equilíbrio com o triiodeto. O iodo liberado é então titulado contra um agente redutor padronizado.
Uma solução de amido recém-preparada é adicionada perto do ponto final, formando um complexo de amido-iodo azul intensamente escuro. A titulação continua até que a cor azul desapareça.
A relação estequiométrica via iodo entre o analito oxidante e o titulante redutor permite a determinação da concentração do analito.
Em contraste, as titulações iodimétricas envolvem a titulação direta de um analito redutor na presença de amido contra uma solução padrão de iodo até que a solução fique azul escura, mostrando que todo o analito está oxidado e o complexo amido-iodo está se formando.
Conhecendo a estequiometria da reação e o volume de titulante consumido, a concentração do analito pode ser determinada.

titulação redox: iodometria e iodimetria

Redox Titration: Iodimetry and Iodometry

Iodometria e iodimetria são métodos analíticos usados ​​para determinar a concentração de agentes oxidantes ou redutores usando iodo. Em titulações iodométricas, a solução do analito oxidante é geralmente acidificada e tratada com um excesso de íons iodeto, o que gera uma quantidade equivalente de iodo em equilíbrio com triiodeto. O iodo liberado é subsequentemente titulado diretamente contra um agente redutor padronizado. À medida que a cor do iodo diluído se torna amarelo-claro, algumas gotas de solução de amido recém-preparada são adicionadas, criando um complexo azul-escuro intenso de amido-iodo. A titulação prossegue até o desaparecimento da cor azul, permitindo a determinação da concentração do analito por meio da relação estequiométrica entre iodo, o analito oxidante e o titulante redutor. A titulação deve ser realizada de forma rápida e com agitação vigorosa para obter resultados precisos.

Em titulações iodimétricas, um analito redutor é titulado diretamente contra uma solução padrão de iodo na presença de amido. O amido atua como um indicador, formando um complexo amido-iodo azul escuro enquanto o iodo está em excesso. Conforme a titulação progride, o analito redutor reage com o iodo, fazendo com que a concentração de iodo diminua. Quando todo o analito redutor tiver reagido e estiver completamente oxidado, qualquer iodo adicional adicionado não será reduzido, resultando na formação do complexo amido-iodo azul escuro. Essa mudança de cor significa o ponto final da titulação.

Para determinar a concentração do analito, a estequiometria da reação (representada pela equação química balanceada) e o volume da solução padrão de iodo usada durante a titulação são considerados. Sabendo a quantidade de iodo que reagiu com o analito e a relação estequiométrica entre o iodo e o analito, a concentração do analito redutor na amostra original pode ser determinada com precisão.

Titulação Redox: Iodometria e Iodimetria

A iodometria e a iodemetria são métodos analíticos usados para determinar a concentração de agentes oxidantes ou redutores usando iodo. Em titulações iodométricas, ...

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JoVE Core

Analytical Chemistry

Química Analítica

Unit 1

Unidade 1

Electrochemical Analyses and Redox Titration

Análises Eletroquímicas e Titulação Redox

electrochemical-analyses-and-redox-titration

KEY TERMS AND CONCEPTS

TERMOS E CONCEITOS-CHAVE

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

Electrochemistry connects electrical measurements with chemical reactions, especially oxidation and reduction. It focuses on how electron movement helps explain reaction behavior. Oxidation is the loss of electrons from a substance, and reduction is the gain of electrons. A species with strong electron affinity is an oxidizing agent, or oxidant. A species that donates electrons is a reducing agent, or reductant. These redox steps are often described with half-reactions. When electrons move...

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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...

redox titration: iodimetry and iodometry

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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redox-titration-other-oxidizing-and-reducing-agents

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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Controlled-Current Coulometry in Redox Analysis

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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

analytical chemistry

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Using Iodine to Find Unknown Concentrations

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