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

La yodometría y la yodometría son métodos de titulación utilizados para analizar la cantidad de agentes oxidantes o reductores presentes en una muestra, respectivamente.
En las valoraciones yodométricas, la solución de analito oxidante se acidifica y se trata con un exceso de iones de yoduro, produciendo una cantidad equivalente de yodo en equilibrio con el triyoduro. A continuación, el yodo liberado se valora frente a un agente reductor estandarizado.
Se agrega una solución de almidón recién preparada cerca del punto final, formando un complejo de almidón y yodo de color azul oscuro intenso. A continuación, la valoración continúa hasta que desaparece el color azul.
La relación estequiométrica a través del yodo entre el analito oxidante y el valorante reductor permite determinar la concentración del analito.
Por el contrario, las valoraciones yodimétricas implican la valoración directa de un analito reductor en presencia de almidón frente a una solución estándar de yodo hasta que la solución se vuelve azul oscuro, lo que demuestra que todo el analito está oxidado y se está formando el complejo almidón-yodo.
Conociendo la estequiometría de reacción y el volumen de valorante consumido, se puede determinar la concentración del analito.

titulación redox: yodometría y yodimetría

Redox Titration: Iodimetry and Iodometry

La yodometría y la yodimetría son métodos analíticos que se utilizan para determinar la concentración de agentes oxidantes o reductores utilizando yodo. En las titulaciones yodométricas, la solución de analito oxidante suele acidificarse y tratarse con un exceso de iones de yoduro, lo que genera una cantidad equivalente de yodo en equilibrio con el triyoduro. El yodo liberado se titula posteriormente directamente frente a un agente reductor estandarizado. A medida que el color del yodo diluido se vuelve amarillo pálido, se añaden unas gotas de solución de almidón recién preparada, lo que crea un complejo de almidón y yodo de color azul oscuro intenso. La titulación continúa hasta la desaparición del color azul, lo que permite la determinación de la concentración del analito a través de la relación estequiométrica entre el yodo, el analito oxidante y el titulante reductor. La titulación debe realizarse rápidamente y agitando vigorosamente para obtener resultados precisos.
En las titulaciones yodimétricas, un analito reductor se titula directamente contra una solución estándar de yodo en presencia de almidón. El almidón actúa como un indicador, formando un complejo de almidón-yodo de color azul oscuro cuando el yodo está en exceso. A medida que avanza la titulación, el analito reductor reacciona con el yodo, lo que hace que la concentración de yodo disminuya. Cuando todo el analito reductor ha reaccionado y se oxida por completo, cualquier yodo adicional agregado no se reducirá, lo que da como resultado la formación del complejo de almidón-yodo de color azul oscuro. Este cambio de color significa el punto final de la titulación.
Para determinar la concentración del analito, se consideran la estequiometría de la reacción (representada por la ecuación química balanceada) y el volumen de la solución estándar de yodo utilizada durante la titulación. Al conocer la cantidad de yodo que reaccionó con el analito y la relación estequiométrica entre el yodo y el analito, se puede determinar con precisión la concentración del analito reductor en la muestra original.

Titulación Redox: Yodometría y yodimetría

La yodometría y la yodometría son métodos analíticos utilizados para determinar la concentración de agentes oxidantes o reductores utilizando yodo. En las valoraciones yodométricas, ...

Education

Educación

JoVE Core

Analytical Chemistry

Química Analítica

Unit 1

Unidad 1

Electrochemical Analyses and Redox Titration

Análisis electroquímicos y valoración redox

electrochemical-analyses-and-redox-titration

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

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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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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A Gran plot helps predict the endpoint of a potentiometric or acid-base titration before the endpoint is reached. It uses titration data collected only up to a point that is still below the equivalence volume. The data are then transformed into a straight-line format. To build the plot, the line is extended to the x-axis. That x-intercept shows the titrant volume needed to reach the equivalence point. In potentiometric titration, the Gran plot uses the volume-corrected base-10 antilogarithm of...

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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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