Name: redox titration endpoints and indicators
Uploaded: 2024-12-05T18:31:57.000Z
Duration: 1 min 21 s
Channel: JoVE

A redox titration analyzes an oxidation&#8211;reduction reaction that occurs between the analyte and the titrant.
The analyte often must be treated with an auxiliary oxidizing or reducing reagent to uniformly convert the analyte to the single oxidation state required for titration.
The completion of the reaction is detected using a potentiometer or a visual indicator.
The visual indicators are of three types: redox indicators, starch indicators, and self-indicators.
Redox indicators are highly colored dyes exhibiting distinct colors in their oxidized and reduced states.
Most of the redox indicators are sensitive to changes in potential during titration. Plotting the potential against the volume of the titrant generates a titration curve.
The redox titration curves are S-shaped and show a steady rise in potential until a sudden jump is observed near the end point of the titration.
Starch indicators are used in iodine titrations, where starch combines with iodine to form a dark-blue complex.
Self-indicators, which can act as both the titrant and the indicator, can also be used in redox titrations.

redoxtitratie: overzicht

Redox Titration: Overview

Redoxtitratie is een chemische analysetechniek die wordt gebruikt om de concentratie van een onbekende stof te bepalen door de elektronenoverdracht in een redoxreactie (reductie-oxidatie) te meten. Het proces omvat het geleidelijk toevoegen van een titrant met een bekende concentratie van een oxiderend of reducerend middel aan de analyt, de oplossing met een onbekende concentratie, totdat het eindpunt is bereikt, wat aangeeft dat de reactie tussen de twee stoffen is voltooid. Het is cruciaal om ervoor te zorgen dat de analyt zich in een enkele oxidatietoestand bevindt voordat de titratie plaatsvindt. Dit kan worden bereikt door de analyt vooraf te oxideren of vooraf te reduceren met behulp van een hulpreagens. Redoxtitraties gebruiken verschillende soorten redoxindicatoren om het eindpunt te bepalen, waaronder kleurveranderende kleurstoffen en potentiometrische methoden met behulp van elektroden. Visuele redoxindicatoren veranderen van kleur op basis van hun oxidatietoestand, wat aangeeft dat een bepaald redoxpotentieel is bereikt. Potentiometrische methoden meten daarentegen de verandering in elektrisch potentieel over de oplossing met behulp van een pH- of redoxelektrode om het eindpunt te bepalen. Zelfindicatoren zijn stoffen die een kleurverandering vertonen vanwege hun inherente redoxeigenschappen, waardoor externe indicatoren niet meer nodig zijn. Zetmeel is een veelgebruikte visuele indicator bij jodometrische titraties en vormt een donkerblauw complex wanneer het reageert met jodium. De keuze van de indicator bij een redoxtitratie hangt af van de specifieke reactie en de gewenste gevoeligheid en nauwkeurigheid van de analyse. Een titratiecurve wordt gemaakt door de verandering in potentiaal of de concentratie van de analyt uit te zetten tegen het volume van de toegevoegde titrant.

Redoxtitratie: overzicht

Redox titration is a chemical analysis technique used to determine the concentration of an unknown substance by measuring the electron transfer in a redox ...

Education

JoVE Core

Analytical Chemistry

Analytische chemie

Unit 1

Electrochemical Analyses and Redox Titration

Elektrochemische analyses en redox-titratie

electrochemical-analyses-and-redox-titration

KEY TERMS AND CONCEPTS

KERNTERMEN EN CONCEPTEN

redox titration endpoints and indicators

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 reagent. This step helps the titration start from a clear chemical state.

Endpoints in redox titration can be detected with visual indicators or with potentiometric methods. Visual redox indicators change color as their oxidation state changes, which signals that the solution has reached a certain redox potential. Potentiometric methods track the change in electrical potential across the solution using a pH or redox electrode.

Some substances act as self-indicators because their own redox behavior causes a visible color change. In iodometric titrations, starch is a common visual indicator. It forms a dark blue complex when it reacts with iodine.

The best indicator depends on the reaction and on how sensitive and accurate the measurement needs to be. A titration curve is then made by plotting the change in potential or analyte concentration against the volume of titrant added. This curve helps show how the reaction progresses during the analysis.

Redox Titration Endpoints and Indicators

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: overview

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

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...

redox titration: other oxidizing and reducing agents

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,...

potentiometric titration: overview

Endpoint Detection in Potentiometric Titration

Potentiometric titration is a quantitative analytical method used to find the concentration of an analyte by measuring the potential difference between two electrodes in a solution. The endpoint is the point where this potential changes sharply. It usually appears when the stoichiometric reaction between the analyte and the titrant is complete. To find the endpoint, the measured potential difference is plotted against the volume of titrant added. This graph is called a titration curve. A...

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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-coulometric-titration

Electrically Generated Reagents in Titration

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Voltammetry for Detecting Redox Species

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Voltammetry and Faradaic Current

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Voltammogram Shapes and Redox Analysis

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voltammetric-techniques-cyclic-voltammetry

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key terms and concepts

Learn how redox titration uses titrant, oxidation states, and indicators to find an unknown concentration. Includes endpoints, electrodes, and starch.

Redox Titration Endpoints and Indicators | JoVE K12

analytical chemistry

JoVE Core Analytical Chemistry simplifies complex chemical principles by breaking them down into clear, engaging animations, making topics from SI Units to NMR spectroscopy more accessible and straightforward. Additionally, the scientist-in-action videos highlight the application of these concepts in real-world research conducted in laboratories globally.

Redox Titration Endpoints and Indicators

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