Name: choosing oxidizing titrants in redox titration
Uploaded: 2024-12-05T18:31:57.000Z
Duration: 1 min 26 s
Channel: JoVE

Neben Jod können mehrere andere Oxidations- oder Reduktionsmittel als Titrantien bei Redox-Titrationen eingesetzt werden.
Kaliumpermanganat ist ein stark oxidierendes Titriermittel, das in einer stark sauren Lösung von Mangan(VII) zu Mangan(II) reduziert wird.
Hier fungiert das violette Permanganat als Selbstindikator, da Mangan(II) farblos ist.
Reduzierende Analyten können auch mit sauren Cer(IV)-Lösungen titriert werden, während Redoxindikatoren für die Endpunktdetektion verwendet werden. Bei der Titration wird der Analyt oxidiert, während Cer(IV) zu Cer(III) reduziert wird.
Kaliumdichromat ist ein mäßig starkes oxidierendes Titriermittel, das in sauren Lösungen von Chrom(VI) zu Chrom(III) reduziert wird. Der Dichromat-Endpunkt wird mit Hilfe eines Redox-Indikators beobachtet.
Im Gegensatz dazu werden die meisten reduzierenden Titriermittel durch Luftsauerstoff oxidiert, so dass sie selten für die direkte Titration oxidierender Analyten verwendet werden.
Zum Beispiel wird Thiosulfat indirekt als typisches Reduktionstitriermittel für iodometrische Titrationen verwendet.
Eine angesäuerte Eisen(II)-Lösung kann jedoch verwendet werden, um einige stark oxidierende Analyten wie Cer(IV), Chrom(VI) und Vanadium(V) zu titrieren.

redoxtitration: andere oxidations- und reduktionsmittel

Redox Titration: Other Oxidizing and Reducing Agents

Neben Jod können auch andere Oxidations- oder Reduktionsmittel als Titrationsmittel bei Redoxtitrationen dienen. Übliche Oxidations-Titrationsmittel sind KMnO_4, Cer(IV) und K_2Cr_2O_7. Die Wahl der Oxidations-Titrationsmittel hängt von Faktoren wie Stabilität, Kosten, Analytstärke und Reaktionsgeschwindigkeit zwischen Analyt und Titrationsmittel ab. KMnO_4 ist ein stark oxidierendes Titrationsmittel, das in einer stark sauren Lösung von Mn(VII) zu Mn(II) reduziert wird und gleichzeitig den Analyten in einen höheren Oxidationszustand oxidiert. In diesem Fall fungiert KMnO_4 als Selbstindikator und wird nach Abschluss der Reaktion farblos.

Reduzierende Analyten können auch mit sauren Cer(IV)-Lösungen titriert werden, wobei zur Endpunkterkennung Redoxindikatoren eingesetzt werden. Der Analyt wird während der Titration oxidiert, während Ce(IV) zu Ce(III) reduziert wird. Kaliumdichromat (K_2Cr_2O_7), ein mäßig stark oxidierendes Titrationsmittel, wird in sauren Lösungen zu Cr^3+ reduziert. Der Dichromat-Endpunkt wird mithilfe eines Redoxindikators beobachtet.

Im Gegensatz dazu werden die meisten reduzierenden Titrationsmittel durch atmosphärischen Sauerstoff oxidiert, was sie für die direkte Titration oxidierender Analyten ungeeignet macht. Beispielsweise wird Thiosulfat indirekt als typisches reduzierendes Titrationsmittel für iodometrische Titrationen eingesetzt. Eine angesäuerte Eisen(II)-Lösung kann jedoch zur Titration einiger stark oxidierender Analyten wie Cer(IV), Chrom(VI) und Vanadium(V) verwendet werden.

Redoxtitration: Andere Oxidations- und Reduktionsmittel

Neben Jod können auch andere Oxidations- oder Reduktionsmittel als Titrantien bei Redoxtitrationen dienen. Zu den gängigen oxidierenden Titrantien gehören KMnO4, Cer(IV) und ...

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

Education

Lehre

JoVE Core

Analytical Chemistry

Analytische Chemie

Unit 1

Einheit 1

Electrochemical Analyses and Redox Titration

Elektrochemische Analysen und Redoxtitration

electrochemical-analyses-and-redox-titration

KEY TERMS AND CONCEPTS

ZENTRALE BEGRIFFE UND KONZEPTE

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, so the solution turns colorless when the reaction is complete.

Cerium(IV) solutions can titrate reducing analytes in acidic conditions. During the reaction, the analyte is oxidized and Ce(IV) is reduced to Ce(III). A redox indicator is used to detect the endpoint.

Potassium dichromate is a moderately strong oxidizing titrant. In acidic solution, dichromate reduces to Cr3+, and a redox indicator is again used to spot the endpoint. Most reducing titrants are oxidized by atmospheric oxygen, so they are not suitable for direct titration of oxidizing analytes.

Thiosulfate is a common reducing titrant used indirectly in iodometric titrations. An acidified iron(II) solution can also titrate some strong oxidizing analytes, including cerium(IV), chromium(VI), and vanadium(V).

Choosing Oxidizing Titrants in Redox Titration

choosing-oxidizing-titrants-in-redox-titration

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...

electrodes: overview

Types of Electrodes in Electrochemistry

Electrodes are conductive materials in an electrochemical cell. They allow electron transfer reactions to happen at their surfaces. Electrochemical measurements use them to control and measure current and potential. The working electrode, also called the indicator electrode, is the main sensing electrode. Its potential changes with the analyte concentration and with the activity of the electroactive species. Common indicator electrodes include inert platinum electrodes, silver electrodes that...

interfacial electrochemical methods: overview

interfacial-electrochemical-methods-overview

Static and Dynamic Electrochemical Methods

Static and dynamic electrochemical methods study what happens at the boundary between an electrode and a solution. These interfacial methods focus on the electrode-solution interface rather than the overall properties of the liquid. They are useful in electroanalytical chemistry because they can detect very small changes in analyte concentration. These methods are grouped by whether a nonzero current flows through the cell. Static methods, such as potentiometry, measure the cell potential...

potentiometry: overview

Potentiometry and Electrochemical Cell Potential

Potentiometry measures the potential difference between two electrodes in an electrochemical cell. It does this without drawing significant current, so the solution’s composition is not altered. The method uses an indicator electrode, which exchanges electrons with the analyte solution, and a reference electrode, which keeps a constant potential. Each electrode is placed in a solution that makes up a half-cell. In a common setup, the reference electrode is the anode, or left-hand electrode,...

potentiometry: types of electrodes

Reference and Indicator Electrodes in Potentiometry

Potentiometric measurements use reference electrodes and indicator electrodes to track changes in a solution. A reference electrode gives a stable baseline, while indicator and working electrodes respond to changes in the solution’s composition. The Standard Hydrogen Electrode, or SHE, is a common reference electrode. It keeps a zero potential at all temperatures. However, it needs a continuous supply of hydrogen gas, so it is not practical for routine use. The Saturated Calomel Electrode, or...

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Membrane Electrodes in Ion Sensing

Membrane electrodes measure ions by using a selective membrane that creates a potential difference across it. This membrane potential is called the asymmetry potential, and it can remain nonzero even when analyte concentrations are the same on both sides of the membrane. The signal usually depends on all ions in the sample that can interact with the membrane, not just one analyte. Selectivity is described by a selectivity coefficient. This value compares the response to an interferent with the...

redox titration: overview

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...

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 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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Gran Plot for Titration Endpoint Prediction

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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Electrode Weighing in Electrogravimetric Analysis

Electrogravimetric analysis measures an analyte by weighing the material that deposits on an electrode. A pre-weighed working electrode is placed in solution, and a potential is applied. The target substance then deposits by reduction at the cathode or by oxidation at the anode. After electrolysis, the electrode is weighed again. The mass increase gives the weight of the analyte in the solution. To check that deposition is complete, the fresh electrode surface is exposed to the solution while...

coulometry: overview

Coulometry and Electrical Charge Analysis

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Measuring Analyte Charge by Potentiostatic Coulometry

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controlled-current coulometry: overview

Controlled-Current Coulometry in Redox Analysis

Controlled current coulometry is an electrochemical method used to measure the amount of a substance by passing a steady current through a cell. It is also called amperostatic coulometry. The analyte, or substance being analyzed, reacts at the electrode surface as charge moves through the system. The amount of analyte is found by measuring how long it takes for a known charge to pass. This calculation follows Faraday’s laws of electrolysis. A typical setup includes a galvanostat, a...

controlled-current coulometry: coulometric titration

controlled-current-coulometry-coulometric-titration

Electrically Generated Reagents in Titration

Coulometric titrations use an electrically generated reagent to measure the amount of a substance in a sample. The electron acts as the standard reagent, and the result depends on the current and the time used to generate it. The method follows the same basic idea as a regular titration, including endpoint detection. Two conditions are essential for this type of titration. First, the electrode reaction that makes the reagent must be 100% efficient. Second, the generated reagent must react...

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Voltammetry for Detecting Redox Species

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voltammetry: factors affecting measurements

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Voltammetry and Faradaic Current

Voltammetry measures faradaic current, which is the current created by redox reactions of an analyte at the working and auxiliary electrodes. The current from reduction is called cathodic current and carries a positive charge. The current from oxidation is called anodic current and has a negative charge. The applied potential at the working electrode controls the flow of faradaic current. The size of that current depends on how fast the oxidation or reduction reaction occurs at the electrode...

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Voltammogram Shapes and Redox Analysis

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Polarography and Voltammetry with Mercury Drops

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Pulse Voltage Methods for Electrochemistry

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amperometry: overview

Measuring Analytes with Amperometric Sensors

Amperometry measures specific analytes in a solution by tracking the electric current from an electrochemical reaction. A constant potential is applied between a working electrode and a reference electrode. The current that results is proportional to the analyte concentration. The Clark oxygen electrode is a common example of amperometry. It uses a cathode and an anode sealed inside a gas-permeable membrane. The cathode is typically platinum or gold, and the anode is silver. When a potential...

key terms and concepts

Explore how KMnO4, cerium(IV), and dichromate are used in redox titrations, how endpoints are detected, and why some reducing titrants are used indirectly.

Choosing Oxidizing Titrants in Redox Titration | JoVE K12

analytical chemistry

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Choosing Oxidizing Titrants in Redox Titration

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