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A redox titration is an analytical technique used to determine the concentration of an unknown substance by reacting it with a precisely known volume of a standard solution in a redox reaction, where electron transfer occurs. It is also called reduction-oxidation titration. Unlike typical acid-base titrations, redox titrations deal with the transfer of electrons between […]
What Is Redox Titration: Get Mastery In 5 Minutes With Case Studies And FAQs
Redox titration (Source: Bing)
A redox titration is an analytical technique used to determine the concentration of an unknown substance by reacting it with a precisely known volume of a standard solution in a redox reaction, where electron transfer occurs.
It is also called reduction-oxidation titration. Unlike typical acid-base titrations, redox titrations deal with the transfer of electrons between reactants, making them particularly useful for analysing substances that undergo electron exchange reactions.
In this article, I will discuss will definition, principle, types, and applications of redox titration. I will also take a look at a case study to better understand how this technique is applied in real-world scenarios.
Major Takeaway: FAQs
What is a redox titration?
A redox titration is an analytical technique used to determine the concentration of an unknown substance by reacting it with a precisely known volume of a standard solution in a redox reaction, where electron transfer occurs.
Why is KMnO4 titration called redox titration?
KMnO₄ titration is called a redox titration because potassium permanganate (KMnO₄) acts as an oxidizing agent, undergoing a reduction process, while the substance being titrated is oxidized, involving electron transfer between the two.
What is Redox Titration?
A redox titration is an analytical procedure in which the amount of an unknown substance is determined by its reaction with a standard solution of known concentration, using a redox reaction. The term redox comes from the combination of two processes:
Reduction: Gain of electrons
Oxidation: Loss of electrons
During the titration, the substance being analysed either gains or loses electrons in response to the titrant (the solution of known concentration) as it undergoes a redox reaction. The point at which the reaction is complete is called the equivalence point, and it can be detected using indicators that signal the end of the titration.
Redox titrations are based on the concept of electron transfer. Here’s how it works:
Oxidising Agent: This is the substance that accepts electrons, causing the other substance to be oxidised.
Reducing Agent: This is the substance that donates electrons, causing the other substance to be reduced.
End Point: The endpoint is usually determined by observing the color change of an indicator or through the use of a potentiometer to measure voltage changes.
In this process, the amount of the reducing or oxidising agent is quantified by how much is required to completely oxidize or reduce the sample. The electrode potential of the substances involved determines the ease with which they can accept or donate electrons.
Types of Redox Titration
There are several types of redox titrations, each suited to different chemical reactions. The most common types include:
Permanganometry:
Uses potassium permanganate (KMnO₄) as the titrant.
Potassium permanganate is a strong oxidizing agent and can be used to titrate reducing agents like iron (II) salts.
The solution turns from purple to colorless as the reducing agent is oxidized.
Involves titrating with iodine (I₂) or a substance that releases iodine.
Typically used to determine the concentration of reducing agents (such as thiosulfates).
Starch is often used as an indicator because it forms a blue complex with iodine.
Dichromatometry:
Uses potassium dichromate (K₂Cr₂O₇) as the titrant, which is a strong oxidizer.
Often used to determine the amount of iron in a sample by titrating with a ferrous solution.
Ferri/ferro Titrations:
Based on the reaction between ferrous (Fe²⁺) and ferric (Fe³⁺) ions.
Ferric ion (Fe³⁺) is reduced to ferrous ion (Fe²⁺) as the reducing agent.
Applications of Redox Titration
Redox titration is widely used in both industrial and laboratory settings. Some of its common applications include:
Determination of Iron Content:
Redox titration can be used to measure the iron content in ores, alloys, and water samples. The reaction typically involves reducing iron (III) to iron (II) using a standard solution of reducing agents like stannous chloride (SnCl₂) or ammonium oxalate.
Redox titration can help in determining the presence of dissolved oxygen (DO) in water, which is an essential parameter for assessing water quality.
It can also detect chlorine levels in water treatment processes, where chlorine acts as an oxidizing agent.
Food Industry:
The technique is used in the food industry to determine the presence of preservatives, antioxidants, and other components that either gain or lose electrons.
Pharmaceuticals:
In the pharmaceutical industry, redox titrations help in the quality control of drugs, particularly those that contain reducing or oxidizing agents, like vitamin C (ascorbic acid).
Titration of Hydrogen Peroxide:
Hydrogen peroxide (H₂O₂) is often analyzed in redox titrations, where potassium permanganate or iodine is used as a titrant.
Case Study:
Example 1: Quantification of Oxalic acid using KMnO4 standard solution
Redox titration
Expert Tip: Potassium permanganate acts as a self-indicator and hence is not any indicator used in this titration
Example 2: Determination of Iron Content in a Sample
Background:
Iron is a vital element found in various ores, and it’s essential in many industrial processes, especially in metallurgy. A common method for determining the iron content in an unknown sample is by using a redox titration.
Procedure:
Preparation:
A sample of the iron ore (which may be impure) is dissolved in hydrochloric acid to convert all the iron to iron (II) ions (Fe²⁺).
The solution is then titrated with a standard solution of potassium permanganate (KMnO₄), which acts as the oxidizing agent.
Reaction: The reaction between iron (II) and potassium permanganate is as follows: 5Fe2++MnO4−+8H+→5Fe3++Mn2++4H2O
As the permanganate solution is added, the iron (II) ions are oxidized to iron (III) ions (Fe³⁺).
The endpoint is reached when a pink color appears, indicating that all the Fe²⁺ has been oxidized.
Calculation:
The amount of potassium permanganate required to reach the endpoint is measured, and from this, the concentration of iron (II) in the original sample can be calculated using stoichiometry.
Results:
This method offers precise results and is commonly used in both academic and industrial laboratories to determine iron content, which is essential for ensuring quality control in various manufacturing processes.
Conclusion
Redox titration is an invaluable tool in analytical chemistry, providing accurate and reliable results for the quantification of substances undergoing electron transfer. Whether you’re determining iron content in ores, testing the quality of water, or measuring the concentration of pharmaceuticals, redox titration is versatile and indispensable. By understanding its principles, types, and applications, we gain insight into how this technique plays a pivotal role in both research and industry.
Next time you’re tasked with determining the concentration of an unknown redox-active substance, you’ll appreciate the power of redox titration in making your analysis precise and efficient.
