Today, we shall take a look at the Tests for Oxidising Agents and Reducing Agents using common chemical reagents in our school laboratories.

Before we can continue, is important to first understand what is a Redox Reaction and how to identify one.

You will also need to know the definitions of Oxidising Agents and Reducing Agents.

A reducing agent is a substance that reduces another substance by:

• giving hydrogen to the substance
• removing oxygen from the substance
• giving electrons to the substance

In the process of reducing another substance, the reducing agent itself becomes oxidised.

Common Reducing Agents are:

• Potassium iodide, KI (colourless solution)
• Reactive metals such as Mg, Zn
• Hydrogen gas, H₂
• Carbon, C
• Carbon monoxide, CO
• Hydrogen sulfide, H₂S
• Sulfur dioxide, SO₂
• etc

while

An oxidising agent is a substance that oxidises another substance by

• giving oxygen to the substance
• removing hydrogen from the substance
• receiving electrons to the substance

In the process of oxidising another substance, the oxidising agent itself becomes reduced. I have blogged about these agents before using the analogy of a property and an insurance agents.

Common Oxidising Agents are:

• Acidified potassium manganate (VII), KMnO₄ (purple solution)
• Acidified potassium dichromate (VI), K₂Cr₂O₇ (orange solution)
• Halogens e.g. Cl₂, Br₂
• Concentrated sulfuric acid, H₂SO₄
• Nitric acid, HNO₃
• Oxygen, O₂
• etc

In the video below, i will share with you on the step-by-step strategy to test for Oxidising and Reducing Agents using common laboratory reagents such as aqueous potassium iodide, KI(aq) and acidified potassium manganate (VII), KMnO₄(aq) solutions.

Test for Oxidising Agent:

Use of a Reducing Agent e.g. aqueous potassium iodide, KI(aq)

Observation: Colourless solution turns brown

Chemistry behind it: 2I^–(aq) => I₂(aq) + 2e^–

Test for Reducing Agent:

Use of an Oxidising Agent e.g. acidified potassium manganate (VII)

Observation: Purple solution decolourises

Chemistry behind it: MnO₄^–(aq) + 8H⁺(aq) + 5e^– => Mn²⁺(aq) + 4H₂O(l)

YouTube Video Tutorial

Let’s take a look at the YouTube Video now….

Length of video: 16.11 minutes

Direct video link: https://youtu.be/1YQsHwUrT2c

I hope you find the content easy for your understanding and if you have any questions, leave me a comment below. Feel free to share this blog post with your friends and learn the key O-Level Pure Chemistry concepts together.

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PS: Under related articles below, there are several blog post discussions and questions related to Redox Reaction concepts. You can also do a keyword search using the search box at the top right hand corner.

Related Articles:

• O Level Chemistry – Analogy for Oxidising & Reducing Agents
• O Level Chemistry Question: Redox Reaction
• O Level Chemistry: Redox Reaction Question 3
• O Level Chemistry – More Questions on REDOX
• O Level Chemistry: Redox Reactions

Sean Chua

Winners Education Centre Pte. Ltd.

Many know me as the Ten Year Series book author for JC A-Level H2 Chemistry and O-Level Pure Chemistry. My 19+ years of coaching experience (since 1999) with more than 1500 students from 180+ JCs and Secondary Schools has allowed me to understand the true reasons why students are not able to perform well in Chemistry. Most importantly, my strength lies in using everyday analogies (even grandmothers can understand!) to simplify abstract concepts. Also, my teaching methodology has been designed to be fun, enjoyable and effective for my students. If you want to have an enjoyable time learning Chemistry and being motivated to excel in Chemistry, contact me today at 98287357