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O-Level Chemistry: Tests for Oxidising Agents and Reducing Agents

Test for Oxidising Agents and Reducing Agents - O Level Pure Chemistry Tuition
Photo Credit: Pete (Creative Commons)

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.