Many students in my weekly JC1 GCE A-Level H2 Chemistry Tuition Classes in Singapore told me that they are struggling to understand the concepts regarding Redox Reactions. This is usually taught in JC1 Topic 1: Mole Concepts & Stoichiometry in their Junior College’s lectures and tutorial classes. They seems lost and don’t even know how to start when looking at a Redox Reactions question.
Many of them have approached their JC teacher or recommended H2 Chemistry tutor but still not able to solve redox reactions question confidently.
So, before you work on another Redox Reactions question, do go through the following:
4 steps on How to Solve Redox Reactions in JC A-Level H2 Chemistry
1. Describe and explain redox processes in terms of electron transfer and/or of changes in oxidation number (oxidation state)
Reduction and Oxidation processes may be defined in terms of electron transfer and/or changes in oxidation number (oxidation state).
- Reduction: A process whereby a substance gains electrons, resulting in a decrease in oxidation number
- Oxidation: A process whereby a substance loses electrons. resulting in an increase in oxidation number
- Reducing Agent (Reductant): A substance that gives electrons to another, itself being oxidised in the process
- Oxidising Agent (Oxidant): A substance that takes in electrons from another, itself being reduced in the process
Next, you would need to understand that in a redox reaction, there is a transfer of electrons from the reducing agent (who loses electrons and is being oxidised) to the oxidising agent (who gains electrons and is being reduced).
2. Construct redox equations using the relevant half-equations
For most examination questions, the full redox equation is not given directly in the question. So, students would need to be able to come out with it. This is only possible if you are able to work out the half-equations (both the oxidation half and the reduction half) on your own.
From there, you would need to combine the oxidation half equation and the reduction half equation to form the full redox equation. Do note that half equations will always contain electrons in it while full redox equations will not have any electrons since they have been cancelled out.
3. Perform calculations, using the mole concepts, involving redox reactions
What you have learned previously in Mole Concepts or Mole Calculations will come into good use here. You will usually be required to calculate terms involving Mole, Volume and Molar Concentration.
You must also be aware that the number of moles of electrons lost by the reducing agent must be equal to the number of electrons gained by the oxidising agent.
In another word, to solve such questions, you need to determine the mole of electrons that are being transferred.
4. Deduce stoichiometric relationships from calculations such as those in (3) above
From there, you will have to deduce the stoichiometric relationships to solve the question using the balanced equation.
The following video will show you an example of how i apply the steps to solve a Redox Reaction. Enjoy watching!
Length of video: 5.35 minutes
Direct video link: https://youtu.be/CJRUP2iKohU
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 proper Chemistry Concepts together.
Subscribe to my blog to receive 2 updates per month sent to your email!
PS: Under related articles below, there are several blog post discussions and questions related to Balancing Redox Equations and Solving Redox Reactions Questions. You can also do a keyword search using the search box at the top right hand corner.
If you are based in Singapore and needs help in Chemistry, feel free to give us a call to find out more about our A-Level H2 tuition classes.