NCERT Class 11 Chemistry Chemistry Part II: Chapter 1 — Redox Reactions
This chapter introduces Redox Reactions, a crucial category in Chemistry dealing with simultaneous oxidation and reduction. It explains the classical definitions of oxidation (addition of oxygen or electronegative elements, removal of hydrogen or electropositive elements) and reduction (removal of oxygen or electronegative elements, addition of hydrogen or electropositive elements). The chapter highlights the interconnectedness of these processes, leading to the concept of 'redox' reactions. It also outlines the learning objectives, including identifying redox reactions, defining key terms like oxidant and reductant, understanding electron transfer mechanisms, and classifying redox reactions. The importance of redox reactions in various industrial, biological, and environmental applications is emphasized, setting the stage for deeper exploration of balancing equations and electrode processes.
Quick info
| Board | CBSE / NCERT |
|---|---|
| Class | Class 11 |
| Subject | Chemistry |
| Book | Chemistry Part II |
| Chapter | Chapter 1 — Redox Reactions |
| Language | English |
| PDF type | NCERT Textbook |
| Session | CBSE 2026 |
| Reading time | 5 minutes |
| Word count | 974 |
Learning outcomes
- Identify redox reactions as processes involving simultaneous oxidation and reduction.
- Define oxidation, reduction, oxidant, and reductant.
- Explain the mechanism of redox reactions through electron transfer.
- Use oxidation numbers to identify oxidants and reductants.
- Classify redox reactions into combination, decomposition, displacement, and disproportionation.
- Balance chemical equations using oxidation number and half-reaction methods.
Vocabulary
| Word | Meaning |
|---|---|
| Oxidation | Addition of oxygen/electronegative element or removal of hydrogen/electropositive element. |
| Reduction | Removal of oxygen/electronegative element or addition of hydrogen/electropositive element. |
| Redox Reaction | A reaction where oxidation and reduction occur simultaneously. |
| Oxidant | A substance that causes oxidation (gets reduced). |
| Reductant | A substance that causes reduction (gets oxidized). |
| Electronegative element | An element that readily attracts electrons in a chemical bond. |
| Electropositive element | An element that readily loses electrons in a chemical bond. |
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Practice questions
- In the reaction H2S(g) + Cl2(g) → 2 HCl(g) + S(s), identify the species undergoing oxidation and reduction. Answer: H2S is oxidized, and Cl2 is reduced.
- Define the term 'oxidant' and 'reductant'. Answer: An oxidant (oxidizing agent) is a substance that causes oxidation and gets reduced itself. A reductant (reducing agent) is a substance that causes reduction and gets oxidized itself.
- Give an example of oxidation involving the addition of an electronegative element. Answer: Mg(s) + Cl2(g) → MgCl2(s)
- What is the classical definition of reduction? Answer: Removal of oxygen from a compound or addition of hydrogen/electropositive element to a compound.
Frequently asked questions
What is the fundamental concept of redox reactions?
Redox reactions are chemical reactions where oxidation and reduction occur simultaneously, involving the transfer of electrons.
What are the classical definitions of oxidation?
Oxidation is classically defined as the addition of oxygen or an electronegative element to a substance, or the removal of hydrogen or an electropositive element from a substance.
What is the classical definition of reduction?
Reduction is classically defined as the removal of oxygen or an electronegative element from a substance, or the addition of hydrogen or an electropositive element to a substance.
Why are redox reactions important?
Redox reactions are vital in various fields like industry, biology, metallurgy, and environmental science, including processes like burning fuels, electrochemistry, and corrosion.
What is the difference between an oxidant and a reductant?
An oxidant causes oxidation in another substance and is itself reduced, while a reductant causes reduction in another substance and is itself oxidized.
Can oxidation occur without reduction?
No, oxidation and reduction always occur simultaneously in a redox reaction; one cannot happen without the other.
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NCERT Class 11 Chemistry — Chemistry Part II — Chapter 1 — Redox Reactions. Verified by NCERT Help Editorial Team. Reviewed on 29 Jul 2026. Last updated 10 Aug 2026.