Introduction – What is a Redox Reaction?
The Redox Reaction chapter in Class 11 Chemistry is one of the most conceptually important chapters for CBSE students.
Here, you learn how oxidation and reduction are not just about oxygen and hydrogen but about electron transfer, the very foundation of chemical change.
A Redox Reaction occurs when oxidation (loss of electrons) and reduction (gain of electrons) happen simultaneously in a chemical reaction.
The word “Redox” itself is derived from Reduction + Oxidation.
🧭 Chapter Overview – NCERT Class 11 Chemistry Redox Reaction
| Topic | Concept Summary |
|---|---|
| Oxidation and Reduction | Electron transfer process |
| Oxidizing and Reducing Agents | Species involved in oxidation/reduction |
| Oxidation Number | Rules and calculation steps |
| Balancing Redox Reactions | Ion-electron and oxidation number methods |
| Redox Reactions in Daily Life | Real-world chemical examples |
| Types of Redox Reactions | Combination, decomposition, displacement, disproportionation |
📘 NCERT Solutions for Class 11 Chemistry Chapter – Redox Reactions
Below are some key NCERT exercise questions and solutions with clear explanations based on the latest CBSE Class 11 syllabus (2025).
Q1. What is Oxidation and Reduction?
Answer:
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Oxidation: Loss of electrons, addition of oxygen, or removal of hydrogen.
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Reduction: Gain of electrons, addition of hydrogen, or removal of oxygen.
📘 Example:
Zn + CuSO₄ → ZnSO₄ + Cu
Here, Zn is oxidized (loses electrons) and Cu²⁺ is reduced (gains electrons).
Q2. Define Oxidizing and Reducing Agents.
Answer:
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Oxidizing Agent: The substance that causes oxidation of another and gets reduced itself.
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Reducing Agent: The substance that causes reduction of another and gets oxidized itself.
📘 Example:
2Na + Cl₂ → 2NaCl
Here, Na acts as the reducing agent, and Cl₂ acts as the oxidizing agent.
Q3. What is Oxidation Number? Give Example.
Answer:
The oxidation number of an element is the hypothetical charge assigned to it if all bonds were ionic.
📘 Example:
In H₂O, oxidation number of H = +1, O = -2.
Q4. Explain the Ion-Electron Method of Balancing Redox Reactions.
Answer:
This method is used to balance redox equations in acidic or basic media.
Steps:
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Split the equation into two half-reactions (oxidation and reduction).
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Balance the atoms other than oxygen and hydrogen.
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Balance oxygen using H₂O and hydrogen using H⁺ (acidic medium) or OH⁻ (basic medium).
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Balance the charge by adding electrons.
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Combine both half-reactions ensuring electrons cancel out.
📘 Example:
Fe²⁺ + Cr₂O₇²⁻ + H⁺ → Fe³⁺ + Cr³⁺ + H₂O
Q5. What is a Disproportionation Reaction?
Answer:
When the same element in a compound is simultaneously oxidized and reduced, it is called a Disproportionation Reaction.
📘 Example:
Cl₂ + H₂O → HCl + HOCl
Here, chlorine is both oxidized (in HOCl) and reduced (in HCl).
🧮 Important Concepts and Formulas
| Concept | Formula/Rule |
|---|---|
| Oxidation Number | Apparent charge on atom after ionic separation |
| Electrons Transferred (n) | Total change in oxidation numbers |
| Balancing Rule | Total increase = Total decrease in oxidation numbers |
💡 Applications of Redox Reactions in Real Life
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Batteries & Electrochemical Cells: Electricity generation through redox processes.
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Corrosion: Rusting of iron involves redox reaction.
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Photosynthesis: Conversion of light energy into chemical energy.
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Combustion: Every burning process is a redox reaction.
🎯 Exam-Focused Preparation Tips
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Memorize oxidation number rules.
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Practice all NCERT examples and in-text questions.
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Revise common oxidizing and reducing agents.
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Learn to balance equations using both methods.
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Use real-life examples for conceptual clarity.
