Chapter 1: Chemical Reactions and Equations (Part 3) SSLC | Class 10
Intoduction
In continuation of Chapter 1 (Chemical Reactions and Equations – Part 2), this part focuses on Oxidation and Reduction reactions (Redox Reactions), which are fundamental concepts in understanding how chemical changes occur in everyday life.
These reactions are not only important for exams but also help explain real-life processes such as rusting of iron, corrosion of metals, and spoilage of food (rancidity).
Oxidation and Reduction (Redox Reactions)
Oxidation
Definition:Oxidation is a chemical process in which a substance gains oxygen during a reaction.
Key Idea:👉 Gain of oxygen = Oxidation
Example:2Cu + O₂ → 2CuO
Copper (Cu) combines with oxygen (O₂)
Forms copper oxide (CuO)
Hence, copper is oxidized
Reduction
Definition:Reduction is a chemical process in which a substance loses oxygen during a reaction.
Key Idea:👉 Loss of oxygen = Reduction
Example:CuO + H₂ → Cu + H₂O
Copper oxide loses oxygen
Becomes copper (Cu)
Hence, copper oxide is reduced
Redox Reaction (Oxidation + Reduction)
Definition:A reaction in which oxidation and reduction occur simultaneously is called a Redox Reaction.
Key Concept:👉 One substance is oxidized, while another is reduced
Example:CuO + H₂ → Cu + H₂O
CuO → reduced to Cu
H₂ → oxidized to H₂O
Conclusion:👉 Both processes happen together → Redox Reaction
Corrosion and Rancidity
Definition:Corrosion is the process in which metals are slowly damaged by substances like moisture, air, or acids present in the environment.
Examples:
Rusting of iron (reddish-brown coating)
Black coating on silver
Green coating on copper
Effects of Corrosion
Damages car bodies, bridges, iron railings, ships
Weakens metal structures
Causes economic loss
Prevention Methods
Painting metal surfaces
Powder coating
Applying oil or grease
Galvanization (coating with zinc)
Rancidity
Definition:Rancidity is the process in which fats and oils get oxidized, causing bad smell and taste in food.
Causes
Exposure to oxygen
Heat and sunlight
Prevention Methods
Store food in airtight containers
Refrigeration
Keep away from sunlight
Use antioxidants
Flush with nitrogen gas (e.g., chips packets)
Most expected questions
1.MnO2 + 4 HCl ------ MnCl2 + 2 H2 O + Cl2 : Find the substance which is oxidized and reduced
MnO2 is reduced to MnCl2
Hcl is oxidized to Cl2
2. Which gas is used in the packets of chips and why
Nitrogen gas because to prevent chips from turning rancid
3. Why do we apply Paint on Iron articles
To prevent it from rusting or corrosion
4. How to prevent corrosion?
Painting the metal surface
Galvanizing
Anodising
Chrome plating
Powder coating the surface
Coating the iron surface with oil or grease
5. How to prevent rancidity
Keep the food in air tight container
Keep the food in refrigerator
Flush the oilnorvfat food with nitrogen gas
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