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Wednesday, August 26, 2026

Decomposition reactions are opposite to combination reactions. In a decomposition reaction, a single substance decomposes to give two or more substances.

Decomposition Reaction | Class 10 CBSE Science
🧪 Decomposition Reaction
अपघटन अभिक्रिया — Class 10 CBSE Science
1️⃣ Description / परिचय

English

A decomposition reaction is a chemical reaction in which a single substance breaks down into two or more simpler substances.
AB → A + B

हिन्दी

अपघटन अभिक्रिया वह रासायनिक अभिक्रिया है जिसमें एकल पदार्थ टूटकर दो या दो से अधिक सरल पदार्थ बनाता है।
AB → A + B
Remember / याद रखें:

Combination:
A + B → AB

Decomposition:
AB → A + B

अर्थात decomposition reaction, combination reaction के pattern के विपरीत होती है।
2️⃣ Attractive Animation / Animation द्वारा समझें
One Compound → Two or More Simpler Substances
एक यौगिक → दो या अधिक सरल पदार्थ
AB
A
B
AB → A + B
3️⃣ Basic Concept / मूल अवधारणा
Example 1 — Thermal Decomposition
CaCO₃ → CaO + CO₂
Calcium carbonate decomposes on heating to form calcium oxide and carbon dioxide.

कैल्शियम कार्बोनेट गर्म करने पर कैल्शियम ऑक्साइड और कार्बन डाइऑक्साइड में टूट जाता है।
Example 2 — Electrolytic Decomposition
2H₂O → 2H₂ + O₂
Water decomposes into hydrogen and oxygen by electricity.
Example 3 — Photochemical Decomposition
2AgCl → 2Ag + Cl₂
Silver chloride decomposes in sunlight.
4️⃣ Types of Decomposition Reactions
Type Energy / Condition Example
Thermal Heat CaCO₃ → CaO + CO₂
Electrolytic Electricity 2H₂O → 2H₂ + O₂
Photochemical Sunlight 2AgCl → 2Ag + Cl₂
Exam Trick:

Heat → Thermal decomposition
Electricity → Electrolytic decomposition
Sunlight → Photochemical decomposition
5️⃣ Fully Solved Example / पूर्ण हल
Question: Identify the type of reaction: CaCO₃ → CaO + CO₂
CBSE
Step 1: Reactant = CaCO₃

Only one reactant is present.

Step 2: Products = CaO and CO₂

There are two products.

Step 3: One substance breaks down into two substances.

Therefore, it is a: Decomposition Reaction.

Because heat is required, it is specifically a: Thermal Decomposition Reaction.

हिन्दी: CaCO₃ एक पदार्थ है जो गर्म करने पर CaO तथा CO₂ में टूट जाता है। इसलिए यह अपघटन अभिक्रिया है।
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1️⃣2️⃣ Quick Revision / त्वरित Revision
AB → A + B
ONE SUBSTANCE → TWO OR MORE SUBSTANCES

✔ Thermal Decomposition → Heat
CaCO₃ → CaO + CO₂

✔ Electrolytic Decomposition → Electricity
2H₂O → 2H₂ + O₂

✔ Photochemical Decomposition → Sunlight
2AgCl → 2Ag + Cl₂
CBSE Exam Trick:

One reactant + Two or more products ↓ Decomposition Reaction

एक पदार्थ → दो या अधिक पदार्थ ↓ अपघटन अभिक्रिया
1️⃣3️⃣ Final Concept
🧪 DECOMPOSITION REACTION

ONE SUBSTANCE ↓ BREAKS DOWN ↓ TWO OR MORE SUBSTANCES

AB → A + B

अपघटन अभिक्रिया में एकल पदार्थ दो या दो से अधिक सरल पदार्थों में टूट जाता है।
1️⃣2️⃣ Final Revision / अंतिम Revision
AB → A + B
ONE SUBSTANCE → TWO OR MORE SUBSTANCES

🔥 Heat → Thermal Decomposition
CaCO₃ → CaO + CO₂

⚡ Electricity → Electrolytic Decomposition
2H₂O → 2H₂ + O₂

☀️ Sunlight → Photochemical Decomposition
2AgCl → 2Ag + Cl₂
CBSE Exam Shortcut:

One Reactant + Two or More Products ↓ DECOMPOSITION REACTION

एक अभिकारक + दो या अधिक उत्पाद ↓ अपघटन अभिक्रिया
🏆 Final Concept
🧪 DECOMPOSITION REACTION

ONE SUBSTANCE ↓ BREAKS DOWN ↓ TWO OR MORE SUBSTANCES

AB → A + B

अपघटन अभिक्रिया में एकल पदार्थ दो या दो से अधिक सरल पदार्थों में टूट जाता है।