Chemical Reactions and Equations – Class 10 NCERT Solutions & Revision Notes
Comprehensive notes for Class 10 Chemistry Chapter 1. Balancing chemical equations, redox reactions, combination, displacement, and board examination notes.
Chemical Reactions and Equations – Complete Study Guide
A chemical reaction is a process in which one or more substances (reactants) transform into new chemical substances (products) with distinct physical and chemical properties. During a chemical reaction, existing chemical bonds break and new chemical bonds are created.
How to Balance Chemical Equations
A balanced chemical equation contains equal numbers of atoms of each element on both the reactant and product sides, adhering to the Law of Conservation of Mass.
Balancing Iron with SteamUnbalanced: Fe (s) + H₂O (g) ──> Fe₃O₄ (s) + H₂ (g) Balanced: 3Fe (s) + 4H₂O (g) ──> Fe₃O₄ (s) + 4H₂ (g)
5 Major Types of Chemical Reactions
| Type of Reaction | Definition | Chemical Equation Example |
|---|---|---|
| Combination | Two or more reactants unite into a single product. | CaO (Quicklime) + H₂O → Ca(OH)₂ (Slaked lime) + Heat |
| Decomposition | A single compound breaks down into simpler products on applying heat, light, or electricity. | 2FeSO₄ (Green) ──[Heat]──> Fe₂O₃ (Red-brown) + SO₂ (g) + SO₃ (g) |
| Displacement | A more reactive element replaces a less reactive metal from its aqueous salt solution. | Zn (s) + CuSO₄ (aq, Blue) → ZnSO₄ (aq, Colourless) + Cu (s) |
| Double Displacement | Mutual exchange of ions between two ionic compounds to form a precipitate. | Na₂SO₄ (aq) + BaCl₂ (aq) → BaSO₄ (White ppt) + 2NaCl (aq) |
| Redox Reaction | Simultaneous oxidation and reduction processes. | CuO + H₂ ──[Heat]──> Cu + H₂O |
Oxidation and Reduction (Redox)
- Oxidation: Gain of oxygen or loss of hydrogen / loss of electrons.
- Reduction: Loss of oxygen or gain of hydrogen / gain of electrons.
- Oxidizing Agent: Substance that supplies oxygen or accepts electrons.
- Reducing Agent: Substance that removes oxygen or loses electrons.
Corrosion and Rancidity
• Iron Rusting:
4Fe + 3O₂ + 2xH₂O → 2Fe₂O₃·xH₂O (Hydrated ferric oxide)• Silver Tarnishing:
2Ag + H₂S → Ag₂S (Black coating) + H₂• Copper Corrosion: Forms green basic copper carbonate
CuCO₃·Cu(OH)₂.Rancidity: Aerial oxidation of fats and oils causing unpleasant smell and taste. Prevented by nitrogen flushing, antioxidants (BHA/BHT), and vacuum sealing.
Indexed Topics & Examination Keywords
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