Chapter 3: Chemical Reactions and Equations Notes – Class 10 Science (MSBSHSE)

This chapter explores how substances interact, transform, and can be represented through balanced equations. Learn important types, rules, and solutions—all crafted to help you excel in the SSC board exam.

🔹 1. What is a Chemical Reaction?

A chemical reaction is a process where reactants change into new substances called products, involving breaking and forming chemical bonds.

• Reactants → Products
• Energy may be released or absorbed
• It’s a **reproducible** and **quantitative** transformation

🔹 2. Chemical Equation and Balancing

Chemical equations symbolically represent reactions with formulas and stoichiometric coefficients.

Mg + 2HCl → MgCl₂ + H₂

Balance by adjusting coefficients so atoms of each element are equal on both sides—this obeys the Law of Conservation of Mass.

🔹 3. Types of Chemical Reactions

• Combination (Synthesis): A + B → AB
  Example: 2H₂ + O₂ → 2H₂O
• Decomposition: AB → A + B
  Example: 2H₂O₂ → 2H₂O + O₂ (catalyst: MnO₂)
• Displacement: A + BC → AC + B
  Example: Zn + 2HCl → ZnCl₂ + H₂
• Double Displacement: AB + CD → AD + CB
  Example: AgNO₃ + NaCl → AgCl↓ + NaNO₃
• Redox Reactions: Involve transfer of electrons (oxidation & reduction). Example: 2Fe₂O₃ + 3C → 4Fe + 3CO₂
• Exothermic vs Endothermic: • Exothermic: releases heat (combustion) • Endothermic: absorbs heat (photosynthesis)

🔹 4. Law of Conservation of Mass

Mass cannot be created or destroyed during chemical reactions—total mass of reactants = total mass of products.

🔹 5. Activity Series of Metals

Metals listed in decreasing ability to displace hydrogen from acids or water:

More reactive metal displaces less reactive metal from its compound.

🔹 6. Oxidation & Reduction

Oxidation: Gain of oxygen/loss of hydrogen or electrons
Reduction: Loss of oxygen/gain of hydrogen or electrons

• Example: Zn + CuSO₄ → ZnSO₄ + Cu - Zn oxidized (loses electrons) - Cu²⁺ reduced (gains electrons)
• MnO₂ catalyzes decomposition of H₂O₂

🔹 7. Balancing Complex Equations

1. Write correct formulas for products/reactants
2. Balance elements one by one
3. Use lowest whole-number coefficients
4. Check conservation for each element

Example: C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O

🔹 8. Solved Examples

1. Reaction: P + O₂ → P₂O₅
   Balanced: 4P + 5O₂ → 2P₂O₅
2. Combustion: 2C₇H₆O₂ + 15O₂ → 14CO₂ + 6H₂O
3. Displacement: 2Al + 3CuSO₄ → Al₂(SO₄)₃ + 3Cu

🔹 9. Key Definitions & Terms

• Catalyst: Substance that speeds up reaction without being consumed.
• Precipitate: Solid formed from two reacting solutions.
• Reactant/Product: Substances before/after reaction

🔹 10. Exam Tips (Last 5 Years)

• Write balanced equations with state symbols.
• List reaction types with examples.
• Identify oxidation & reduction steps in a reaction.
• Explain displacement reactions using activity series.

🔗 You may also like:

• Chapter 1: Gravitation
• Chapter 2: Periodic Classification of Elements
• Chapter 3: Control and Coordination
• Class 10 Kumarbharati Textbook Solutions
• Class 10 All Subject Notes
• Class 10 English Paper Pattern

📘 Keep exploring for more Class 10 Science resources! Chapter 4 coming soon.