Science · Class 10
Chemical Reactions and Equations
Balancing equations, types of reactions, oxidation-reduction, and corrosion.
3 sections15–25 min read6 MCQs · 2 examples
Chapter Overview
A balanced equation has equal atoms of each element on both sides.
Chemical reactions rearrange atoms to form new substances. Learn to write balanced equations, identify combination, decomposition, displacement, double displacement, and redox reactions with everyday examples.
Types of Reactions
- Combination: A + B → AB (e.g. 2Mg + O₂ → 2MgO)
- Decomposition: AB → A + B (electrolysis, heat, light)
- Displacement: A + BC → AC + B (more reactive displaces less)
- Double displacement: AB + CD → AD + CB (precipitate/gas/water)
Redox
- Oxidation: gain of oxygen or loss of hydrogen/electrons
- Reduction: loss of oxygen or gain of hydrogen/electrons
- Oxidising agent gets reduced; reducing agent gets oxidised
Solved Examples
Step-by-step solutions — read each step before checking the final answer.
Balance equation
Balance: Fe + H₂O → Fe₃O₄ + H₂
- 13Fe + 4H₂O → Fe₃O₄ + 4H₂
- 2Check: Fe=3, O=4, H=8 both sides
Answer
3Fe + 4H₂O → Fe₃O₄ + 4H₂
Identify reaction type
Zn + CuSO₄ → ZnSO₄ + Cu. Type?
- 1Zn displaces Cu from solution
- 2More reactive Zn replaces Cu
Answer
Displacement reaction
Key Points to Remember
- ✓ State symbols: (s), (l), (g), (aq)
- ✓ Corrosion: oxidation of metals (rusting of iron)
- ✓ Rancidity: oxidation of fats in food
Exam Tips
- • Balance by hit-and-trial or algebraic method
- • Never change subscripts
- • Identify oxidised and reduced species in redox
Practice MCQs — Chemical Reactions and Equations
Test your understanding with topic-wise multiple choice questions. Explanations appear after each answer.
Question 1 of 6Score: 0/0
Rusting of iron is: