This worked example covers Balancing Combustion Equations within Combustion for GCSE Chemistry. Revise Combustion in Organic Chemistry for GCSE Chemistry with 20 exam-style questions and 15 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 5 of 12 in this topic. Treat this as a marking guide for what examiners are looking for, not just a fact list.
Topic position
Section 5 of 12
Practice
20 questions
Recall
15 flashcards
🧮 Balancing Combustion Equations
Combustion equations follow predictable patterns. Here's how to write them:
Step 1: Complete Combustion Pattern
Hydrocarbon + O₂ → CO₂ + H₂O
• All carbon becomes CO₂
• All hydrogen becomes H₂O
• Balance carbons, then hydrogens, then oxygens
Hydrocarbon + O₂ → CO₂ + H₂O
• All carbon becomes CO₂
• All hydrogen becomes H₂O
• Balance carbons, then hydrogens, then oxygens
Example: Propane (C₃H₈)
C₃H₈ + ?O₂ → ?CO₂ + ?H₂O
1. Carbons: 3 C atoms → 3CO₂
2. Hydrogens: 8 H atoms → 4H₂O (need 8 H total)
3. Oxygens: (3×2) + (4×1) = 10 O atoms → 5O₂
Answer: C₃H₈(g) + 5O₂(g) → 3CO₂(g) + 4H₂O(l)
C₃H₈ + ?O₂ → ?CO₂ + ?H₂O
1. Carbons: 3 C atoms → 3CO₂
2. Hydrogens: 8 H atoms → 4H₂O (need 8 H total)
3. Oxygens: (3×2) + (4×1) = 10 O atoms → 5O₂
Answer: C₃H₈(g) + 5O₂(g) → 3CO₂(g) + 4H₂O(l)
Example: Incomplete Combustion of Butane
2C₄H₁₀ + 9O₂ → 8CO + 10H₂O
Check: C: 2×4=8 ✓, H: 2×10=20→10H₂O ✓, O: 9×2=18; 8+10=18 ✓
2C₄H₁₀ + 9O₂ → 8CO + 10H₂O
Check: C: 2×4=8 ✓, H: 2×10=20→10H₂O ✓, O: 9×2=18; 8+10=18 ✓