Homologous series
Carbon Compounds (School Level) · Chemistry
Study notes
The first three alkanes are CH₄, C₂H₆, C₃H₈. Predict the 4th and 5th members. Step 1: Each member differs by CH₂. Step 2: 4th = C₃H₈ + CH₂ = C₄H₁₀ (butane). Step 3: 5th = C₄H₁₀ + CH₂ = C₅H₁₂ (pentane). Step 4: Check formula CₙH₂ₙ₊₂: n=4 → C₄H₁₀ ✓; n=5 → C₅H₁₂ ✓. They share properties: all burn similarly, bp rises with size.