Remember the first four alkanes using the phrase:
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- Methane — CH₄ (1 carbon)
- Ethane — C₂H₆ (2 carbons)
- Propane — C₃H₈ (3 carbons)
- Butane — C₄H₁₀ (4 carbons)
To use the general formula CₙH₂ₙ₊₂: double the number of carbons, then add 2. For propane (n=3): 2×3+2 = 8. Formula = C₃H₈. Check: 3 carbons and 8 hydrogens — correct!
This memory aid covers Memory Aid: MEPB — The First Four Alkanes within Alkanes for GCSE Chemistry. Topic 38: Alkanes It is section 9 of 12 in this topic. Use it for quick recall, then test yourself straight afterwards so the memory aid becomes usable in an answer.
Practice questions for Alkanes
What is the general formula for the alkane homologous series?
Explain why the boiling point of alkanes increases as the chain length increases.
Quick recall flashcards
Formula for ethane?
C₂H₆
Formula for butane?
C₄H₁₀