Chemistry · Grades 10–12
Alkenes, alkynes and unsaturation · Revision sheet
Recognize bond types and the restrictions of simple formula patterns.
Learn the idea
Alkene
An alkene contains a C=C bond. An acyclic hydrocarbon with one double bond has formula CₙH₂ₙ.
Alkyne
An alkyne contains a C≡C bond. An acyclic hydrocarbon with one triple bond has formula CₙH₂ₙ₋₂.
Position
Position numbers distinguish where a multiple bond begins on the parent chain.
Not unique
A molecular formula may also fit rings or other unsaturation patterns, so connectivity is needed.
Explain without looking
- How many hydrogen atoms fewer are in ethene C₂H₄ than in ethane C₂H₆?
- Explain why an alkene formula should be checked against the stated number of rings and double bonds.
Further reading and review references
These are reference links, not copied exercises, institutional endorsement or proof of independent review.
Independent educational review required. Grade bands are approximate; these are not officially aligned curricula.