Which of the following statements about but-1-ene are true?
1 it can form a polymer
2 it contains C–C single bonds only
3 it conforms to the general formula CnH2n
4 it decolourises bromine water
5 it is saturated

Answer:

The name ‘but-1-ene’ indicates that it is an alkene. Alkenes have the following features:

• general formula is CnH2n
• they contain C=C double bonds and so are unsaturated
• they undergo addition reactions such as polymerisation (to produce a long chain polymer) and
  addition of bromine (so they decolourise bromine water – the test for unsaturation / presence
  of C=C double bonds).
  But-1-ene can form a polymer, it fits the general formula CnH2n and decolourises bromine water; and
  because it contains carbon-carbon double bonds it is not saturated.
  The answer is C