Final answer:
Alkenes are hydrocarbons with one or more carbon-carbon double bonds and are a type of unsaturated hydrocarbon. The simplest alkene is ethene with the molecular formula C2H4.
Step-by-step explanation:
The correct description of an alkene is that it is a hydrocarbon compound that contains a carbon-carbon double bond. So, the correct statement is: 1) Alkene is a hydrocarbon compound that contains a carbon-carbon double bond. Alkenes are a type of unsaturated hydrocarbon, which means they contain less than the maximum number of hydrogen atoms they could possibly bond with the number of carbon atoms present due to the presence of double or triple bonds.
The simplest alkene is ethene, also known as ethylene, which has the formula C2H4 with one double bond between the two carbon atoms. In contrast, alkynes are hydrocarbons with a carbon-carbon triple bond, and alkanes only have carbon-carbon single bonds.