The question is incomplete, here is a complete question.
Which formula represents an alkene?
(a) \(CH_4\)
(b) \(C_2H_4\)
(c) \(C_2H_6\)
(d) \(C_2H_5OH\)
Answer : The correct option is, (b) \(C_2H_4\)
Explanation :
Hydrocarbons are the type of organic compound that contains only hydrogen and the carbon atoms.
Saturated hydrocarbon : These are those hydrocarbons in which all carbon atoms and hydrogen atoms are bonded together with single bonds. The general formula of saturated hydrocarbon (alkane) is, \(C_nH_{2n+2}\)
For example : Methane, Ethane, etc.
Unsaturated hydrocarbon : These are those hydrocarbons in which carbon-carbon atom bonded together with double or triple covalent bonds.
The general formula of unsaturated double bond hydrocarbon (alkene) is, \(C_nH_{2n}\)
The general formula of unsaturated triple bond hydrocarbon (alkyne) is, \(C_nH_{2n-2}\)
For example : Ethene, Butyne, etc.
As per question,
(a) \(CH_4\) : It is a saturated hydrocarbon and the name of this hydrocarbon is methane.
(b) \(C_2H_4\) : It is an unsaturated hydrocarbon and the name of this hydrocarbon is ethene.
(c) \(C_2H_6\) : It is a saturated hydrocarbon and the name of this hydrocarbon is ethane.
(d) \(C_2H_5OH\) : It is a saturated hydrocarbon and the name of this hydrocarbon is ethanol.
Hence, the formula represents an alkene is, \(C_2H_4\)
