The correct option is C2H2.
Explanation
Hydrocarbons are organic compounds consisting entirely of hydrogen and carbon. They are classified based on the type of bonding between carbon atoms:
- Saturated Hydrocarbons (Alkanes): Contain only single bonds between carbon atoms. They follow the general formula CnH2n+2.
- Unsaturated Hydrocarbons (Alkenes and Alkynes): Contain at least one double or triple bond between carbon atoms. Alkenes follow CnH2n, and Alkynes follow CnH2n-2.
Analysis of Options:
- C2H2 C2H2 (Ethyne): This fits the general formula for alkynes (CnH2n-2 where n=2). It contains a carbon-carbon triple bond (H-C≡C-H), making it unsaturated.
- C2H6 C2H6 (Ethane): This fits the general formula for alkanes (CnH2n+2 where n=2). It contains only single bonds, making it saturated.
- CH4 CH4 (Methane): This fits the general formula for alkanes (where n=1). It contains only single bonds, making it saturated.
- C3H8 C3H8 (Propane): This fits the general formula for alkanes (where n=3). It contains only single bonds, making it saturated.
Key Takeaway:
Unsaturated hydrocarbons are identified by the presence of multiple bonds (double or triple) between carbon atoms, which results in fewer hydrogen atoms compared to a saturated hydrocarbon with the same number of carbon atoms.