Which of the following hydrocarbons has a double bond in its carbon skeleton?
1) C3H8 2) C2H6 3) CH4 4) C2H4 5) C2H2
The Correct Answer and Explanation is:
The correct answer is 4) C2H4.
Explanation:
Hydrocarbons are compounds made up of carbon (C) and hydrogen (H) atoms. The types of hydrocarbons are categorized based on the bonds between the carbon atoms:
- Alkanes: hydrocarbons with only single bonds between carbon atoms.
- Alkenes: hydrocarbons containing at least one double bond between carbon atoms.
- Alkynes: hydrocarbons containing at least one triple bond between carbon atoms.
Let’s break down each option:
- C3H8 (Propane): This is an alkane. It consists of three carbon atoms connected by single bonds, and the remaining bonds are filled with hydrogen atoms. The formula follows the general formula for alkanes, CnH2n+2. There are no double or triple bonds in this molecule. Therefore, it does not have a double bond.
- C2H6 (Ethane): This is also an alkane. It contains two carbon atoms connected by a single bond, with each carbon atom bonded to three hydrogen atoms. Like propane, it follows the alkane formula, CnH2n+2, and contains no double bonds.
- CH4 (Methane): Methane is another alkane, with one carbon atom bonded to four hydrogen atoms. It has no double or triple bonds and is a simple example of a saturated hydrocarbon.
- C2H4 (Ethene or Ethylene): This is an alkene. Ethene contains two carbon atoms connected by a double bond (C=C). Each carbon atom is also bonded to two hydrogen atoms. Ethene follows the formula for alkenes, CnH2n, and is characterized by having at least one double bond. This is the correct answer.
- C2H2 (Ethyne or Acetylene): This is an alkyne, where the two carbon atoms are connected by a triple bond. Each carbon is bonded to one hydrogen atom. While it does contain a multiple bond, it has a triple bond, not a double bond, so it is not the correct answer.
Thus, C2H4 (ethene) is the only molecule in this list with a double bond between carbon atoms.