Question

Which of the following bond enthalpies is the least: \[ C = C, C = O, C \equiv N, C = N \]

• A. \( C = C \)
• B. \( C = O \)
• C. \( C \equiv N \)
• D. \( C = N \)

Hint:

The strength of a bond increases with the number of shared electrons. Triple bonds are stronger than double bonds, which are stronger than single bonds.

Answer 1

The Correct Option is A

The bond enthalpy refers to the energy required to break one mole of bonds in a molecule in its gaseous phase. The strength of a bond is influenced by factors such as bond length and the electronegativity difference between the atoms involved.

1. Step 1: Compare the types of bonds. - A double bond (like \( C = C \) and \( C = O \)) is stronger than a single bond but weaker than a triple bond (like \( C \equiv N \)). - A triple bond is the strongest and thus has the highest bond enthalpy.

2. Step 2: Analyze each bond. - The C = C bond is weaker compared to the C = O and C \equiv N bonds because oxygen and nitrogen are more electronegative than carbon, making their bonds stronger. - The C = O bond is stronger than C = C because oxygen is more electronegative. - The C \equiv N bond is stronger than C = O and C = C due to the triple bond. Thus, the least bond enthalpy is found for the C = C bond.