Question

In which of the following pairs indicated, the bond has less bond dissociation energy?

(a)- (I)
(b)- (II)
(c)- Both are equal
(d)- Cannot be determined

Answer 1

Bond dissociation energy is the energy required for the bond to break. The bond dissociation energy for the triple bond is greater than the double bond and the bond dissociation energy of the double bond is greater than the single bond.

Complete step by step solution:
Bond dissociation energy is the energy required for the bond to break. The stronger the bond, the more the energy will be required, so we can say that the bond dissociation energy for the triple bond is greater than the double bond and the bond dissociation energy of the double bond is greater than the single bond.
- In both the compounds, the double bonds have to be broken, so the bond dissociation energy has to be decided to the resonance factor.
- In compound (I), the double bond has only one single bond to show the conjugation, but in compound (II), the double has two single bonds to show the conjugation. So, in compound (I) the tendency of conjugation is lesser than the tendency of conjugation in compound (II) therefore, the double bond in compound (II) will be stronger than the double bond in compound (I).
- Hence, the bond dissociation energy required in the compound (I) will be lesser than the bond dissociation energy in compound (II).
So, the correct answer is “Option A”.

Note: As the resonance increases, the stability of the compound increases due to which more energy is required to break the compound. The bond dissociation energy of an ionic bond is more than the bond dissociation energy of the covalent bond.