Question

i. Arrange the following in decreasing order of bond dissociation enthalpy.
F2 , Cl2 , Br2 , I2
ii. Bi does not form pπ-pπ bonds. Give reason for the observation.
iii.Electron gain enthalpy of oxygen is less negative than sulphur. Justify

Answer 1

Halogens

Explanation:

• For the given molecules, the decreasing order would be as follow,

        Cl2 ≥ Br2 ≥ F2 ≥ I2

• Now, fluorine doesn't have a d-orbital; thus, it is smaller in size, experiencing repulsion between the electron, making the bond weaker compare to other halogens. Thus, the above order is observed.
• Br doesn't form pπ-pπ bonds due to its relatively larger size.
• Now, because of its small size and compact nature of oxygen atom, it has less electron gain enthalpy or simply it is less negative than sulphur.