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Question:

Which one of the following order is correct for the bond dissociation enthalpy of halogen molecules?

Cl2>Br2>F2>I2

Br2>I2>F2>Cl2

F2>Cl2>Br2>I2

I2>Br2>Cl2>F2

Solution:

Bond dissociation energy of halogen family decreases down the group as the size of atom increases. The decreasing order for the bond dissociation enthalpy of halogen molecules is Cl2 57 kcal/mol > Br2 45.5 kcal/mol > F2 38 kcal/mol > I2 35.6 kcal/mol.