Question

Assertion : F - F bond has low bond dissociation energy.
Reason : The fluorine has lower reactivity.

• A. If both assertion and reason are true and reason is a correct explanation of the assertion
• B. If both the assertion and reason are true but the reason is not a correct explanation of the assertion
• C. If the assertion is true but the reason is false
• D. If both the assertion and reason are false

Answer 1

Answer: (C)

Lower value of bond dissociation energy of fluorine is due to the high inter electronic repulsions between nonbonding electrons of the $2p$-orbital of small sized fluorine. As a result $F-F$ bond is weaker as comparison to $Cl - Cl$ and $Br - Br$ bonds.

Bond dissociation energy

$ F-F \,\,\,\,\,\,38 \,Kcal /\, mole$

$Cl - Cl\,\,\,\,\,\,\,57 \,K \,cal / \,mole$

$Br - Br \,\,\,\,\,\,\,\, 45.5 \,K cal/\,mole $

$I-I \,\,\,\,\,\,\,\,\,,35.6\, K\, cal/\,mole $