Which one of the following orders is not in accordance with the property stated against it?
- F2 > Cl2 > Br2 > I2 : Bond dissociation energy
- F2 > Cl2 > Br2 > I2 : Oxidising power
- HI > HBr > HCl > HF : Acidic property in water
- F2 > Cl2 > Br2 > I2 : Electronegativity.
Answer
(1) F2 > Cl2 > Br2 > I2 : Bond dissociation energy
Solution
As per NCERT, the bond dissociation enthalpy of F2 is smaller than that of Cl2 because of large electron–electron (lone pair) repulsion among the lone pairs in the small F2 molecule.
⇒ Correct order of bond dissociation enthalpy: Cl2 > Br2 > F2 > I2
∴ Order (1) is not in accordance with the property.
The other orders are correct: oxidising power F2 > Cl2 > Br2 > I2; acid strength in water HI > HBr > HCl > HF (H–X bond enthalpy decreases down the group); electronegativity F > Cl > Br > I.
Answer: (1)