Identify the incorrect statement from the following :
- The acidic strength of HX (X = F, Cl, Br and I) follows the order: HF > HCl > HBr > HI.
- Fluorine exhibits -1 oxidation state whereas other halogens exhibit +1, +3, +5 and +7 oxidation states also.
- The enthalpy of dissociation of F2 is smaller than that of Cl2.
- Fluorine is stronger oxidising agent than chlorine.
Answer
(1) The acidic strength of HX (X = F, Cl, Br and I) follows the order: HF > HCl > HBr > HI.
Solution
(1) Incorrect: the H-X bond enthalpy decreases from HF to HI, so acidic strength increases: HF < HCl < HBr < HI.
(2) Correct: F is the most electronegative element and has no d orbitals, so it shows only -1; Cl, Br and I also show +1, +3, +5, +7.
(3) Correct: bond dissociation enthalpy of F2 (158.8 kJ mol-1) is smaller than that of Cl2 (242.6 kJ mol-1) due to large lone pair–lone pair repulsion in the small F2 molecule.
(4) Correct: F is the strongest oxidising agent (highest E ).
Answer: (1)