Question

Identify the incorrect statement from the following:

• A. The acidic strength of HX (X = F, Cl, Br and I) follows the order: HF > HCl > HBr > HI.
• B. Fluorine exhibits –1 oxidation state whereas other halogens exhibit +1, +3, +5 and +7 oxidation states also.
• C. The enthalpy of dissociation of F2 is smaller than that of Cl2.
• D. Fluorine is stronger oxidising agent than chlorine.

Answer 1

Answer: (A)

The acidic strength of HX (X = F, Cl, Br and I) follows the order: HF > HCl > HBr > HI.

Answer 2

The acidic strength of the hydrogen halides (HX) increases down the group: $HF < HCl < HBr < HI$. This trend is due to the decreasing bond strength of the H-X bond as the size of the halogen atom increases. The weaker the bond, the more readily the hydrogen ion (H+) can dissociate, resulting in a stronger acid. Thus, statement (1) is incorrect.

The other statements are correct:

• Fluorine is the most electronegative element and only exhibits a -1 oxidation state. Other halogens can exhibit multiple oxidation states (+1, +3, +5, and +7).
• The bond dissociation enthalpy of F2 is smaller than that of Cl2 due to the high electron-electron repulsion between the lone pairs in the small fluorine molecule.
• Fluorine is a stronger oxidizing agent than chlorine due to its higher electronegativity and smaller size.