Question

Which one of the following is an incorrect statement?

• A. O\textsubscript{3} oxidises PbS to PbSO\textsubscript{4}
• B. O\textsubscript{3} oxidises nitric oxide to nitrogen dioxide
• C. O\textsubscript{3} oxidises aqueous KI at pH = 9.2
• D. The two oxygen–oxygen bond lengths in O\textsubscript{3} are different
• E. O\textsubscript{3} is used as an oxidizing agent in the manufacture of KMnO\textsubscript{4}

Hint:

Whenever a molecule has resonance (like $O_3$, $Benzene$, or $CO_3^{2-}$), the bond lengths are always equalized. Look for resonance to debunk claims of unequal bond lengths!

Answer 1

The Correct Option is D

Concept: Ozone (O\textsubscript{3}) is an allotrope of oxygen with a bent molecular geometry and strong oxidizing properties.
• Resonance: Ozone exists as a resonance hybrid of two equivalent Lewis structures.
• Bonding: Due to resonance, the bond order between the oxygen atoms is approximately 1.5, making both bonds identical in character and length.
• Oxidizing Action: Ozone readily liberates nascent oxygen ($O_3 \rightarrow O_2 + [O]$), making it a powerful oxidant.

Step 1: Analyze the structural symmetry of Ozone. In the ozone molecule, the central oxygen atom is bonded to two terminal oxygen atoms. Resonance delocalizes the double bond across both positions. Experimental data shows that both O—O bond lengths are exactly equal (128 pm). Therefore, the claim that they are "different" is incorrect.

Step 2: Review chemical reactions of Ozone. - (A) $PbS + 4O_3 \rightarrow PbSO_4 + 4O_2$ (True) - (B) $NO + O_3 \rightarrow NO_2 + O_2$ (True) - (C) Ozone reacts with KI in a borate buffer (pH 9.2) to liberate Iodine. (True) - (E) Ozone can oxidize manganate ($MnO_4^{2-}$) to permanganate ($MnO_4^-$). (True)