MHTCET 13 Apr 2026 Shift 2 Paper

Concept:Resonance in ozone equalises both $\mathrm{O}-\mathrm{O}$ bonds, giving a bond length intermediate between a single and a double bond.Explanation:Ozone, $\mathrm{O}_3$, is represented by two resonating structures:$$\mathrm{O}=\mathrm{O}-\mathrm{O} \leftrightarrow \mathrm{O}-\mathrm{O}=\mathrm{O}$$Due to resonance, both $\mathrm{O}-\mathrm{O}$ bonds are identical and possess partial double-bond character.A typical $\mathrm{O}-\mathrm{O}$ single bond length is about $148$ pm, while an $\mathrm{O}=\mathrm{O}$ double bond is about $121$ pm.The actual $\mathrm{O}-\mathrm{O}$ bond length in ozone lies between these two values because of resonance.The experimentally observed bond length is $128$ pm, which matches option B.Answer:The $\mathrm{O}-\mathrm{O}$ bond length in ozone is $128$ pm.Correct option: B. 128 pm