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MHT CET202619 April 2026Morning ShiftChemistryChemical KineticsActual

Which of the following is an elementary reaction ?

Options

  1. AO _ 3(g) O _ 2(g) + O _ (g)
  2. B2 NO ₂ Cl _ (g) 2 NO _ 2(g) + Cl _ 2(g)
  3. C2 NO _ 2(g) + F _ 2(g) 2 NO ₂ F _ (g)
  4. D2 NO _ (g) + Cl _ 2(g) 2 NOCl _ (g)

Correct answer

A. O _ 3(g) O _ 2(g) + O _ (g)

Step-by-step solution

An elementary reaction is one that occurs in a single step and has a single transition state. The decomposition of ozone, O _ 3(g) O _ 2(g) + O _ (g) , is a unimolecular elementary reaction. The other reactions are complex and occur in multiple steps: 2 NO ₂ Cl _ (g) 2 NO _ 2(g) + Cl _ 2(g) occurs via: NO ₂ Cl NO ₂ + Cl (slow) NO ₂ Cl + Cl NO ₂ + Cl ₂ (fast) 2 NO _ 2(g) + F _ 2(g) 2 NO ₂ F _ (g) occurs via: NO ₂ + F ₂ NO ₂ F + F (slow) NO ₂ + F NO ₂ F (fast) 2 NO _ (g) + Cl _ 2(g) 2 NOCl _ (g) occurs via: NO + Cl ₂

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