MHT CET Chemistry Question (2026) — Solution

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: Step 1: NO _2 Cl NO _2 + Cl (slow) Step 2: NO _2 Cl + Cl NO _2 + Cl _2 (fast) 2 NO _ 2(g) + F _ 2(g) 2 NO _2 F _ (g) occurs via: Step 1: NO _2 + F _2 NO _2 F + F (slow) Step 2: NO _2 + F NO _2 F (fast) 2 NO _ (g) + Cl _ 2(g) 2 NOCl _ (g) occurs via: Step 1: NO + Cl _2 NOCl _2 (fast) Step 2: NOCl _2 + NO 2 NOCl (slow) Therefore, only the first reaction is elementary. Answer: O _ 3(g) O _ 2(g) + O _ (g)