Question
What is the order and molecularity of the following elementary reaction? 2 NO _ 2(g) 2 NO _ (g) + O _ 2(g) , rate = k [ NO _2]^2
MHT CET
Chemistry
Chemical Kinetics
2026
MHT CET 2026 (20 April Shift 2)
MHT CET Chemistry Question (2026) — Solution
Options
- A. The reaction is second order and biomolecular.
- B. The reaction is first order and bimolecular.
- C. The reaction is second order and unimolecular.
- D. The reaction is zero order and unimolecular.
Answer
A. The reaction is second order and biomolecular.
Step-by-step solution
For an elementary reaction, the rate law is determined by its stoichiometry. Given rate = k[ NO _2]^2 The order of the reaction is the sum of the exponents of the concentration terms in the rate law. Here, the exponent is 2, so the order is 2. The molecularity of an elementary reaction is the number of reactant molecules participating in the reaction. Since 2 molecules of NO _2 are reacting, the molecularity is 2 (bimolecular). Thus, the reaction is second order and bimolecular. Answer: The reaction is second order and biomolecular.
Related: Chemistry — Chemical Kinetics · All PYQ Banks