MHT CET Medical202625 April 2026Evening ShiftChemistryChemical KineticsActual
The combination of NO ₂(g) and CO (g) occurs in two steps as follows: What is the rate law for the reaction? 2 NO ₂ NO + NO ₃(k₁) - slow NO ₃ + CO CO ₂ + NO ₂(k₂) - fast
Options
- ARate = k₂[ NO ₃][ CO ]
- BRate = k₁[ NO ₂]
- CRate = k₁[ NO ₂]^3
- DRate = k₁[ NO ₂]^2
Correct answer
D. Rate = k₁[ NO ₂]^2
Step-by-step solution
The rate of a complex reaction is determined by the slowest step, which is known as the rate-determining step. In the given mechanism, the first step is the slow step: 2 NO ₂ NO + NO ₃ For an elementary step, the rate law is written directly from its stoichiometry according to the law of mass action. Rate = k₁[ NO ₂]^2 Answer: Rate = k₁[ NO ₂]^2