Question

For reaction NO2 + CO→NO + CO2 takes place in 2 steps
(1) NO2 + NO2 → NO3 + NO (slow)
(2) NO3 + CO →NO2 + CO2 (fast)
Q.1 write rate law
Q.2 what is role of NO3

Answer 1

Q1. Rate law for the reaction:

$$ν=k×[NO_2]×[CO]$$

Rate law for the first step:

$$v_1=k_1×[NO_2]^2$$

Rate law for the second step:

$$v_2= k_2×[NO_3]×[CO]$$

Q2. $NO_3$ plays the role if catalyst which speeds up the rection. A catalyst forms transition complex with reactants thus decreasing the activation energy, required for the reaction to procced. As less energy is required the reaction proceeds faster.