Exercise 7 | Chemical Kinetics: Mechanisms
Here is a reaction: 2 NO (g) + Cl2 (g) → 2 NOCl (g).
The rate of this reaction is k [NO]2[Cl2].
Is the following mechanism plausible for this reaction?
NO (g) + Cl2 (g) NOCl (g) + Cl (g) (fast, equilibrium)
NO (g) + Cl(g) → NOCl (g) (slow)
Let’s determine the rate of the reaction if the mechanism is correct:
rate of the reaction = rate of the slow step = k[NO][Cl]
First step: fast equilibrium: k1 [NO][Cl2] = k-1 [NOCl][Cl]
⇒ [Cl] = k1 [NO][Cl2] / k-1 [NOCl] = K [NO][Cl2]/ [NOCl]
rate of the reaction = k[NO][Cl] = k’ [NO]2[Cl2]/[NOCl]
⇒ The mechanism is not plausible