1 / 7

Understanding the Two-Step Termolecular Reaction Mechanism

Learn about a termolecular reaction involving NO and Br2, with a rate law indicating a two-step mechanism. The proposed reaction steps, equilibrium considerations, and how to determine [NOBr2] for the rate law are discussed.

ajaxe
Télécharger la présentation

Understanding the Two-Step Termolecular Reaction Mechanism

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Termolecular

  2. Fast Initial Step 2 NO (g) + Br2(g) 2 NOBr (g) • The rate law for this reaction is found to be Rate = k [NO]2 [Br2] • Because termolecular processes are rare, this rate law suggests a two-step mechanism.

  3. Step 1: NO + Br2 NOBr2 (fast) Fast Initial Step • A proposed mechanism is Step 2: NOBr2 + NO  2 NOBr (slow) Step 1 includes the forward and reverse reactions.

  4. Fast Initial Step • The rate of the overall reaction depends upon the rate of the slow step. • The rate law for that step would be Rate = k2 [NOBr2] [NO] • But how can we find [NOBr2]?

  5. Fast Initial Step • NOBr2 can react two ways: • With NO to form NOBr • By decomposition to reform NO and Br2 • The reactants and products of the first step are in equilibrium with each other. • Therefore, Ratef = Rater

  6. k1 k−1 [NO] [Br2] = [NOBr2] Fast Initial Step • Because Ratef = Rater , k1 [NO] [Br2] = k−1 [NOBr2] • Solving for [NOBr2] gives us

  7. k2k1 k−1 [NO] [Br2] [NO] Rate = Fast Initial Step Substituting this expression for [NOBr2] in the rate law for the rate-determining step gives = k [NO]2 [Br2]

More Related