1 / 15

Reaction Mechanics

Reaction Mechanics. Explain the concept of a reaction mechanism . Include: rate determining step , potential energy diagrams. Additional KEY Terms Bimolecular Intermediate. 2 NO ( g ) + O 2 ( g ) 2 NO 2 ( g ). For this reaction to occur in one step ,

violet
Download Presentation

Reaction Mechanics

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. Reaction Mechanics

  2. Explainthe concept of a reaction mechanism. • Include: rate determining step, potential energy diagrams Additional KEY Terms Bimolecular Intermediate

  3. 2 NO (g) + O2 (g) 2 NO2 (g) For this reaction to occur in one step, 3 particles must collide - at exactly the same time with the correct orientation and enough energy. Three particle collisions are quite rare.

  4. 2 NO (g) + O2 (g) 2 NO2 (g) Reactions take place in steps. Each step involves a collision between two particles, or bimolecular. Simple reaction - take place in one elementary step. Multiple steps – complex reactions.

  5. 2 NO (g) + O2 (g) 2 NO2 (g) N2O2 - is called a reaction intermediate. (product in one step then reactant in another) Do not confuse with Activated Complex

  6. The steps in which a reaction occurs is called the reaction's mechanism. Sum of the steps of a mechanism equals the total or net equation.

  7. 2 O3 (g) 3 O2 (g) Decomposition of ozone, with a chlorine catalyst. 1: Cl2 + O3 ClO + O2 2: O3 O2 + O 3: ClO + O Cl2 + O2 Cl2– catalyst ClO and O– intermediates Neither is included in the NetReaction.

  8. Rate Determining Step Not all steps in a mechanism have the same rate. The step with the slowest rate is called the rate determining step (RDS). The RDS determines the overall reaction rate. RDS usually has the greatest EA.

  9. RDS has the greatest affect on the overall rate. Changes to the reactants in the other steps will have very little effect on the overall rate.

  10. endothermic exothermic -ΔH overall

  11. 1. B + B E fastendothermic 2. E + A C slowendothermic A + 2B C + ΔH PE (kJ)

  12. - ΔH overall P + Q X + T (slow, endo) X + P Y + R (fast, exo) Y + S T (moderate, exo) a) What is the net reaction? a) 2P + Q + S  2T + R b) What are the reaction intermediates? b) X + Y c) Which is the rate determining step? c) First Step d) What would be the effect of increasing [P]? d) Increases the overall rate e) What would be the effect of decreasing [Q]? e) Decreases the overall rate f) What would be the effect of increasing [S]? f) No significant overall change in rate g) What would a PE graph look like for this reaction?

  13. - ΔH overall P + Q X + T (slow, endo) X + P Y + R (fast, exo) Y + S T (moderate, exo) g) What would a PE graph look like for this reaction? PE (kJ)

  14. Most reactions occur in several steps. • Each step is usually bimolecular. • Sum of these steps must equal the net equation. • Mechanism for a reaction can only be determined experimentally. • Rate determining step is the slowest step and affects the rate of the reaction the most.

  15. CAN YOU / HAVE YOU? • Explainthe concept of a reaction mechanism. • Include: rate determining step, potential energy diagrams Additional KEY Terms Bimolecular Intermediate

More Related