CHM135H1 Lecture Notes - Lecture 16: Reaction Step, Elementary Reaction, Rate Equation

96 views6 pages

Verified Note

limerhinoceros188

13 Oct 2018

School

UTSG

Department

Chemistry

Course

CHM135H1

Professor

Gilbert Walker, Eugenia Kumacheva, Kristine Quinlan

For unlimited access to Class Notes, a Class+ subscription is required.

CHM135H1 verified notes

16/38View all

CHM135H1 Lecture 15: CHM135, Lecture 15 Tues Oct 9 2018

CHM135H1 Lecture Notes - Lecture 16: Reaction Step, Elementary Reaction, Rate Equation

CHM135H1 Lecture Notes - Lecture 17: Rate Equation, Partial Pressure, Clinical Toxicology

Document Summary

October 12, 2018 (relevant reading: chemistry 2nd ed. Why is it useful: better understanding better control, e. g. if we understand the causes of global warming, we can take action to slow it down. How are the molecules reacting: rate = k[a][b] Molecular level of understanding: dependence on concentration suggests how a reaction occurs the mechanism. Reaction mechanism a sequence of elementary steps (or elementary reactions) which add up to give the overall (net) reaction; the sequence of reaction steps that shows the pathway from reactants to products. Reaction: 2no(g) + o2 (g) 2no2 (g: here are 2 elementary steps for an overall reaction, no(g) + no(g) n2o2 (g, n2o2 (g) + o2 (g) 2no2 (g) = 2no(g) + o2 (g) 2no2 (g) Net reaction: sum of 2 elementary steps. N2o2 is a reaction intermediate (formed and used up in the reaction). It does not appear in the overall reaction; it"s included in rate laws of elementary steps.

Related Questions

PLEASE EXPLAIN ALL OF THIS BETTER THAN THE BOOK AND DO EXAMPLE 14.9!!!

Ozone naturally decomposes to oxygen by this reaction: 2 O_3 (g) rightarrow 3 O_2 (g) The experimentally observed rate law for this reaction is: Rate = k [O_3]^2 [O_2]^-1 Show that this proposed mechanism is consistent with the experimentally observed rate law. O_3 (g) O_2 (g) + O (g) Fast O_3 (g) + O(g) 2 O_2 (g) Slow To determine whether the mechanism is valid, you must First determine whether the steps sum to the overall reaction. The steps do indeed sum to the overall reaction, so the first condition is met. O_3 (g) O_2 (g) + O (g) O_3 (g) + O (g) 2 O_2 (g)/2 O_3 (g) rightarrow 3 O_2 (g) The second condition is that the rate law predicted by the mechanism is consistent with the experimentally observed rate law. Because the second step is rate limiting, write the rate law based on the second step. Rate = k_2 [O_3] [O] Because the rate law contains an intermediate (O), you must express the concentration of the intermediate in terms of the concentrations of the reactants of the overall reaction. To do this, set the rates of the forward reaction and the reverse reaction of the first step equal to each other. Solve the expression from the previous step for [O], the concentration of the intermediate. Rate (forward) = Rate (backward) k_1 [O_3] = k_-1 [O_2] [O] [O] = k_1 [O_3]/k_-1 [O_2] Finally, substitute [O] into the rate law predicted by the slow step. Rate = k_2 [O_3] [O] = k_2 [O_3] k_1 [O_3]/k_-1 [O_2] = k_2 k_1 [O_3]^2/k_-1 [O_2] = k [O_3]^2 [O_2]^-1 CHECK Because the two steps in the proposed mechanism sum to the overall reaction, and because the rate law obtained from the proposed mechanism is consistent with the experimentally observed rate law, the proposed mechanism is valid. The -1 reaction order with respect to [02J indicates that the rate slows down as the concentration of oxygen increases- oxygen inhibits, or slows down, the reaction. FOR PRACTICE 14.9 Predict the overall reaction and rate law that results from the following two-step mechanism: 2 A rightarrow A_2 Slow A_2 + B rightarrow A_2 B Fast

CHM135H1 Lecture Notes - Lecture 16: Reaction Step, Elementary Reaction, Rate Equation

CHM135H1 Lecture 15: CHM135, Lecture 15 Tues Oct 9 2018

CHM135H1 Lecture Notes - Lecture 16: Reaction Step, Elementary Reaction, Rate Equation

CHM135H1 Lecture Notes - Lecture 17: Rate Equation, Partial Pressure, Clinical Toxicology

Document Summary

Get access

Related Documents

CHM135H1 Lecture Notes - Lecture 15: Hydrogen Iodide, Joule, Activated Complex

CHM135H1 Chapter Notes - Chapter 13: Reaction Step, Reaction Intermediate, Reaction Rate

CHM135H1 Lecture Notes - Lecture 15: Elementary Reaction, Arrhenius Equation, Reaction Step

Related Questions