Question of the Day

1. Question of the Day Day 4 3-25 The data in the table below were obtained for the rxn: 2 a. The order of the reaction in A is ____. b. The order of the reaction in B is ____. c. The overall order of the reaction is ____. 0 2

2. Objective Day 4 3-25 How fast / slow do reactions go?

3. Rxn Mechanisms & Rate-Determining Steps A. A reaction mechanism is a series of ____________ that lead to a net reaction. B. Reaction mechanisms can have _____________ steps. C. Parts of mechanisms 1. Net reaction is _________ simple rxns one or more the goal

4. Rxn Mechanisms & Rate-Determining Steps C. Parts of mechanisms 1. Net reaction is __________ 2. Elementary step is one of the __________ in the ________ 3. Intermediate product is a product that is made by _______________ _____ that becomes a _________ in a subsequent ________________ the goal reactions process an elementary step reactant elementary step

5. Rxn Mechanisms & Rate-Determining Steps C. Parts of mechanisms 4. Catalyst is a substance that first appears as a _________ in one ________________ and then becomes a ________ in a subsequent ________________ reactant elementary step product elementary step

6. Rxn Mechanisms & Rate-Determining Steps Reaction mechanisms that have multiple steps have one step that is the rate-determining step. The rate-determining step is the step that is the _______ of all the steps. slowest

7. http://wps.prenhall.com/esm_brown_chemistry_9/2/660/169060.cw/index.htmlhttp://wps.prenhall.com/esm_brown_chemistry_9/2/660/169060.cw/index.html Homework # 2 Chapter 14 – w/ discussion partner – show me successful screen (100%) # 7 = the reaction rate would quadruple.  doubling the partial pressure is the same as doubling the concentration. Period 1 3-22

8. Question of the Day Day 5 3-26 Suppose that for the reaction A + B → C, the rate law is rate = 3.0 x 10-5 [A][B]2. What is the concentration of “B” if [A] = 0.10 M and the rate is 1.2 x 10-11M/s? There are no units on k, what should they be? 0.002 M

9. Lab Reports – Results + Calculations sections

10. Rxn Mechanisms & Rate-Determining Steps E. Write several mechanisms and identify any intermediates and catalysts. 1. 1-step mechanism for reaction of calcium oxide with water

11. Rxn Mechanisms & Rate-Determining Steps E. Write several mechanisms and identify any intermediates and catalysts. 2. 2-step mechanism for rxn of NO2 with CO to produce NO and CO2 (all gases) NO2 + NO2 NO3 + NO slow NO3 + CO  NO2 + CO2 fast NO2 + CO  NO + CO2 net

12. Rxn Mechanisms & Rate-Determining Steps 2. 2-step mechanism for rxn of NO2 with CO to produce NO and CO2 (all gases) NO2 + NO2 NO3 + NO slow NO3 + CO  NO2 + CO2 fast NO2 + CO  NO + CO2 net Intermediate = NO3

13. Rxn Mechanisms & Rate-Determining Steps E. Write several mechanisms and identify any intermediates and catalysts. 3. 3-step mechanism for the rxn of HBr with O2 to produce H2O and Br2 (all gases) HBr + O2 HOOBr HBr + HOOBr  2 HOBr 2 HBr + 2 HOBr  2 H2O + 4 Br2 4 HBr + O2 2 H2O + 4 Br2

14. Rxn Mechanisms & Rate-Determining Steps 3. 3-step mechanism for the rxn of HBr with O2 to produce H2O and Br2 (all gases) HBr + O2 HOOBr HBr + HOOBr  2 HOBr 2 HBr + 2 HOBr  2 H2O + 4 Br2 4 HBr + O2 2 H2O + 4 Br2 Intermediates = HOOBr and HOBr

15. Rxn Mechanisms & Rate-Determining Steps 4. Write the net rxn for the following 2-step mechanism. NO2(g) + SO2(g) → NO(g) + SO3(g) 2 NO(g) + O2(g) → 2 NO2(g)

16. Assignment: Review section 18.2 and complete #s 9-16 on page 608.

17. LAB

18. LABS: Presentations: Alex and Kagiso Adam and Riley *** we are presenting on Thursday 3-8 Lab packets are due for everyone else on Wednesday 3-7.

19. Question of the Day Day 3 3-7 Describe how intermediates, activated complexes, and catalysts are different (thoroughly!).

20. Question of the Day Day 4 3-8 The rate constant is 4.17 x 10-5 s-1 for the first order decomposition of ethyl chloride, C2H5Cl, at 700 K. The original concentration was 2.00 M. a. Find the concentration of C2H5Cl after one hour. b. Calculate the time needed for the concentration of C2H5Cl to decrease to half of its original value.

21. Review Day 4 3-8 Analyze the following reaction mechanism: step 1: N2O  N2 + O step 2: N2O + O  N2 + O2 What is the net reaction? Are there any intermediates and/or catalysts present? Which step do you think is rate determining? WHY?

22. Equilibrium Equilibrium occurs when the forward and reverse reactions occur at equal rates – NOT a standstill!

23. Equilibrium A. Physical Equilibrium Example 1. H2O(l)⇄ H2O(g) 2. Appearance of system Rate of Evap. = Rate of Cond. To regular eyes: Looks as if nothing is happening But on the molecular level: 2 rxns or Ds occur simultaneously

24. Equilibrium B. Chemical Reaction Options 1. Rxn goes to completion  products stay & reaction stops; Ex : burning 2. No go : He + Ne  no rxn 3. Rxn reaches equilibrium = get a set amount of reactants & products coexisting C. Main Concern of Equilibrium Calculations 1.How FAR will the reaction go? 2. How much product can be made?

25. Equilibrium D. What conditions must be met to attain equilibrium? • Constant T & P • Closed container • DG = 0

26. Equilibrium E. Example equilibrium system and experimental data: 2 HI(g) ⇄ I2(g) + H2(g) 0.16 0.02 0.02 0.16 0.02 0.02 0.24 0.03 0.03

27. Equilibrium • What happened to the concentrations of each substance during the experiments? • Exp #1 & #2 • Changed to form chemicals not present at the start of the reaction • Exp #3 • Changed to form more of the “favored” chemicals

28. Equilibrium C. Example of system reaching equilibrium N2O4(g) ⇄ 2 NO2(g) at 100 °C