1. Kinetics Chapter 15

2. Introduction Rate of Reaction – the rate at which ________ are ___________ and __________ are ______________. Chemical Kinetics – the study of the ____________ of ______________.

3. Ways to Detect Concentration Titrations – (Quenching) Spectrophotometer -

4. Factors that affect Reaction Rates Nature of the Reactants – Concentration – Temperature – Presence of a Catalyst –

5. Rate = k[A] x [B] y Zero order – the concentration of the reactant _________ affect the rate of production of product. The concentration of reactant is doubled, the rate of production of product __________________. First order – the concentration of the reactant _________ affect the rate of production of product. The concentration of reactant is doubled, the rate of production of product __________________.

6. Second order – the concentration of the reactant _________ affect the rate of production of product. The concentration of reactant is doubled, the rate of production of product __________________. Overall order =

7. Example 1 Expt[A][B]Rate (M/sec) 11.0 x10 -2 1.0 x 10 -2 1.5 x 10 -6 21.0 x 10 -2 2.0 x 10 -2 3.0 x 10 -6 32.0 x 10 -2 1.0 x 10 -2 6.0 x 10 -6

8. Example 2 Expt[A][B][C]Rate(M/min) 1.20.20.202.4 x 10 -6 2.40.30.209.6 x 10 -6 3.20.30.202.4 x 10 -6 4.20.40.607.2 x 10 -6

9. Example 3 Expt[A][B]Rate (M/min) 1.01.016.00 x 10 -3 2.02.031.44 x 10 -1 3.01.021.20 x 10 -2

10. CLR Graphs Concentration vs Time ln of Concentration vs Time Reciprocal of Concentration vs Time

11. First Order Reactions ln([A] 0 /[A]) = akt A 0 = Initial Concentration A = Concentration at some point a = Coefficient of A k = Rate Constant t = Time

12. Half Life of a First Order Rxn t 1/2 = ln2/ak

13. Compound A decomposes to form B and C in a reaction that is first order with respect to A and first order overall. At 25C, the specific rate constant for the reaction is 0.0450 sec -1. What is the half life of A? A  B + C

14. The reaction 2N 2 O 5  2N 2 O 4 + O 2 obeys the rate law: rate = k[N 2 O 5 ], in which the specific rate constant is 0.00840 sec -1 at a certain temperature. If 2.50 moles of N 2 O 5 were placed in a 5.00 Liter container at that temperature, how many moles of N 2 O 5 would remain after 1.00 minutes? How long would it take for 90% of the original N 2 O 5 to react?

15. Second Order Rxn 1/[A] - 1/[A] 0 = akt t 1/2 = 1/(ak[A] 0 ) Compounds A and B react to form C and D in a reaction that was found to be second order in A and second order overall. The rate constant is 0.622 liters per mole per minute. What is the half life of A when 4.10 x 10 -2 M A is mixed with excess B.

16. The gas phase decomposition of NOBr is second order in [NOBr] with k = 0.810 M -1 sec -1 at 10C. We start with 4.00 x 10 -3 M NOBr in a flask at 10C. How many seconds does it take to use up 1.50 x 10 -3 M of this NOBr? 2NOBr  2 NO + Br 2

17. Consider the reaction in the previous problem. If we start with 2.40 x 10 -3 M NOB, what concentration of NOBr will remain after 5.00 minutes of reaction?

18. Zero Order Rxn Rate = -1/a(  [A]/  t) = k t 1/2 = [A] 0 /2ak

19. http://genchem1.chem.okstate.edu/C CLI/Startup.html

20. Collision Theory of Reaction Rates In order for a reaction to occur the molecules, atoms, or ions must ______________. In order for the collision to be successful the reactants must – A. – B. How does the presence of a Catalyst help with this?

21. The Transition State Activation Energy

22. Rate Determining Step A reaction can never proceed faster than its ____________ step. Most reactions occur not in one step, but instead in several smaller steps that include fast moving steps as well as slow moving steps.

23. Example 1 NO 2 + NO 2  N 2 O 4 (Slow) N 2 O 4 + CO  NO + CO 2 + NO 2 (Fast) What are the intermediates? What is the rate law for this reaction?

24. Example 2 NO + Br 2  NOBr 2 (fast) NOBr 2 + NO  2NOBr (slow) What are the intermediates? What is the rate law for this reaction?

25. Example 3 I 2  2I (fast) I + H 2  H 2 I (fast) H 2 I + I  2HI (slow) What are the intermediates? What is the rate law for this reaction?

26. Temperature and Reactions As the temperature goes up __________ molecules have the energy required. Arrheius Equation – k = Ae -Ea/RT – ln k = lnA – E a /RT A is a constant that is equal to the # of collisions R = 8.314 As Ea goes up what happens to reaction speed? As T goes up, what happens to reaction speed?

27. ln (k 2 /k 1 ) = Ea/R x (1/T 1 – 1/T 2 ) The specific rate constant, k, for the following first order reaction is 9.16 x 10 -3 sec -1 at 0C. The activation energy of this reaction is 88.0 kJ/mol. Determine the value of k at 2.0C. N 2 O 5  NO 2 + NO 3

28. The gas phase decomposition of ethyl iodide to give ethylene and hydrogen iodide is a first order reaction. At 600K, the value of k is 1.60 x 10 -5 sec -1. When the temperature is raised to 700K, the value of k increases to 6.36 x 10 -3 sec -1. What is the activation energy for this reaction?

29. Catalyst Homogeneous Catalyst Heterogeneous Catalyst Enzymes – Substrates