The document discusses chemical kinetics and provides information about: - The factors that affect the speed of a chemical reaction, including concentration, temperature, and catalysts. - How to determine the rate law, rate constant, order, and mechanism of reactions from experimental data. - The relationship between concentration and time for reactions of different orders (zero, first, and second order). - How to calculate half-life, effect of temperature on reaction rate using the Arrhenius equation, and the role of homogeneous and heterogeneous catalysts.

1. Chemical KineticsStudy of speed with which a chemical reaction occurs and the factors affecting that speedProvides information about the feasibility of a chemical reactionProvides information about the time it takes for a chemical reaction to occurProvides information about the series of elementary steps which lead to the formation of product

2. Rate Data for A + B -> C

3. A + B -> CCAB

4. The Rate of a Chemical ReactionThe speed of a reaction can be examined by the decrease in reactants or the increase in products.a A + b B -> c C + d DWhere m and n are determined experimentally, and not necessarilyEqual to the stiochiometry of the reaction

5. Reaction A -> 2 BAABBBBABBBBAAABBBBAAABBBBABBBB2222=6.022 x 10 moleculesB6.022 x 10 molecules=Ain a 1.00 L containerin a 1.00 Liter container1 mol/L2 mol/L

6. Average RateRate of A disappearing isLet’s suppose that after 20 seconds ½ half of A disappears.Then And Rate of B appearing is Then

7. Average Rate Law for the General Equationa A + b B -> c C + d DFor Example:N2O5 (g) -> 2 NO2 (g) + ½ O2 (g)

8. Determination of the Rate EquationDetermined ExperimentallyCan be obtained by examining the initial rate after about 1% or 2% of the limiting reagent has been consumed.

9. Consider the Reaction:CH3CH2CH2CH2Cl (aq) + H2O (l) -> CH3CH2CH2CH2OH (aq) + HCl (aq)

10. Average Rates,

11. Average Rates,

12. Average Rates,

13. Average Rates,

14. Instantaneous Rate or initial rate at t=0 sInstantaneous Rate at t = 500 s

16. Order of ReactionZero order –independent of the concentration of the reactants, e.g, depends on lightFirst order - depends on a step in the mechanism that is unimolecularPseudo first order reaction – one of the reactants in the rate determining step is the solventSecond order – depends on a step in the mechanism that is bimolecularRarely third order – depends on the step in the mechanism that is termolecular

17. Data from the hydrolysis of n-butyl chloride

18. IF Zero Order

19. Therefore, the reaction is not zero order

20. If Second Order

21. Therefore, the reaction is not second order

22. IF First Order Reaction

23. First Order Plot

24. First Order Plot

25. Slope

26. Slope

27. Rate of the Reaction

28. For the ReactionN2O5 (g) -> 2 NO2 (g) + ½ O2 (g)The rate can be used to explain the mechanism

29. (1) Slow Step(2) Fast Step

30. Sum of the two steps:N2O5 -> 2 NO2 + ½ O2or2 N2O5 -> 4 NO2 + O2

31. ApplicationMechanism of a Chemical Reaction(a)Suggest a possible mechanism forNO2 (g) + CO (g) -> NO (g) + CO2 (g)Given that (b)Suggest a possible mechanism for2 NO2 (g) + F2 (g) -> 2 NO2F (g)Given that

32. Factors Affecting the Rate of a Chemical ReactionThe Physical State of MatterThe Concentration of the ReactantsTemperatureCatalyst

33. For A Reaction to OccurMolecules Must CollideMolecules must have the Appropriate OrientationMolecules must have sufficient energy to overcome the energy barrier to the reaction-Bonds must break and bonds must form

34. A Second Order Reaction

35. Rate Constant “k”Must be determined experimentallyIts value allows one to find the reaction rate for a new set of concentrations

36. The following data were collected for the rate of the reaction Between A and B, A + B -> C , at 25oC. Determine the rate law for the reaction and calculate k.

37. From Experiments 1 and 2Solution A:Divide equation (1) into equation (2)

38. Solution B:Subtract equation (2) from equation (1)

39. From Experiments 4 and 5Solution A:Divide equation (1) into equation (2)

40. Solution B:Subtract equation (2) from equation (1)

41. Rate Constant k

42. Rate Constant kFrom Experiment 3

43. Rate Constant kFrom Experiment 1

44. Your Understanding of this ProcessConsider the Data for the Following Reaction:Determine the Rate Law Expression and the value of k consistentWith these data.

45. From Experiments 1 and 2Solution :Divide equation (1) into equation (2)

46. From Experiments 2 and 3Solution :Divide equation (1) into equation (2)

47. Rate Expression

48. AssignmentDetermine the Rate Law for the following reaction from the given data:2 NO (g) + O2 (g) -> 2 NO2 (g)

49. Relationship Between Concentration and TimeFirst Order Reaction

50. A plot ofGives a Straight lineThe Following Reaction is a First Order Reaction:Plot the linear graph for concentration versus timeand obtain the rate constant for the reaction.

51. Data for the Transformation of cylcpropane to propene

52. slope = 2 x 10-5 s-1

53. Data for the Transformation of cylcpropane to propene

54. -slope = -2 x 10-5s-1Slope = 2 x 10-5 s-1

55. Relationship Between Concentration and TimeSecond Order Reaction

56. A plot ofGives a Straight lineThe Following Reaction is a Second Order Reaction:2 HI (g) -> H2 (g) + I2 (g)Plot the linear graph for concentration versus timeand obtain the rate constant for the reaction.

57. Data for the Transformation of hydrogen iodide gas to hydrogen and iodine

58. slope = 30. L mol-1 min-1

59. Graphical Method for Determining the Order of a ReactionFirst Order Reaction: y = ln (ao – x); x = t; slope = -k; and the intercept is lnao or y = ln (ao /(ao – x)); x = t; slope = k; and the intercept =0 Second Order Reaction: y = 1/ (ao – x); x = t; slope = k; and the intercept = 1/ aoZero Order Reaction: y = x; x = t; slope = k and the intercept = 0or y = ao – x ; x = t; slope = -k and the intercept = ao

60. Zero Order Reaction

61. Application of the Graphical Method for Determining the Order of a ReactionN2O5 (g) -> 2 NO2 (g) + ½ O2 (g)Tabulate the data so that each order may be tested

62. Data tabulation to determine which order will give a linear graph

63. Test for zero order reactionNot linear; therefore, the reaction is not zero order

64. Test for first order reactionLinear; therefore, the reaction is first order

65. Test for second order reactionNon-linear; therefore, the reaction is not second order

66. Half Life for a First Order Reaction

67. Half Life for a Second Order Reaction

68. Half Life for a Zero Order Reaction

69. Application of Half LifeThe rate constant for transforming cyclopropane into propene is 0.054 h-1Calculate the half-life of cyclopropane.Calculate the fraction of cyclopropane remaining after 18.0 hours.Calculate the fraction of cyclopropane remaining after 51.5 hours.

70. Half-LifeFraction of cyclopropaneRemaining after 18.0 hoursFraction of cyclopropaneRemaining after 51.5 hours

71. Effect of Temperature on the Reaction RateArrhenius Equation

72. Use the Following Data to Determine the Eactfor

74. Effect of a Catalyst on the Rate of a ReactionLowers the energy barrier to the reaction via lowering the energy of activationHomogeneous catalyst- in the same phase as the reacting moleculesHerterogeneous catalyst – in a different phase from the reacting molecules

75. Example of a Homogeneous Catalyst

77. Example of Heterogeneous Catalyst

78. An interesting problem:The reaction between propionaldehyde and hydrocyanic acid have been observed by Svirbely and Roth and reported in the Journal of the American Chemical Society. Use this data to ascertain the order of the reaction and the value of the rate constant for this reaction.

80. Check to determine first order in HCN

81. Check to determine first order in propionaldehyde

82. So close; therefore, let’s take another approach. Let [HCN] = ao and [propionaldehyde] = boThen,

85. Let’s construct the data in a different format

86. Slope = 0.678; therefore, k = 0.678 M-1min-1

87. Mechanism:

88. Steps 1 and 2 are fast equilibrium steps; and step 3 is the rate determining step

91. Revisit the kinetics for2 NO (g) + O2 (g) -> 2 NO2 (g)