Physical Chemistry 3: — Chemical Kinetics — - Christian-Albrechts ...

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3.2 Application of the steady-state assumption 45 3.2.2 Further examples I I Exercise 3.1: The thermal decomposition of acetaldehyde according to the overall reaction CH 3 CHO → CH 4 +CO (3.31) is known to proceed via the following elementary steps (Rice-Herzfeld mechanism): CH 3 CHO → CH 3 +HCO (1) CH 3 +CH 3 CHO → CH 4 +CH 3 CO (2) (3.32) CH 3 CO → CH 3 +CO (3) CH 3 +CH 3 → C 2 H 6 (4) Derive an expression for the production rate of [CH 4 ]. (Hint: Use the steady-state approximations for [CH 3 CO] and [CH 3 ] and neglect the HCO for the derivation of the expression.) ¤ A more complete mechanism takes into account the thermal decomposition of the HCO radicals according to HCO → H + CO (5) followed by the reaction H + CH 3 CHO → H 2 +CH 3 CO (6). Solution 3.1: With the steady state approximations for [CH 3 CO] and [CH 3 ],weobtain [CH 3 CO] = 2 [CH 3 ][CH 3 CHO] − 3 [CH 3 CO] ≈ 0 (3.33) y [CH 3 CO] = 2 [CH 3 ][CH 3 CHO] 3 (3.34) and y [CH 3 ] = 1 [CH 3 CHO] − 2 [CH 3 ][CH 3 CHO] (3.35) + 3 [CH 3 CO] − 2 4 [CH 3 ] 2 (3.36) = 1 [CH 3 CHO] − 2 [CH 3 ][CH 3 CHO] (3.37) + 3 2 [CH 3 ][CH 3 CHO] − 2 4 [CH 3 ] 2 3 (3.38) = 1 [CH 3 CHO] − 2 4 [CH 3 ] 2 ≈ 0 (3.39) µ 12 1 [CH 3 CHO] y [CH 3 ] = (3.40) 2 4 [CH 4 ] [CH 4 ] = 2 [CH 3 ][CH 3 CHO] = 2 µ 1 2 4 [CH 3 CHO] 32 (3.41) ¥ I Exercise 3.2: The thermal decomposition of ethane gives mainly H 2 +C 2 H 4 . In addition, small amounts of CH 4 are formed. The decay of the C 2 H 6 concentration can be described by the reaction steps C 2 H 6 → CH 3 +CH 3 (1) CH 3 +C 2 H 6 → CH 4 +C 2 H 5 (2) C 2 H 5 → C 2 H 4 +H (3) (3.42) H+C 2 H 6 → C 2 H 5 +H 2 (4) H+C 2 H 5 → C 2 H 6 (5)
3.2 Application of the steady-state assumption 46 Using the steady-state approximations for the radicals [CH 3 ], [C 2 H 5 ],and[H], derivea rate law describing the overall decay of [C 2 H 6 ]. Note: From the C-H bond dissociation energies in C 2 H 6 and C 2 H 5 ,itisknownthat 3 À 1 . ¤ I Solution 3.2: − [C 2H 6 ] = " µ 3 2 2 1 + 1 4 + 12 # 1 3 4 [C 2 H 6 ] (3.43) 5 ¥
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Physical Chemistry 3: — Chemical
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iii 2.7 Temperature dependence of r
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v 7.1.2 Formal kinetic model 149 7.
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vii 12 Photochemical reactions 241
Page 9 and 10: ix Preface This scriptum contains l
Page 11 and 12: xi Disclaimer Use of this text is e
Page 13 and 14: xiii I Figure 2: Organisational mat
Page 15 and 16: xv I Figure 6: Recommended textbook
Page 17 and 18: 1.2 Time scales for chemical reacti
Page 19 and 20: 1.2 Time scales for chemical reacti
Page 21 and 22: 1.3 Historical events 6 I Empirical
Page 23 and 24: 1.4 References 8 2. Formal kinetics
Page 25 and 26: 2.1 Definitions and conventions 10
Page 31 and 32: 2.2 Kinetics of irreversible first-
Page 33 and 34: 2.2 Kinetics of irreversible first-
Page 35 and 36: 2.3 Kinetics of reversible first-or
Page 37 and 38: 2.3 Kinetics of reversible first-or
Page 39 and 40: 2.4 Kinetics of second-order reacti
Page 41 and 42: 2.4 Kinetics of second-order reacti
Page 43 and 44: 2.5 Kinetics of third-order reactio
Page 45 and 46: 2.6 Kinetics of simple composite re
Page 51 and 52: 2.7 Temperature dependence of rate
Page 57 and 58: 3.1 Determination of the order of a
Page 59: 3.2 Application of the steady-state
Page 63 and 64: 3.4 Generalized first-order kinetic
Page 73 and 74: 3.5 Numerical integration 58 I Surv
Page 75 and 76: 3.5 Numerical integration 60 2 ord
Page 77 and 78: 3.5 Numerical integration 62 3.5.5
Page 79 and 80: 3.5 Numerical integration 64 , Func
Page 81 and 82: 3.6 Oscillating reactions* 66 3.6 O
Page 83 and 84: 3.6 Oscillating reactions* 68 • B
Page 85 and 86: 3.6 Oscillating reactions* 70 (5) S
Page 87 and 88: 3.6 Oscillating reactions* 72 I Fig
Page 89 and 90: 3.6 Oscillating reactions* 74 [X]
Page 91 and 92: 3.7 References 76 4. Experimental m
Page 93 and 94: 4.3 The discharge flow (DF) techniq
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Page 97 and 98: 4.4 Flash photolysis (FP) 82 4.4 Fl
Page 99 and 100: 4.4 Flash photolysis (FP) 84 I Figu
Page 101 and 102: 4.6 Stopped flow studies 86 4.6 Sto
Page 103 and 104: 4.8 Relaxation methods 88 4.8 Relax
Page 105 and 106: 4.9 Femtosecond spectroscopy 90 I F
Page 107 and 108: 4.9 Femtosecond spectroscopy 92 I F
Page 109 and 110: 4.10 References 94 5. Collision the
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5.1 Hardspherecollisiontheory 96
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5.1 Hardspherecollisiontheory 98 I
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5.1 Hard sphere collision theory 10
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5.2 Kinetic gas theory 102 I The 1D
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5.2 Kinetic gas theory 104 I Figure
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5.2 Kinetic gas theory 106 5.2.2 Th
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5.2 Kinetic gas theory 108 • Resu
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5.3 Transport processes in gases 11
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5.4 Advanced collision theory 116 W
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5.4 Advanced collision theory 118 I
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5.4 Advanced collision theory 120 5
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5.4 Advanced collision theory 126 a
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5.4 Advanced collision theory 130 (
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5.4 Advanced collision theory 136
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5.4 Advanced collision theory 138 6
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6.2 Polyatomic molecules 140 I Figu
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6.2 Polyatomic molecules 142 I Mode
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6.3 Trajectory Calculations 144 •
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6.3 Trajectory Calculations 146 7.
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7.1 Foundations of transition state
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7.2 Applications of transition stat
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7.3 Thermodynamic interpretation of
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7.4 Transition state spectroscopy 1
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8.1 Experimental observations 176 (
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8.2 Lindemann mechanism 178 8.2 Lin
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8.2 Lindemann mechanism 180 I Half-
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8.3 Generalized Lindemann-Hinshelwo
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8.4 The specific unimolecular react
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8.5 Collisional energy transfer* 20
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8.6 Recombination reactions 202 8.7
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9.1 Chain reactions and chain explo
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9.1 Chain reactions and chain explo
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9.2 Heat explosions 208 • positiv
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9.2 Heat explosions 210 (3) We can
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9.2 Heat explosions 212 9.2.3 Explo
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9.2 Heat explosions 214 10. Catalys
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10.1 Kinetics of enzyme catalyzed r
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10.2 Kinetics of heterogeneous reac
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11.1 Qualitative model of liquid ph
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11.2 Diffusion-controlled reactions
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11.2 Diffusion-controlled reactions
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11.3 Activation controlled reaction
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11.4 Electron transfer reactions (M
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11.5 Reactions of ions in solutions
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11.5 Reactions of ions in solutions
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12.2 Fluorescence quenching (Stern-
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12.4 Radiationless processes in pho
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14 Combustion chemistry* 258 15. As
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16 Energy transfer processes* 260 1
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Appendix B 262 Appendix A: Useful p
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Appendix B 264 The Marquardt-Levenb
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Appendix C 266 • Convolution of t
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Appendix C 268 C.2 Application to t
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Appendix C 270 C.3 Application to p
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Appendix D 272 Final solutions for
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Appendix D 274 D.2 Special matrices
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Appendix D 276 I Multiplication by
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Appendix D 278 D.4 Coordinate trans
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Appendix D 280 D.5 Systems of linea
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Appendix D 282 D.6 Eigenvalue equat
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Appendix E 284 Secular equation: de
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Appendix E 286 Appendix E: Laplace
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Appendix F 288 Appendix F: The Gamm
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Appendix G 290 Appendix G: Ergebnis
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Appendix G 292 I Anschauliche Bedeu
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Appendix G 294 Ergebnis: = 1 X
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Appendix G 296 (2) Grenzfall für
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Appendix G 298 G.4 Mikrokanonische
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Appendix G 300 G.5 Statistische Int
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Appendix G 302 y = (G.7
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Appendix G 304 G.8 Zustandssumme f
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Appendix G 306 G.9 Zustandssumme f
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Physical Chemistry 3: — Chemical Kinetics — - Christian-Albrechts ...

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