物理化学厦门大学.ppt

Chapter 8 Chemical ics-2
Elementary plex reactions
Reaction ics and equilibrium state
Speculation of reaction mechanism
Activation energy for plex
reactions
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Elementary & Complex Reactions
Focuses
Elementary reactions
基元反应
Molecularity
分子数
Overall reactions
总包反应
Reaction order
反应级数
Reaction mechanism
反应机理
I. Concepts
II. ics of plex reactions
III. Steady-State Approximation
IV. Pre-equilibria
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I. Elementary Reactions & Overall Reactions
An elementary reaction refers to a single-step reaction involving a small number of molecules or ions.
For examples:
An overall reaction is a bined with a series of elementary reactions
For examples:
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Molecularity of Elementary Reaction
The molecularity of an elementary reaction is the number of ing together to react in an elementary reaction.
Elementary reaction
Unimolecular reaction单分子反应
Molecularity
Bimolecular reaction
双分子反应
Trimolecular reaction
三分子反应
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Law of Mass Action
rate law
Elementary reaction
For an elementary reaction, the rate is proportional to the concentration of of the reactant molecules that meet together.
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Reaction Mechanism
For an overall reaction, bination of a series of elementary-reaction steps is the reaction mechanism.
同一反应在不同的条件下,可有不同的反应机理。了解反应机理可以掌握反应的内在规律,从而更好的驾驭反应。一个反应机理需要经得起实验和理论的考验,有时需要作长期的大量的动力学研究。
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II. ics of plex reactions
Reversible (Opposing) reactions 对峙反应
Parallel reactions 平行反应
Consecutive reaction 连续反应
k1
A B
k-1
A
B
C
D
k1
k2
k3
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Reversible (Opposing) Reactions
mon situation is that the forward and the back reactions may not be elementary reactions, and may be first-, second- or third-order reactions
For examples
kf
A B
kb
kf
A + B C
kb
kf
A B + C
kb
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Reversible First-Order Reactions: Differential equation
t =0 [A]0 [B]0
t =t [A]0 – x [B]0 + x
t =te [A]0 – xe [B]0 + xe
k1
A B
k-1
[A]0+[B]0=[A]+[B]=[A]e+[B]e
k1/k -1 =[B]e/[A]e
[B