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

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1. Introduction
1.1 Types of chemical reactions
• Homogeneous reactions:
— Reactions in the gas phase, e.g.,
H 2 +Cl 2 → 2HCl
— Reactions in the liquid phase, e.g., H + -transfer, reduction/oxidation reactions,
hydrolysis, . . . (most of organic and inorganic chemistry)
— Reactions in the solid phase (usually very slow, except for special systems
and special conditions; not covered in this lecture).
• Heterogeneous reactions:
— Reactions at the gas-solid interface, e.g.,
C()+12O 2
() → CO()
— Reactions at the gas-liquid interface, e.g., heterogeneous catalysis, atmospheric
reactions on aerosols (e.g., Cl release into the gas phase from
polar stratospheric clouds in antarctic spring)
ClONO 2 ()+HCl() → Cl 2 ()+HNO 3 ()
— Reactions at the liquid-solid boundary, e.g., solvation, heterogeneous catalysis,
electrochemical reactions (electrode kinetics), . . .
• Irreversible reactions, e.g.,
H 2 +12O 2 → H 2 O
• Reversible reactions, e.g.,
H 2 +I 2 À 2HI
• Composite reactions, e.g.,
CH 4 +2O 2 → CO 2 +2H 2 O
• Elementary reactions, e.g.,
OH + H 2 → H 2 O+H
CH 3 NC → CH 3 CN