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

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10.2 <strong>Kinetics</strong> of heterogeneous reactions (surface reactions) 220<br />

I Fraction of occupied active surface sites Θ:<br />

• Adsorption rate:<br />

• Desorption rate:<br />

• Steady state:<br />

y<br />

y<br />

1 × (1 − Θ) × (10.38)<br />

−1 × Θ (10.39)<br />

1 (1 − Θ) = −1 Θ (10.40)<br />

1 =( −1 + 1 ) Θ (10.41)<br />

I Langmuir isotherm (Fig. 10.4):<br />

Θ =<br />

1 <br />

−1 + 1 =<br />

<br />

1+ <br />

(10.42)<br />

with<br />

= 1<br />

−1<br />

(10.43)<br />

I<br />

Figure 10.4: Langmuir adsorption isotherm.

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