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

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7.3 Thermodynamic interpretation of transition state theory 162<br />

so that, with ∆ ‡ = −1, weobtain<br />

Thus,viaEq.7.59:<br />

‡ ( )=<br />

( )= <br />

<br />

ABC ‡ ª<br />

A ª<br />

<br />

<br />

BC ª<br />

<br />

× 1<br />

µ 0<br />

= <br />

ª ‡ ( ) × . (7.77)<br />

ª<br />

0 <br />

ª ‡ ( )= µ<br />

0 <br />

exp ª<br />

− ∆ª‡<br />

<br />

<br />

, (7.78)<br />

in units of<br />

µ µ <br />

0 <br />

dim ( ( )) = dim × dim = l<br />

(7.79)<br />

<br />

ª mol s<br />

and with the standard state for the thermodynamics quantities explicitly indicated by<br />

the ª symbol.<br />

I<br />

Results:<br />

• Rate constant:<br />

( )= <br />

<br />

µ <br />

0 ∆<br />

ª‡<br />

exp exp<br />

ª <br />

µ− ∆ª‡<br />

<br />

<br />

(7.80)<br />

• Arrhenius activation energy:<br />

= 2 ln <br />

<br />

(7.81)<br />

If ∆ ª‡ 6= ( ) in the temperature range of interest:<br />

= ∆ ª‡ +2 (7.82)<br />

• Arrhenius preexponential factor:<br />

∆ ª‡ = − 2 (7.83)<br />

y<br />

( )= <br />

<br />

= 2 <br />

<br />

µ <br />

0 ∆<br />

ª‡<br />

exp ª <br />

µ<br />

0 ∆<br />

ª‡<br />

exp ª <br />

µ<br />

exp<br />

<br />

exp<br />

− <br />

− 2<br />

<br />

µ<br />

− <br />

<br />

<br />

(7.84)<br />

(7.85)<br />

Comparison with the Arrhenius expression = exp (− ) thus gives<br />

= 2 <br />

<br />

µ <br />

0 ∆<br />

ª‡<br />

exp ª <br />

(7.86)

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