Transport and reaction in the light of chemical kinetics

in order to map out the region of validity of the linear laws we turn to the simple kinetic laws of chemical kinetics [336] for transition rates (Table 6.3). These are not limited to the near-equihbrimn conditions (Fig. 6.1), but apply from the start to dilute systems. For simphcity s sake let us consider, only one position coordinate, refer to oiu general reaction (Eq. (6.1)) (only two species and two sites) and formulate  

The generalized flux (composed of forward and backward contributions, i.e. J — J) refers to the net particle number passing from x to x in unit time during that process the particles may or may not change their nature. In the case of a homogeneous 

The tilde indicates that the actual chemical barrier (AG ) is modulated by the 

More precisely the transition state corresponds to a saddle-point. This is shown in Fig. 6.3 the fastest route is that path from the set of all parallel processes which exhibits the most favourable transition state. On the other hand, the same transition state forms the most difficult serial part of that specific path (bottleneck) . Again, we first consider he chemical reaction. The barrier is now a purely diemical threshold (AG — AG, k — k, J 7 ). Note that Eq. (6.17) can be appropriately 

19) we used the proportionality sign, simply because (in contrast to the fluxes) the reaction rate is volume related. Since = 0 in equilibrium, it follows that Kr = k/ic. Because of ArG = -1-RTlnQR/KR (cf. Section 4.2) we obtain 

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