Activation energy, apparent defining equation

Care should be taken in defining the procedure for calculating values of k fi om the experimental data. There is always the possibihty that the apparent is a compound term containing several individual rate coefficients for separable processes (such as nucleation and growth). It is important that the dimensions of k (and hence of A) should be (time). For example, the power law (Table 3.3.) should be written as = kt and not as ar = k t. Similarly the Avrami-Erofeev equation (An) is [-ln(l - a)Y = kt. The use of k in place of A in the Arrhenius equation will produce an apparent activation energy /i, which is n times the conventional activation energy obtained using k. 

In the case of electron transfer mediators immobilized on electrode surfaces, one can define a specific activity, S, as the quotient between catalytic peak current, /peat, and catalyst deposition charge, Cc.u (Sa = ipcn/Qcut) (Wang et al., 2004). In most systems, one can define apparent activation energy, satisfying an Arrhenius-type equation ... 

An apparent activation energy (Eapp) can be defined by the following equation ... 

Relative activation enthalpies (Aif) in Table 2 were converted to o% kx k ) at 298 K, and were plotted against Hammett a constants. Here, we used enthalpies, because the size of the entropy and hence the free energy depend much on low frequencies, which are less reliable than higher frequencies, especially for compounds with weak interactions such as TS (8). The use of free energy (AG ) gave similar correlations with more scattered points. As for the Hammett o constant, we used dual-parameter o constants in the form of the Yukawa-Tsuno equation (LArSR equation) (9) as defined in eq 3. Here, the apparent a constant (aapp) has a variable resonance contribution parameter (r), which varies depending on the nature of the reaction examined for t-cumyl... 

The apparent energy of activation of a chemical reaction, or Arrhenius energy of activation, is defined by the equation... 

The apparent energy of activation as defined by Eq. 1 is obtained by differentiation of the Arrhenius equation (9)... 

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