A Deeper Insight into the Meaning of k and

1 A Deeper Insight into the Meaning of k° and a. At this point a better understanding of the two factors k° and a is called for. 

The heterogeneous standard (or conditional) rate constant k° measures the intrinsic ability of a species (say, Ox) to exchange electrons with the electrode in order to convert to its redox partner (say, Red). A species with a large k° will convert to its redox partner on a short time scale a species with a small k° will convert to its redox partner on a long time scale. 

The largest values for the standard rate constant k° (expressed in metre/second) range from 0.01 m s-1 to 0.1 m s-1, and commonly characterize redox processes which do not involve significant molecular reorganizations. 

The smallest values for the standard rate constant k° are around 10 11 m s-1. 

We must however note that even if one partner of a redox couple does not possess a high propensity to exchange electrons with the electrode (i.e. low k°), we can force it to increase its electron transfer rate by applying to the working electrode a potential value higher than the formal electrode potential Eo of the couple itself (i.e. more negative for a reduction process more positive for an oxidation process). In fact, as seen  

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