Precision of Rate Measurements for Simple Systems

It is of some interest to investigate the nature of the errors in kinetic data so that we may obtain some idea of data reliability. There are two related quantities which we can calculate directly from an isothermal experiment the specific rate constant or a partial reaction time (e.g., the half-life). These are not independent, and one may be calculated from the other. The quantity that completes the empirical description of a reaction system is the activation energy. We have seen that this may be calculated from a knowledge of the specific rate constants at different temperatures. 

The errors inherent in any physical measurement are of two kinds. The first category, which is relatively simple to deal with, involves errors that are random. The second category, which is more difficult to detect and so also difficult to handle, includes systematic errors, i.e., errors which are not random but inherent in the reaction studied or the methods employed. A typical example of the latter would be the small contribution of a secondary reaction, the extent of which is determined by the concentrations and temperatures. It is thus inherent in the nature of the system observed, and the magnitude of the errors involved in neglecting this secondary reaction is not random but directly related to the state of the system. Errors due to small amounts of secondary reactions are the most frequent type of systematic error encountered in kinetic studies.  

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