Practice of Kinetics (Comprehensive Chemical Kinetics, Volume 1)

368 TREATMENT OF EXPERIMENTAL DATATABLE 2Run 1 ... Runi .. . Run rtl0 a, tro cro fro cr,coefficient is that value which minimizes the weighted sum of the squares of thedeviations of the experimental points from the equationf(a) = Z-mk(t-to)the weights being calculated from the experimental errors in each value of a.In this equation, f(a) is the function suggested by the preliminary examination ofthe data, 1 is a constant, k is the rate coefficient and m is another constant whosevalue can be found from Table 1. In the computation work which follows, theequations of Table 1 must be rearranged so as to correspond to the form of theabove equation to avoid confusion over signs.For example, eqn. (36)In l/a = k(t-to)is clearly of the formIn a = constant - k( t - to)and so f(a) in this particular case is In (a). On the other hand, eqn. (38)(l/a) - 1 = k[A],(t- to)must be written- l/a = constant - k[AIQ(t- to)-so that f(a) in this case is - l/a.The important point to notice is that the graph of f(a) against (t-to) is notconstrained to pass through the value of f(a,) at t-to c 0. The reason for this isthat there are usually systematic errors in the reaction time resulting from the