Practice of Kinetics (Comprehensive Chemical Kinetics, Volume 1)

350 TREATMENT OF EXPERIMENTAL DATAThe results areThus, for a reaction with constant stoichiometryA = 2Pproceeding under constant volume conditions with a rate of disappearance of Agiven bythe rate at which product appears isSince most reactions are studied under conditions where the volume remainsconstant or almost so, we shall confine the remainder of the discussion of thischapter to these cases.In order to rigorously test the data for consistency with the rate expression---d[A1dt- k[AIa[Blbwith a particular pair of a and b values, we require the corresponding integratedexpression. The problem is that in a particular case we have no prior knowledgeof the orders a and b and so we are unable to select the appropriate integratedequation. Since the value of (u+b) seldom exceeds 2 and since a and b cannctusually take on values other than 0, 0.5, 1.0, 1.5, or 2.0, there are a limitednumber of possible integrated forms of eqn. (1 1) for a given vB/vA. In principle,therefore, we could proceed by inserting the concentration-time data into eachof the possible integrated equations until we obtained a constant rate coefficient.We shall discuss this method more critically later on but for the moment it isobvious that, if some way can be found of discovering the limits between which a