Practice of Kinetics (Comprehensive Chemical Kinetics, Volume 1)

344 TREATMENT OF EXPERIMENTAL DATAfundamental point of view, it is the interaction of the reactants which determinesany particular reaction rate. We shall follow this practice throughout this chapterand hence we shall refer extensively to the reaction rate as the rate of disappearanceof a particular reactant, uiz.-d[reactant]dtIn most of the discussion, we shall consider that our reaction involves only tworeactants A and B giving products P and Q, in which case we shall identify thereaction rate with the rate of disappearance of the reactant A, viz.-431dtNow, it is known from the results of many kinetic investigations that a largenumber of factors may influence the rate of a reaction. Some of these factors are:(1) the concentrations of the reactants;(2) the concentrations of the products;(3) the concentrations of any catalysts added (i.e. the concentrations of any substanceswhich do not appear in the reaction stoichiometry and which are thereforerecoverable unchanged in amount at the end of the reaction);(4) the temperature;(5) the total pressure on the system;(6) the viscosity of the reaction mixture;(7) the dielectric constant of the reaction mixture;(8) the total ionic strength of the reaction system;(9) the intensity of radiation absorbed by the reaction system.It is the basic objective of every experimental kinetic investigation to discoverthe quantitative relationship between the instantaneous reaction rate and thecorresponding values of those factors on which it depends. In simple cases, theinstantaneous rate of disappearance of reactant A can be expressed as the productof two functions, one dependent on the concentrations of the reactants only andthe second dependent on the other reaction parameters such as temperature,[catalyst], pressure, etc. i.e.-- -dCA1 - k(T, [catalyst], P etc.) x f([reactants])dtIn these simple cases, the explicit form of the second function for a reaction involvingtwo reactants A and B.is