Practice of Kinetics (Comprehensive Chemical Kinetics, Volume 1)

4 ANALYSIS 101If Q is the molar heat of reaction,qg = W,Qand qw = W,Q.If the heterogeneous contribution is denoted by a,W, = (1-x)W and W, = xW.Substituting for qg and qw in terms of Q, LV and we have2rAT = __ 1 -a+a - In (R/r)]4 r+RHence from experimental observations of AT and W, a may be calculated. Markevit~h~~'found that, in the range 8-100 torr and 270-370" C using stoichiometricmixtures of hydrogen and chlorine for reaction (63)c1 = 0, indicating that the process is completely homogeneous. The effect of oxygenon ATJ W produced direct evidence that the chain reaction in this case is initiatedat the RV walls.4.5.6 Ultrasonic absorption measurementsThis technique has also been used for the well-known equilibrium (62). Soundabsorption results in a perturbation of the equilibrium, such that the dissociationconstant can be measured333. The magnitude of the absorption coefficient perwavelength at the frequency of maximum absorption can be related to the extentof dissociation of NzO,.4.5.7 Gas density balanceA gas density balance is shown in Fig. 71. A sealed bulb G at one end of a beamA is counterpoised by C. This is pivoted at F and enclosed in an envelope H.Gases of known (pa) and unknown (Pb) densities are run separately into H untilthe pointer is zeroed at D in each case. Then, for pressures pa and Pb required,Pb = Pa Pa/hReferences pp. 104-111