Estimation of rate constants as a function of temperature for the reactions W + XYZ = WX + YZ, where W, X, Y, and Z are H or O atoms
✍ Scribed by Robert Shaw
- Publisher
- John Wiley and Sons
- Year
- 1977
- Tongue
- English
- Weight
- 439 KB
- Volume
- 9
- Category
- Article
- ISSN
- 0538-8066
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✦ Synopsis
Rate constants have been estimated as a function of temperature for seven reactions of the type W + XYZ = WX + YZ, where W, X, Y, and Z are H and 0 atoms. From transition state theory and estimates of the heat capacities of activation, int kl[cm3/(mol. sec)] = 1015.87 e~p(AS,gfslR)TO.~~ exp[-(AH,,f, + 0.74)/RT] where int k is the rate constant per transferable atom for the forward and reverse reactions in the exothermic direction, and where AH& is in kcal/mol. Values of AS;& and AH;& were obtained from the above equation and previously measured and evaluated rate constants at 298°K. The results are summarized in a table. Rate constants were calculated at temperatures from 250 to 2000 K. The estimated rate constants were compared with recommended values. The results for AH& for reactions (15), ( 16), (17), and (19), in which a stable intermediate may precede the transition state, together with similar results previously found for reactions X + YZ = XY + Z, suggests that many such reactions may have values of AH;& that are close to zero. The result for the reaction 0 + 0 3 = 0 2 + 0 2 is, however, an exception to the foregoing perhaps because it is the reaction of a singlet with a triplet. AS;& for the same reaction is unexpectedly low.