note HO2 | Lee 1982 report the rates for the competing reactions {Cl } + {HO2 } -> {HCl } + {O2 } (1a) and {Cl } + {HO2 } -> {OH } + {ClO } (1b) at low p and at T 250 - 420 K. The total rate was found independent of T, k1 = (4.23 +- 0.70) E-11 cm3/molecule/s. k1a = (1.8 +- 0.5) E-11 exp[(170 +- 80)/T] cm3/molecule/s and k1b = (4.1 +- 0.8) E-11 exp[(-450 +- 60)/T] cm3/molecule/s from T-dependent ratio k1b/k1 = (1.09 +- 0.06) exp[(-478 +- 17)/T]. The errors are claimed to be 95% confidence limits. Lee 1982 combine their k1b = 9.1 E-12 at 298 K with the reverse rate at 298 K of Leu 1979 of 9.1 E-12 cm3/molecule/s to obtain K1b = 1 from which they obtain DHf298(HO2) = 3.3 +- 0.6 kcal/mol. The rates lead to K298 = 0.0 +- 0.6 and DG298 = 0.0 +- 1.4 kJ/mol (assuming a 50% uncertainty in the reverse rate of Leu 1979). Later, Hills 1984 have remeasured the reverse rate and found k = (8.0 +- 1.4) E-12 exp[(235 +- 46)/T] cm3/molecule/s with a branching ratio of 0.86 +- 0.14, from which they obtain DHf298(HO2) = 3.0 +- 0.4 kcal/mol. The new rate leads to K298 = 0.6 +- 0.2 or DG298 = 1.3 +- 1.0 kJ/mol. |