4.18 Consider the following CO oxidation reactions: VERVIE k CO + OH / CO+H of chemical me k 2 CO + O2 CO2 + 0, shemu where k (cm/gmol-s) = 1.17 107 T (K) 1.35 exp[+3000/RT (K)], k (cm/ ms, the gmol-s) = 2.50 1012 exp[-200,000/RT (K)], and R = 8.315 J/gmol-K. Calculate and compare the characteristic times associated with these two reactions for T = 2000 K and P = 1 atm. The CO mole fraction is 0.011 and the OH and O2 mole fractions are 3.68 10-3 and 6.43. 10-, respectively.