As we saw in 22.37, reaction with the hydroxyl radical OH is the main path by which CH4

Chapter 22, Problem 22.38

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As we saw in 22.37, reaction with the hydroxyl radical OH is the main path by which CH4, a by-product of many natural and industrial processes, is removed from the lower atmosphere. T. Gierczak, R.K. Talukdar, S.C. Herndon, G.L. Vaghjiani, and A.R. Ravishankara (J. Phys. Chem. A 101, 3125 (1997)) measured the rate constants for the bimolecular gas-phase reaction CH4(g) + OH(g)CH3(g) + H2O(g) and found A = 1.13 109 dm3 mol1 s1 and Ea = 14.1 kJ mol1 for the Arrhenius parameters. (a) Estimate the rate of consumption of CH4. Take the average OH concentration to be 1.5 1021 mol dm3, that of CH4 to be 4.0 108 mol dm3, and the temperature to be 10C. (b) Estimate the global annual mass of CH4 consumed by this reaction (which is slightly less than the amount introduced to the atmosphere) given an effective volume for the Earths lower atmosphere of 4 1021 dm3.