The emission of an air pollutant is often influenced more by reaction kinetics than by chemical equilibrium. Verify whether this is true for a hypothetical case of hydrocarbon (methane) combustion. The pseudo-first-order rates of the relevant parallel reactions can be represented as follows:
CH4 + 1.5O2 = CO + 2H2O k1 (s-1) = 0.5x108 exp(-20000/T)
CH4 + 2O2 = CO2 + 2H2O k2 (s-1) = 1.0x106 exp(-15000/T)
Compare the equilibrium composition with the composition achieved after burning 50 mol/L of CH4 for 1 s at 950 K and 1 atm air. And for 20 s?
Hints: (a) Solve three equations in three unknowns, [CH4], [CO], [CO2], to determine the kinetics-governed composition. (b) Remember that conductances (rate constants) are additive for simultaneous processes (reactions).