Consider the following chain-reaction mechanism for the high-temperatureformation of nitric oxide, i.e., the Zeldovich mechanism
:
O + N2------ NO + N Reaction 1
N + O2------ NO + O Reaction 2
A. Write out expressions for d[NO] / dt and d[N] / dt.
B. Assuming N atoms exist in steady state and that the concentrations of O, O2, and N2 are at their equilibrium values for a specified temperature and composition, simplify your expression obtainedabove for d[NO] / dt for the case of negligible reverse reactions.(Answer: d[NO]/d 2 [O] [N ] . 1 2 t k f eq eq = )
C. Write out the expression for the steady-state N-atom concentrationused in part B.
D. For the conditions given below and using the assumptions of part B,how long does it take to form 50 ppm (mole fraction â 106) of NO?
T = 2100 K,
rho = 0.167 kg/m
MW = 28.778 kg/ kmol,
Xo,eq = 7.6.10 (mole fraction),
Xo2,eq = 3.025.10^-3 (mole fraction),
Xn2,eq = 0.726 (mole fraction),
k1f = 1.82.10^14 exp[-38,370/T(K)] with units of cm/gmo
Calculate the value of the reverse reaction rate coeffi cient for the fi rstreaction, i.e., O +â + N NO 2 N, for a temperature of 2100 K.F. For your computations in part D, how good is the assumption thatreverse reactions are negligible? Be quantitative.G. For the conditions of part D, determine numerical values for [N] and ÏN.(Note: k2 f = 1.8 â 1010 T exp(â4680 / T) with units of cm3/ gmol-s.)
