Question

Help with a combustion problem!

A flame exhaust has the composition (by volume) of 14% CO2, 2% O2, 12% H20, the rest N2 and a flame temperature of 1900 K at a pressure of 31 atm. Calculate the equilibrium mole fraction of H from the dissociation reaction: H2O H2H + 1202 Assume that the effect on the mole fractions of the major species is negligible.

Answer 1

Given datai percentage of coge 14% Percentage of O2 = 2% Percentage of 420 = 12% Percentage of M2 = 100-(14+2 +12) = 70% Flame temperature = 1900k Pressure (P) = 31 atm Solution, Effect of the mole fractions of the major species is negerilible (ginen). H₂O + 2H+ / 02 when the temperature of a system changes the Henry constant also changes. The temperatuse dependence of equiliboren constant can be described with the van't Hoff equation HC) = H expert en T.= reference tenperature = 298.18K Ho= Henry constant at To The rand equation in this form is only valid for a limided temperature range in which 4501H does not change much with temperature values of (AsiH) gares O2 H₂ for some are constant 1602 N2 2400 1300 1700

7.8x10-50 x 1H₂ H2 Too 831 = 4.34 atm 108x31 = 3.72 atm Calculate Henry constant for O2 at 190k (K) = 4.3x107 exprox (1500 298.15 = 526 21 x 10tt atm Calculate Hency constant of Hz. 4 = 11.02 X 10 atm Partial pressure of O2 = (P) = 21 22 x 31= 0.62 atm partial pressure of co2 = (p) coz? 14 partial pressure of Ho = (P220 = partial pressure of N₂ = (PN2 = 21.7 atm Now H₂ + 1 202 H₂O - Menry constant for (+60) = (KH) HO (ku) 11:02x107+ £x 526:21x107 274.02xyot atm. 12 70 Tos (Ro).+ 4 (Rt)oz

reations H2O 2H + 1/ 02 partial pressure of H₂O = ax partial pressure of H 4 portial pressure of Og => 342 = 2x(Þ)+ 1 x 0.62 3 (P)4 = 1.705 atm According to Henry's low! (P) + = (KH) 4 X (2), is the mole fraction of H where Henry constant for equation! Ho 2h+ 1 O2 (FH) 120 274.02 X10 = = 2 (KH)+ (K) 0*= 2 (KH)*+ ** 526-21x104 5.4575 x 10 atm From equation 6 1.705 5.4575*107 BebH 0.3124 x 10 Any

pe pa Henry's law constants (gases in water at 298.15 K) p Caq р Caq нер H HCC Cag р Cgas mol (atm) (dimensionless) mol L. atm 12 Gas L.atm 02 770 4.3 x 104 3.2 x 10-2 1.3 * 10-3 7.8 x 10-4 1300 7.1 x 104 1.9 x 10-2 H2 CO2 N2 29 3.4 x 10-2 1.6 % 103 8.3 * 10-1 1600 6.1 x 10-4 9.1 x 104 1.5 x 10-2 He 2700 3.7 x 10-4 15 x 105 9.1 x 10-3 Ne 2200 4.5 x 10-4 1.2 x 105 1.1 x 10-2 Ar 710 1.4 x 10-3 40 x 104 3.4 x 10-2 CO 1100 9.5 x 10-4 5.8 x 104 2.3 * 10-2