Question

1. (14 pts) Consider the following unbalanced gas-phase exothermic reaction, N2 + O2 = NO2 This is a reaction involved in the production of smog. The heat of formation of NO2 from the elements is A He = 33.18 kJ/mol. This is an endothermic process. The 4, Gof NO2 is 51.31 kJ/mol. a) Balance the reaction. b) Calculate the equilibrium constant at room temperature (300 K). c) If we assume that in our atmosphere the partial pressure of oxygen is 0.2 bar and the partial pressure of nitrogen is 0.8 bar, what is the partial pressure of NO2 under these conditions? d) Inside an engine, the temperature can reach as high as 1500°C (1773 K). What is the equilibrium constant for production of NO2 under these conditions? e) During combustion, the partial pressures of nitrogen and oxygen can reach 20 bar and 2 bar, respectively, and 1500°C. What is the partial pressure of NO2 under these conditions? Is this above the acceptable level of around 1 x 10-5 bar?

Answer 1

a) Balanced equation for the reaction N2(g) +202(g) + 2NO2(g) b) Equilibrium constant AG° =-RT In K, In K, - AG° (51.31kJ) (8.314x10- kJ /mol K)(300K) =-20.57 Ky =e-20.57 = 1.17x10-9 c)K - (P.No.)" [P.][P] (P.xo.)= VK,(Px)(pc.) = V1.17x10-9 (0.8)(0.2) =6.1x10 bar