Question

19. Be sure to answer all parts. At 1000 K, a sample of pure NO2 gas decomposes: 2NO2(g) ⇌ 2NO(g) + O2(g) The equilibrium constant, KP, is 158. Analysis shows that the partial pressure of O2 is 0.35 atm at equilibrium. Calculate the pressure of NO and NO2 in the mixture. Pressure of NO: atm Pressure of NO2: atm

Answer 1

                        2NO2 (g) <--->          2NO (g)         +    O2 (g) ,

Initiall                       P                            0                               0

equilibrium              P-2X                      2X                                 X

given pO2 = X = 0.35 , hence pNO = 2 x 0.35 = 0.7 , pNO2 = P-0.7

Kp = ( pNO)^2 x ( pO2) / ( pNO2)^2

158 =(0.7^2 x 0.35) / ( P-0.7)^2

(P-0.7)^2 = 0.00108544

P-0.7 = sqrt ( 0.00108544) = 0.032946

P = 0.733

pNO = 0.7 atm

pNO2 = 0.733-0.7 = 0.033 atm