Question

The pollutant NO is formed in diesel engines. The reaction fixes atmospheric nitrogen with oxygen to form NO. The reaction is: N₂(g) + O2(g) = 2NO(g). If the equilibrium constant for this reaction at elevated temperatures is 5.60E-11, then what is the partial pressure of NO gas if nitrogen is 1.50 atm and oxygen is 0.500 atm? The units are atmospheres.

Answer 1

N₂(g) + O2(g) -----------------> 2NO(g).

1.50      0.500                             2x

equilibrium constant Kp = 5.60 x 10^-11

Kp = [2x]^2 / [1.5][0.500]

5.60 x 10^-11 = 4x^2 / 0.75

x = 3.24 x 10^-6

partial pressure of NO = 2x = 2 x 3.24 x 10^-6

                                    = 6.48 x 10^-6 atm

partial pressure of NO = 6.48 x 10^-6 atm