Question

In the car exhaust manifold, (>215 degrees C) N2 and O2 combine to form NO, which moves on with additional O2 to form NO2(smog).

Step 1: N2 + O2 <-- --> 2NO K1 = 4.3 x 10^-25

Step 2: 2NO + O2 <-- --> 2NO2 K2= 6.4 x 10^9

Write the balanced net equation, determine Kc for the reaction (first prove that overall K is the same as the product of K for each individual step), and based on the magnitude of K is the reaction product or reactant favored?

Answer 1

Step 1: N2 + O2 <-- --> 2NO K1 = 4.3 x 10^-25

   K1   = [NO]²/[N2][O2]

4.3*10^-25 = [NO]²/[N2][O2]

Step 2: 2NO + O2 <-- --> 2NO2 K2= 6.4 x 10^9

        K2   = [NO2]²/[NO]²[O2]

      6.4*10⁹ = [NO2]²/[NO]²[O2]

overall reaction N2 + 2O2 -----> 2NO2

   Kc = [NO2]²/[N2][O2]²

Kc   = K1*k2

      = 4.3*10^-25 *6.4*10⁹ = 27.52*10^-16 = 2.7*10^-15

balanced net equation

N2 + O2 ----> 2NO2