Question

Understanding reactions involving normal components of air is essential for solving problems 16. dealing with atmos pheric pollution. Here is a reaction sequence involving N2 and O2, the most abundant gases in air. Nitrogen dioxide is a toxic pollutant that contributes to photochemical smog. Using the reactions given below, determine the equilibrium constant for the following reaction: N2(0)202g) 2NO2 (9) Ke ? N2(g) O2(g) 2NO () Ke= 4.3 x 10-25 NO2(g) NO (g) O2(g) Ke=1.25x 10 5

Answer 1

Q16.

Reaction 1 : N₂ (g) + O₂ (g) $\rightleftharpoons$ 2 NO (g) : K_c1 = 4.3 x 10^-25

Reaction 2 : NO₂ (g) $\rightleftharpoons$ NO (g) + 1/2 O₂ (g) : K_c2 = 1.25 x 10^-5

If we multiply Reaction (2) by a factor of 2, we get

Reaction 3 : 2 NO₂ (g) $\rightleftharpoons$ 2 NO (g) + O₂ (g)

K_c3 = (K_c2)²

K_c3 = (1.25 x 10^-5)²

K_c3 = 1.5625 x 10^-10

If we reverse Reaction (3), we get

Reaction 4 : 2 NO (g) + O₂ (g) $\rightleftharpoons$ 2 NO₂ (g)

K_c4 = 1/K_c3

K_c4 = 1/(1.5625 x 10^-10)

K_c4 = 6.4 x 10⁹

Now add Reaction (1) and Reaction (4), we get

N₂ (g) + 2 O₂ (g) $\rightleftharpoons$ 2 NO₂ (g)

This is the desired reaction.

K_c = (K_c1) * (K_c4)

K_c = (4.3 x 10^-25) * (6.4 x 10⁹)

K_c = 2.752 x 10^-15