Problem 13.78 The air pollutant NO is produced in automobile engines from the hi

Question

Problem 13.78

The air pollutant NO is produced in automobile engines from the high-temperature reaction N2(g)+O2(g)2NO(g);Kc=1.7×103at 2300 K.

Part A

If the initial concentrations of N2 and O2 at 2300 K are both 1.38 M, what are the concentrations of NO when the reaction mixture reaches equilibrium?

Part B

If the initial concentrations of N2 and O2 at 2300 K are both 1.38 M, what are the concentrations of N2 when the reaction mixture reaches equilibrium?

Part C

If the initial concentrations of N2 and O2 at 2300 K are both 1.38 M, what are the concentrations of O2 when the reaction mixture reaches equilibrium?

Explanation / Answer

N2(g)+O2(g)2NO(g)

Kc=1.7×103

PART A

[N2] = 1.38

[O2] = 1.38

[NO] = 0

find NO in equilibrium

[N2] = 1.38 - x

[O2] = 1.38 - x

[NO] = 0 +2x

Substitute all

K = [NO]^2 / [N2][O2]

1.7×103 = (2x)^2 / (1.38 - x)^2

solve for x

1.7×103 = (2x) / (1.38 - x)

(1.38 - x)(1.7*10^-3) = 2x

1.38-x = (2/(1.7*10^-3))x

1.38-x = 1176.5x

138 = 1177.5x

x = 138/1177.5

x = 0.1172

Substitute in all concnetrations in equilibrium

[N2] = 1.38 - 0.1172 = 1.2628

[O2] = 1.38 - 0.1172 = 1.2628

[NO] = 0 +2x = 2*0.1172 = 0.2344

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