Given the values of K shown below, determine the value of K for the reaction

Question

Given the values of K shown below, determine the value of K for the reaction,

N₂(g) + 2 O₂(g) <=> 2 NO₂(g).

N₂(g) + O₂(g) <=> 2 NO(g)       K = 2

NO₂(g) <=> NO + 1/2 O₂(g)    K = 15

Give your answer to the 4 decimal places.

Correct Answer:

 0.0089 ± 1%

Answer 1

N₂(g) + 2O₂(g) <==> 2NO₂(g) ... target equation

Using Hess Law we can use the other 2 equations to obtain the target equation:

Eq.1: N₂ + O₂ <==> 2NO ... K = 2

Eq.2 reversed and x2: 2NO + O₂ <==> 2NO₂ ... K = (1/15)² = 0.0044

Add the 2 equations and cancel where appropriate....

N₂ + 2NO + 2O₂ ==> 2NO + 2NO₂ and multiply K values to get (2)(0.0044) = 0.0088 <--answer