Question

How do I do this???

Answer 1

The chemical reaction is as follows:

2NH3(g) = N2(g) + 3H2(g)

We do the ice method to answer this. 
                
            NH3            N2             H2
I          1.22              0                0
C          -2x              x                3x 
E        1.22 - 2x       x                3x

Kc = [h2]^3 [n2] / [nh3]^2
4.0 × 10^–2 = 27x^3(x) /  (1.22 - 2x )^2
x = 0.259 mol

H2 = 0.259/1 = 0.259 mol/L