7.21 Equilibrium constant, Kc for the reaction

N2 (g) + 3H2 (g) 2NH3 (g) at 500 K is 0.061

At a particular time, the analysis shows that the composition of the reaction mixture is 3.0 mol L–1 N2, 2.0 mol L–1 H2, and 0.5 mol L–1 NH3. Is the reaction at equilibrium? If not in which direction does the reaction tend to proceed to reach equilibrium?

The given reaction is:

                                   N2g           +     3H2g         2NH3g

At a particular time  3.0 mol L-1     2.0 mol L-1      0.5 mol L-1    

Now we know that,


Qc=NH32N2H23     =0.523.02.03     =0.0104

It is given that Kc=0.061.

Since QcKc, the reaction is not an equilibrium.

Since Qc<Kc, the reaction will proceed in the forward direction to reach equilibrium.