7.21     Equilibrium constant, Kc for the reaction

                N_{2}_{(g)}+3H_{2}_{(g)}\rightleftharpoons 2NH_{3}_{(g)}

At 500 K is 0.061 At a particular time, the analysis shows that 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?

Answers (1)
M manish

The given reaction is:

                                            N_{2}_{(g)}+3H_{2}_{(g)}\rightleftharpoons 2NH_{3}_{(g)}           

at a particular time:           3.0molL-1  2.0 molL-1     0.5molL-1

Now, we know that,

Qc = [NH_3]2^ / [N_2][H_2]^3
          \\ = (0.5)^2 / (3.0)(2.0)^3\\ = 0.0104

It is given that Kc = 0.061

Since, Qc \neq  Kc, the reaction mixture is not at equilibrium.

Again, Q_c < K_c, the reaction will proceed in the forward direction to attain the equilibrium.