The reaction is: (4NH_3(g) + 3O_2(g) \rightleftharpoons 2N_2(g) + 6H_2O(g))

We need to write the expression for the equilibrium constant ((K)).

The expression for the equilibrium constant (K) for the reaction is:

K = [N2]^2[H2O]^6 / [NH3]^4[O2]^3