How do I write the equilibrium expression (K) for each of the following gas phase reactions?

Question

A.N2 (g)+O2==>2NO (g)

B. 2NH (g)==>N2 (g)+ 3H2 (g)

C. NH3 (g)==> 1/2N2(g)+3/2H2(g)

D. 2N2 (g)+6H2 (g)==>4H3 (g)

 

 

Answer 1

The equilibrium constant, K, is the products/reactants, each raised to a power equal to the coefficient.  For example, in

aA + bB <==> cC + dD, the K = [C]^c[D]^d/[A]^a[B]^b

When gases are present, they can be presented as concentration or partial pressure.  For this problem, you would have

(A).  K = [NO]²/[N₂][O₂]  where [NO], [N₂] and [O₂] can be concentration (M) or partial pressure

 

The others are done the same way.