The equilibrium constants of the following are: N2 + 3H2 ⇌ 2NH3; K1 N2 + O2 ⇌ 2NO; K2 H2 + 1/2O2 → H2O; K3 The equilibrium constant (K) of the reaction: 2NH3 + 5/2O2 ⇌ 2NO + 3H2O, will be:

N2 + 3H2 ⇌ 2NH3; K1. (1)
N2 + O2 ⇌ 2NO; K2. (2)
H2 + 1/2O2 → H2O; K3. (3)
We have to find the equilibrium constant for the reaction:
2NH3 + 5/2O2 ⇌ 2NO + 3H2O
From (1), we have:
2NH3 ⇌ N2 + 3H2; 1/K1
Multiplying (2) by 2, we get:
2N2 + 2O2 ⇌ 4NO; K2^2
Multiplying (3) by 3, we get:
3H2 + 3/2O2 → 3H2O; K3^3
Adding the above three equations, we get:
2NH3 + 5/2O2 ⇌ 2NO + 3H2O
Hence, the equilibrium constant for this reaction is:
K = K2^2 * K3^3 / K1