Correct answer: K2K3^3 / K1
To derive the equilibrium constant for the given reaction, we manipulate the given reactions and their equilibrium constants. The reverse of the first reaction gives 2NH3 ⇌ N2 + 3H2 with equilibrium constant 1/K1. Adding this to the second and third reactions (appropriately scaled) gives the desired reaction, and the equilibrium constant becomes K2K3^3 / K1.