In the reaction

N₂(g) + 3H₂(g) ⇔ 2NH₃(g), Δ_fH^o = -46.1 KJ mol^-1

the yield of ammonia is expected to be maximum at

High Temperature and High Pressure

On a large scale, ammonia is manufactured by Haber’s process. 

N₂(g) + 3H₂(g) ⇔ 2NH₃(g), Δ_fH^o = -46.1 kJ mol^-1 ;

the yield of ammonia is expected to be maximum at high temperature and high pressure.

In accordance with Le Chatelier’s principle, high pressure would favour the formation of ammonia. The optimum conditions for the production of ammonia are a pressure of 200 × 10⁵ Pa (about 200 atm), a temperature of ~ 700 K and the use of a catalyst such as iron oxide with small amounts of K₂O and Al₂O₃ to increase the rate of attainment of equilibrium.