Choosing the Conditions

• The reaction between nitrogen and hydrogen is exothermic
• A high reaction temperature would give a fast rate of reaction but a low yield of ammonia
• A low reaction temperature would give a high yield of ammonia but a very slow rate of reaction
• In practice, a moderate temperature is used
• A high pressure encourages a high yield of ammonia
• The iron catalyst increases the rate of the reaction
• A moderate temperature, high pressure and iron catalyst are chosen to produce a reasonable yield of ammonia quickly - Even so, only some of the nitrogen and hydrogen react together to form ammonia