How does high pressure affect the yield of ammonia?

High pressure affects the yield of ammonia in a crucial way by influencing the equilibrium of the reaction that produces ammonia from nitrogen and hydrogen gases. According to Le Chatelier's principle, when pressure is increased in a system involving gases, the equilibrium will shift in the direction that produces fewer gas molecules.

In the Haber process, which synthesizes ammonia, the balanced equation is:

N₂(g) + 3H₂(g) ⇌ 2NH₃(g)

This reaction showcases that there are four moles of gas on the left side (one mole of nitrogen and three moles of hydrogen) and only two moles of gas on the right side (two moles of ammonia). Therefore, when high pressure is applied, the equilibrium shifts to the right, favoring the formation of ammonia as it results in a decrease in the total number of gas molecules. This shift leads to an increase in the yield of ammonia when compared to lower pressure conditions.