In another stage in the production of nitric acid, ammonia is reacted with oxygen to form nitrogen oxide and water. Heat energy is given out when ammonia reacts with oxygen. The conditions chosen for the reaction are excess air, rather than just the right amount , a pressure of 10 atm, rather than atmospheric pressure and a temperature of 900 °C, rather than room temperature. Explain the effect of the conditions chosen on the equilibrium yield of nitrogen oxide and on the rate of attainment of equilibrium – 9034

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1. Adding excess air increases the concentration of oxygen, which shifts the equilibrium to the right-hand side, giving a higher yield of product. It also helps the reaction reach equilibrium faster.
   Increasing pressure affects the position of equilibrium. Since there are 9 gas molecules on the left and 10 on the right, higher pressure favours the left-hand side and gives a lower yield. However, the increased pressure also means particles are closer together, so collisions are more frequent and equilibrium is reached faster.
   Raising the temperature means particles have more energy and move faster, so there are more successful collisions. But because the forward reaction gives out heat, a higher temperature favours the reverse reaction (which takes in heat), so the equilibrium moves to the left and the yield is lower. Still, the reaction happens faster overall.

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