The Haber process is a method of Ammonia production developed by Fritz Haber. This is the most common way of producing ammonia, and usually occurs at an industrial level. The Haber process mixes nitrogen and oxygen to produce ammonia through an exothermic reaction:
N2 (g) + 3H2(g) ↔ 2NH3 (g) Δ=-92kJ
(N2 (g) + 3H2(g) ↔ 2NH3 (g) +Heat)
Pressure is kept at 200kPa. There is 4 moles of substance on the left (one mole of nitrogen and three moles of hydrogen) and 2 moles on the right (two moles of ammonia).The equilibrium to shift to the right (to the side with fewer moles) as the pressure is increased, in doing so, more ammonia is produced.
Temperature is maintained at 400-450oC. The equation suggests that heat should be minimized to maximize ammonia production, however this slows down the reaction and produces very little ammonia. High temperatures speed the reaction up so that even though the equilibrium shifts left, the amount of ammonia produced is still higher than when temperatures are reduced and the reaction slows down. At this temperature, Ammonia production is maximized at a 15% yield.
The table shows the relationship between the equilibriumconstant and the temperature.A large equilibrium concentration indicates large amounts of products, and in this case, ammonia. Even though the equilibrium constant is largest at 300K, the reaction would occur too slowly for any significant concentrations of ammonia to be produced in a short period of time, making it costly. However, at 400K, the reaction occurs fast enough to maximize the yield of ammonia.
Increasing the Concentration of N2 and H2. To increase the concentrations of NH3, one method is to increase the concentration on the left (i.e. Increase nitrogen and hydrogen concentrations), so that the equilibrium shifts to the right, and more NH3 is produced to adjust this disturbance.
An Iron Catalyst is used to speed the reaction up, it has no effect on the concentrations, only the speed of the reaction increases so that ammonia can be produced more quickly. This reduces the cost of production as it minimizes the time needed to produce ammonia. The iron catalyst also eliminates the need for excessively high temperatures.
Ammonia is the world’s sixth most produced chemical, with 80 Billion kilograms produced annually. Ammonia is primarily used in artificial fertilizers, cleaning products such as detergents and shampoos, and in explosive production. It is a key ingredient in the agricultural sector (83% of ammonia produced is used in the agricultural sector) as it is used in artificial fertilizers that significantly increases crop yield, which is essential to meet the demands of the growing population. There are however negative impacts, such as increased soil acidity, which can be harmful to bacteria and small insects that live on the land covered in fertilizers. In addition, the fertilizer can leach into drains and water bodies, which can increase the toxicity of the water and lead to rapid algae growth on these bodies of water, which can kill organisms within the pond as light is blocked. The chemicals in the cleaning products can also leach into water sources, causing them to become more toxic and hazardous. Water that contains shampoo can increase the toxicity of the water which it drains into.
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