The reaction between nitrogen and hydrogen is exothermic. If nitrogen and hydrogen were reacted at 150 atm pressure and 300 °C, without a catalyst, some ammonia would be formed. In the Haber process a pressure of 150 atm and a temperature of 450 °C are used, in the presence of an iron catalyst.Explain why the conditions used in the Haber process are better than the first set of conditions for the manufacture of ammonia – 9033

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1. When temperature increases, molecules move faster and have more energy. This leads to more frequent and successful collisions, so equilibrium is reached faster.
   However, the yield becomes lower. This is because the forward reaction is exothermic, so increasing the temperature favours the reverse (endothermic) reaction. As a result, the equilibrium shifts to the left-hand side, meaning more ammonia breaks down into nitrogen and hydrogen.
   A catalyst can also be used. It helps the reaction reach equilibrium faster by lowering the activation energy and increasing the rate of both forward and reverse reactions, but it doesn’t affect the position of equilibrium or the yield.

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