However, nitrogen and hydrogen do not exist as single atom, they both exist as diatomic molecules held together by strong covalent bonds. Nitrogen molecules are held together by very strong triple covalent bonds and the single covalent bond between hydrogen atoms is also quite strong.
A lot of energy is needed to break these bonds and form atoms that can rearrange to form ammonia. Since the forward equilibrium reaction to form ammonia is exothermic, higher temperatures will favour the backward, endothermic reaction, which absorbs some of the added heat.
Hence the proportion of ammonia in the equilibrium mixture will be decreased by increasing the temperature.. Important conditions include: concentration of reactants and products presence of a catalyst temperature pressure only if gases are involved If a system is in equilibrium and a change is made that upsets the equilibrium, then the system alters in such a way as to counteract the change and a new equilibrium is established.
Rule 1: Temperature If the forward reaction is endothermic, increasing the temperature favours the formation of the product. These rules apply to all reactions. Rule 2: Pressure applies only to reactions with one or more gaseous reactants or products.
The use of the word optimum is misleading in this context. Python Javascript Linux Cheat sheet Contact. Chemistry - Why is the Haber process carried out at such high temperatures? Solution 1: As others have pointed out, it is purely kinetics, but you may still wonder, why. Solution 2: The answer mainly has to do with kinetic considerations, as aml points out. With a greater proportion of particles now able to react the reaction proceeds at a faster rate.
A catalyst is not used up during a reaction. Many inorganic catalysts are used to increase the rate of commercially important reactions. Two such reactions involve the production of ammonia by the Haber process and the production of sulfuric acid. In the Haber process, a n iron catalyst is used to increase the rate of the exothermic reaction given below.
During production of sulfuric acid by the Contact process a vanadium oxide is used as a catalyst. The reaction given below proceeds at a fast rate without the need for high pressure and high temperatures, both of which can increase, significantly, the cost of production.
The higher the pressure the better in terms of the rate of a gas reaction. Economic considerations: Very high pressures are very expensive to produce on two counts.
You have to build extremely strong pipes and containment vessels to withstand the very high pressure. That increases your capital costs when the plant is built.
High pressures cost a lot to produce and maintain. That means that the running costs of your plant are very high. The compromise : atmospheres is a compromise pressure chosen on economic grounds. If the pressure used is too high, the cost of generating it exceeds the price you can get for the extra ammonia produced. Catalyst Equilibrium considerations: The catalyst has no effect whatsoever on the position of the equilibrium.
Adding a catalyst doesn't produce any greater percentage of ammonia in the equilibrium mixture. Its only function is to speed up the reaction. Rate considerations: In the absence of a catalyst the reaction is so slow that virtually no reaction happens in any sensible time.
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