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Chemical equlibria and the Haber process
Transcript of Chemical equlibria and the Haber process
When a reversible reaction occurs in a closed system, an equlibrium is reached when the reactions occur at exactly the same rate in each direction. Altering Conditions The relative amounts of all the reacting substances at equlibrium depend on the conditions of the reaction.
The reaction conditions you need to know about are:
Pressure The Haber Process Economics of the
Haber Process What are the optimum conditions in this industrial process?
How do they effect
Rate? At a dynamic equlibrium reactions are still happening! It just looks like its stopped! Henri Le Chatelier Any change imposed on a system at a dynamic equlibrium will cause it to shift in the direction that opposes the change. What this means is that reactions at equlibrium want to stay there.
if you heat it up, the reaction will increase the direction that will cool down the reaction.
if you lower the pressure the reaction will increase the direction that increases the pressure. If the temperature is raised, the yield from the endothermic direction increases and the yield from the exothermic direction decreases. If the temperature is lowered, the yield from the exothermic direction increases and the yield from the endothermic direction decreases. In gaseous reactions, an increase in pressure will favour the direction that produces the least number of molecules as shown in the balanced equation. 2 Moles 1 Mole Higher
pressure Making Ammonia Exothermic Endothermic So...
if you raise the temperature you will encourage the endothermic direction (to cool the reaction down).
if you lower the temperature you will encourage the exothermic direction (to warm the reaction up). 4 Moles 2 Moles High
if you raise the pressure you will encourage the low pressure direction (to reduce the pressure).
if you lower the pressure you will encourage the high pressure direction (to increase the pressure). BUT! You must not forget about the effect on the rate of reaction!
low temperature slows down reactions
high temperature speeds up reactions
low pressure slows down reactions
high pressure speeds up reactions Remember...
heating a process is expensive
high pressures are dangerous and expensive to maintain
if the rate of a reaction is very slow it may not produce enough product to make it economic Fritz