Lexi_bohin
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Describe and explain how changing the pressure and temperature would affect the position of equilibrium in the reaction of nitrogen and hydrogen. the equation is N2+ 3h2↔ 2NH3 (numbers after are meant to be little
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joebloggs1239
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(Original post by Lexi_bohin)
Describe and explain how changing the pressure and temperature would affect the position of equilibrium in the reaction of nitrogen and hydrogen. the equation is N2+ 3h2↔ 2NH3 (numbers after are meant to be little
As this is a GCSE question I am assuming you do not need to explain it in terms of Kc (the equilibrium constant).

If you look at the equation N2 + 3H2 ↔ 2NH3 (I've written it out again to make it easier to understand) you will notice that 2 moles of products (NH3) are formed for every 4 moles of reactants (N2 and H2) which are added. As a result, when the pressure of the system increases, using Le Chatalier's principle, the equilibrium will shift to favour the reaction that produces the fewest moles of gaseous molecules - in this case it is the forward reaction.

This reaction is exothermic (and this should be stated in the question) and therefore increasing the temperature would result in the backwards reaction being favoured - the reaction of NH3 to form its constituent molecues (N2 and H2) as this will reduce the temperature of the system overall. If the reaction was cooled then the forward reaction would be favoured (it may be worth noting here also that by cooling the reaction you will decrease the rate of the reaction as well and therefore in industries that use the Haber process for the production of ammonia, the temperature is not too low).

I hope this has helped - if you need to make reference to Kc then you should be stating that the value of Kc changes with temperature but remains constant when any other condition of the reaction is changed.
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Lexi_bohin
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#3
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(Original post by joebloggs1239)
As this is a GCSE question I am assuming you do not need to explain it in terms of Kc (the equilibrium constant).

If you look at the equation N2 + 3H2 ↔ 2NH3 (I've written it out again to make it easier to understand) you will notice that 2 moles of products (NH3) are formed for every 4 moles of reactants (N2 and H2) which are added. As a result, when the pressure of the system increases, using Le Chatalier's principle, the equilibrium will shift to favour the reaction that produces the fewest moles of gaseous molecules - in this case it is the forward reaction.

This reaction is exothermic (and this should be stated in the question) and therefore increasing the temperature would result in the backwards reaction being favoured - the reaction of NH3 to form its constituent molecues (N2 and H2) as this will reduce the temperature of the system overall. If the reaction was cooled then the forward reaction would be favoured (it may be worth noting here also that by cooling the reaction you will decrease the rate of the reaction as well and therefore in industries that use the Haber process for the production of ammonia, the temperature is not too low).

I hope this has helped - if you need to make reference to Kc then you should be stating that the value of Kc changes with temperature but remains constant when any other condition of the reaction is changed.


Thankyou so much this is so helpful x
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