the haber process Flashcards
the haber process
used to manufacture ammonia
what can ammonia be used to produced?
nitrogen-based fertilisers such as ammonium nitrate
word + symbol equation
nitrogen + hydrogen ⇌ ammonia
N2(g)+3H2(g) ⇌ 2NH3(g)
source of nitrogen + hydrogen
nitrogen: obtained easily from the air as it is 78% nitrogen
hydrogen: from reacting methane with steam to form hydrogen and carbon dioxide
state the conditions
temp: 450°C
pressure: 200 atm
catalyst: iron
describe the haber process
the purified gases are passed into a reaction vessel with an iron catalyst at 450°C and a pressure of 200 atm in a 3:1 ratio (H:N)
some of the hydrogen and nitrogen reacts to form ammonia
the reaction is reversible so some of the ammonia produced breaks down into nitrogen and hydrogen
on cooling, the ammonia liquefies and is removed, the remaining hydrogen and nitrogen are recycled back to the start of the process
what does the reaction eventually reach + why?
dynamic equilibrium as the reaction is reversible
what is the ammonia formed as?
a gas but it cools in the condenser so liquifies and is removed
why is the haber process so important?
why is the haber process so important?
what type of reaction is the forward reaction + meaning in terms of yield?
exothermic
so increasing temperature will move the equilibrium away from ammonia and towards nitrogen and hydrogen
because endothermic reaction is favoured to decrease temperature
so yield of ammonia is greater at a lower temperature
however lower temperatures mean a slower rate of reaction
450°C is a compromise between maximum yield and speed of reaction
how does pressure affect the reaction?
-higher pressure moves the position of equilibrium towards the products since there are four molecules of gas on the left-hand side for every two molecules on the right
-so increasing pressure maximises percentage yield
-also increases rate of reaction
-so the pressure is set to as high as possible, without making the process too expensive or too dangerous to build and maintain
how does iron catalyst affect the reaction?
-it increases the rate of reaction by providing an alternative pathway with a lower activation energy
-doesn’t affect the yield
