Haber process / NPK fertilisers Flashcards
(16 cards)
what 3 conditions are used in the haber process
iron catalyst
temperatures of about 450 degrees
pressure of 200 atmospheres
how does changing temperature affect haber process
forward reaction is exothermic
-therefore a lower temperature increases yield
-but decreases rate
how does changing pressure affect haber process
fewer gas molecules on product side
-so increasing pressure increases yield
-but decreases rate
(also v expensive to increase pressure)
how does adding a catalyst affect haver process
add iron catalyst
-does not increase yield
-but decreases rate
give reaction in haber process
N2 + 2H2 -> 2NH3
reversible reaction
Define NPK fertilisers
fertilisers are produced industrially to increase amount of food obtained from crops
-compounds containing nitrogen, phosphorus, potassium are used
what can u do with the unreacted nitrogen and hydrogen produced in haber process
recycle them by passing them back over the catalyst
what effect does the catalyst have on position of equilibrium
no effect at all- does not affect yield but does affect rate
what is the main compound of nitrogen in npk fertilisers + how is it produced
Ammonium nitrate
-use ammonia (haber process) to produce nitric acid
-react nitric acid with more ammonia to make ammonium nitrate
where does potassium come from (npk)
potassium chloride OR potassium sulfate
-mined from the ground
-can be used directly without any further processing
where does the phosphorus come from (npk)
-phosphate rock
MUST BE CHEMICALLY PROCESSED BEFORE PUT IN NPK
treating phosphate rock with nitric acid
produces phosphoric acid and calcium nitrate
why cant we add phosphoric acid directly to plants
it must be neutralised with ammonia to produce ammonium phosphate (can be used in npk fertilisers)
treating phosphate rock with sulfuric acid
produces a mixture of calcium phosphate and calcium sulfate
MIXTURE CALLED: SINGLE SUPERPHOSPHATE
-mixture can be used in npk fertilisers
treating phosphate rock with phosphoric acid
produces: TRIPLE SUPERPHOSPHATE
-can be used in npk fertilisers
name 3 acids which can be used to treat phosphate rock
-phophoric acid
-sulfuric acid
-nitric acid
