fertilisers Flashcards
(17 cards)
what does NPK stand for?
nitrogen, phosphorous, potassium
why are fertilisers used?
to improve agricultural productivity
why is nitrogen important?
for cell growth and protein synthesis
why is phosphorous important?
DNA synthesis
why is potassium important?
to make enzymes involved in respiration and photosynthesis
what are NPK fertilisers?
formulations of various salts containing appropriate percentages of the elements
ammonium nitrate equation
ammonia + nitric acid —–> ammonium nitrate
NH3 + HNO₃ —-> NH₄NO₃
why is ammonium nitrate a good compound?
it has nitrogen from two sources
how are fertilisers made in industry?
- reaction is carried out in giant vats, at high concentrations resulting in a very exothermic reaction
- heat released is used to evaporate water from the mixture to make a very concentrated ammonium nitrate product
- continuous process
how are fertilisers made in labs?
- reaction is carried out by titration and crystallisation
- reactants are at a much lower (dilute) concentration than in industry so less heat produced by the reaction so safer as reaction is very exothermic
- after titration, mixture is crystallised to give pure ammonium nitrate crystals
- crystallisation isn’t used in industry as it is very slow
what can be used as a source of potassium?
potassium chloride and potassium sulphate
what is obtained by mining?
- potassium chloride (soluble)
- potassium sulfate (soluble)
- phosphate rock (insoluble)
why can’t phosphate rock by directly used so what instead?
- it is insoluble meaning plants can’t absorb them and use them as nutrients
- treated with nitric or sulfuric acid to produce soluble salts that can be used as fertilisers
what is phosphate treated with to produce soluble salts?
- sulfuric acid
- phosphoric acid
- nitric acid
phosphate equations
- phosphate + nitric acid —> phosphoric acid + calcium nitrate
- phosphate + sulfuric acid —> calcium sulfate + calcium phosphate (single superphosphate)
- phosphate + phosphoric acid —> calcium phosphate (triple superphosphate)
what can the phosphoric acid, produced by phosphate and sulfuric acid be used for?
neutralised by reacting with ammonia to make ammonium phosphate
3 ammonia equations
- ammonia + phosphoric acid —> ammonium phosphate
3NH3 (aq) + H3PO4 (aq) —> (NH4)3 PO4 (aq) - ammonia + sulfuric acid —> ammonium sulfate
2NH3 (aq) + H2SO4 —> (NH4)2 SO4 (aq) - ammonia + nitric acid —> ammonium nitrate
NH3 + HNO₃ —> NH₄NO₃
