unit 3 - Fertilisers Flashcards
name the three elements essential for plant growth
nitrogen, phosphorus, potassium
give two sources of natural fertilisers
decay of dead plants and animals + decay of plant and animal waste
give two sources of synthetic fertilisers
Haber process - ammonia. Ostwald process - nitric acid
comment on the effect of temperature on the Haber process
low temperature - high yields but very slow. high temperature - low yield but commercially efficient
what does the condenser do in the Haber process
cools the reaction down, making ammonia a liquid, which is easier to extract
state the ideal conditions for the Haber process
450ºC, 200 atmospheres
describe the Haber process
nitrogen (from air) and hydrogen (from methane) are combined in a condenser, iron is then added as a catalyst in the catalyst chamber. the reaction is cooled in a condenser to make the ammonia liquid, allowing it to be removed and collected. the remaining hydrogen and nitrogen can be recycled by being put back into the process
how can nitrate fertilisers be made
neutralisation reactions
why can producing nitric acid be difficult?
nitrogen is very unreactive due to its strong triple bond
describe the Ostwald process
air and ammonia (from Haber process) are passed over a platinum catalyst at 800ºC. this produces nitrogen monoxide which combines with oxygen to form nitrogen dioxide. this can then be dissolved in water to create nitric acid
how is the Ostwald process commercially efficient?
the oxidation of ammonia is exothermic so the temperature stays high in the catalyst chamber
how is the neutralisation of nitric acid with ammonia different from all other neutralisation reactions
no water is produced
