UNIT 3 - Fertilisers
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what do plants do when they grow?
they extract nutrients from the soil via their roots
what happens to plants over time?
the level of nutrients that they contain decreases and the nutrients need to be replaced in order to grow healthy crops.
what elements are essential for healthy plant growth?
the elements nitrogen, potassium, and phosphorus (NPK)
what are the fertiliser compounds for nitrogen?
nitrates & ammonium salts
what are the fertiliser compounds for phosphorus?
phosphates
what are the fertiliser compounds for potassium?
potassium salts
what must the fertiliser compounds be and why?
they must be soluble in water so that they can be taken up by the plant roots into the plant
what does Δ stand for in the Haber process?
change in enthalpy
what is the Haber process?
the industrial production of ammonia from nitrogen and hydrogen using an iron catalyst
what is the word equation for the Haber process?
N₂ + 3H₂ <—> 2NH₃ ΔH = -92kJ
why can true equilibrium not be achieved in the Haber process?
because it is a true open system
what type of process is the Haber process?
a continuous process
what does the catalyst do in the Haber process?
it provides a fast reaction rate and reasonable yield at lower temperature
what is the rate of reaction like at low temperatures in the Haber process?
at low temperatures the forward rate of reaction is too slow to be economical
what is the rate of reaction like at high temperatures in the Haber process?
at higher temperatures the rate of reaction increases but favours the reverse reaction
what does high pressure favour in the Haber process?
it favours ammonia production but the required equipment is costly to build and maintain
what must be reached in the Haber process?
compromises must be reached between the competing factors
what does maximum yield require in the Haber process?
high pressure and low temperature
how is the Haber process made cost-effective?
by using 200 atmospheres, 400°C and an IRON CATALYST, giving it a 15% yield
how is a 98% yield achieved in the Haber process?
the ammonia produced is condensed and the unreacted gasses are recycled
what are the starting materials in the Ostwalt process?
ammonia, oxygen and water
what is manufactured in the Ostwalt process?
nitric acid
how is a 98% yield achieved in the Ostwalt process?
by using a PLATINUM CATALYST
how many tons of nitric acid are produced annually and for what purpose in the Ostwalt?
sixty million tons are produced for the manufacturing of explosives and fertilisers