What are NPK fertilisers?
Why are they useful to manufacture and use?
Fertilisers that contain nitrogen, phosphorous and potassium;
Useful because they increase plant growth and yield;
making farming more productive and profitable;
avoiding fields becoming nutrient poor and unable to grow more plants due to lack of N,P and
What do plants use NPK for? (Biology overlap)
Use nitrogen and phosphorous for making DNA;
nitrogen for making proteins;
potassium for many biochemical processes;
What is the Haber process? What does it produce?
The Haber process is a way of combining nitrogen from the air with hydrogen from natural gas;
forming ammonia;
which can be used to make fertilisers; and explosives; as well as many other chemicals;
How do we obtain the reactants for the Haber process?
Nitrogen is extracted from the air; using fractional distillation;
hydrogen is obtained by reacting methane (CH4) with steam; also produced carbon monoxide;
What salts are made from ammonia that are in fertilisers?
Ammonium sulphate;
ammonium nitrate;
ammonium phosphate;
How can ammonia be made in the lab from one of its salts (E.g. ammonium sulphate)?
Add the ammonium salt to an alkali and warm gently;
e.g. (NH4)2SO4 + Ca(OH)2 ? CaSO4 + 2 NH3 + 2 H2O;
ammonia, calcium sulphate and water produced;
What are the reactions and conditions of the Haber process?
3 volumes of hydrogen reacted with 1 volume of nitrogen gas;
nitrogen + hydrogen ? ammonia
N2(g) + 3H2(g) ? 2NH3(g)
under 450 celsius temperature;
and 200 atm pressure;
using an iron catalyst;
Why are the conditions of the Haber process high temperature and pressure?
Increases rate of reaction;
compromise between higher rate of reaction and increased yield;
yield would be higher at a lower temperature, but it would be slower;
Why are gases recycled in the Haber process?
Because not all of the reactant gases;
nitrogen and hydrogen;
react, therefore they are recycled to increase yield of gases;
What is the contact process?
A reaction that creates sulphuric acid;
using sulfur from the ground (or sulfur ores) and oxygen and water;
What are the uses of sulphuric acid? Why is it so important?
Used to make fertilisers, detergents, plastics, fibres, paints, salts;
without it, many products would not be possible to manufacture;
What are the main stages of the contact process?
Sulfur is reacted with oxygen;
sulfur + oxygen --> sulfur dioxide
S(g)+ O2(g) --> SO2(g)
Then sulfur dioxide + oxygen ? sulfur trioxide.
2SO2(g) + O2(g) ? 2SO3(g)
using a
vanadium (V) oxide catalyst
;
at
450 celsius
;
finally; sulphur trioxide + water -->