3.3 Fertilisers Flashcards
Why do we need fertilisers?
There are too many people to feed with too few plants if we do not fertilise the plants
Why do plants need fertilisers?
Fertilisers restore nutrients (which are essential for plant growth) to the soil
What three elements do fertilisers contain?
NPK (Nitrogen, Potassium, and Phosphorous)
Why is ammonia needed?
Ammonia is the most cost effective way to obtain nitrogen for use in fertilisers
How is ammonia made industrially (and what is the name of this process)?
The Haber process is used to produce ammonia industrially by combining nitrogen and hydrogen at a very high temperature
What is the equation for the Haber process?
N2 (g) + 3H2 (g) {makes a reversible reaction} 2NH3 (g)
What catalyst is used in the Haber process?
Finely divided iron
What is formed when ammonia solutions react with acid?
A soluble ammonium salt (ammonia solution + acid —-> ammonium salt + water)
What is the Ostwald process?
The use of ammonia, oxygen, and water to make nitric acid
What catalyst is used in the Ostwald process?
Platinum
What property is key for fertilisers?
They must be soluble in water
What pH is ammonia solution?
It is a weak alkali (pH 9)
Why isn’t the temperature of the Haber process higher?
At higher temperatures, the reverse reaction occurs more so the overall production of ammonia becomes less eficient
