Unit 3-Fertilisers
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What is a fertiliser?
Substances added to soil to provide essential nutrients
Which three essential elements do fertilisers provide?
Nitrogen, phosphorus and potassium (NPK).
Why must fertilisers be soluble?
They must dissolve in water so plants can absorb nutrients through their roots.
What problem occurs if fertilisers are too soluble?
They can be washed into rivers/lakes causing pollution, algal blooms and fish death.
What do ammonia solutions react with to form fertilisers?
Acids
What is the general word equation for making ammonium salts?
Ammonia solution + acid → ammonium salt + water.
What is ammonia like at room temperature?
A pungent, clear, colourless gas.
What happens when ammonia dissolves in water?
It forms an alkaline solution.
What chemical is produced by the Haber process?
Ammonia (NH3)
What are the reactants used in the Haber process?
Nitrogen (N2) and hydrogen (H2)
What is the balanced equation for the Haber process?
N2 + 3H2 ⇌ 2NH3
What does the ⇌ symbol mean?
The reaction is reversible
What temperature conditions are used in the Haber process?
A moderate temperature as a low temperature is too slow and high temperature cause ammonia to decompose
What pressure is used in the Haber process?
High pressure to increase ammonia yield.
What catalyst is used in the Haber process?
Iron
Which chemical is made from ammonia in the Ostwald process?
Nitric acid
What are the reactants in the Ostwald process?
Ammonia, oxygen and water.
What catalyst is used in the Ostwald process?
Platinum.
What is nitric acid used for in fertiliser production?
To make soluble nitrate salts.
What is the word equation for making nitrate fertilisers from nitric acid?
Acid + base → salt + water (neutralisation).