Fertilisers - Topic 5 - Paper 1
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What is a fertiliser?
A substance which is applied to soil to supply plants with mineral ions needed for growth
How were fertilisers made in the past?
Made from animal waste (e.g. cow manure)
How are most fertilisers made now?
In factories Formulated fertilisers
What is a formulated fertiliser?
A mixture of different chemical compounds, carefully combined in specific ratios, to provide plants with essential nutrients for growth A formulation is a mixture that has been designed as a useful product.
What does NPK stand for?
Nitrogen (N) Phosphorus (P) Potassium (K) The three main elements fertilisers mainly consist of, as plants need these from the soil. NPK fertilisers are formulations of various salts containing appropriate percentages of these three elements.
Why is nitrogen important to plants?
Required to make amino acids and hence proteins, which are essential for growth
What is the main source of nitrogen in fertilisers?
Ammonia Which is made in the Haber Process
How can ammonia be used to make nitric acid?
Ammonia can react with oxygen and water in a series of reactions to make nitric acid
How can ammonia be used to make ammonium salts?
Ammonia can react with acids (including nitric acid) to form ammonium salts. All ammonium salts are soluble in water
What is the difference between ammonia and ammonium?
Ammonia (NH3) Ammonium (NH4) The extra hydrogen on ammonium gives it a +1 positive charge, unlike the neutral ammonia
What are NPK fertilisers?
Fertilisers which provide plants with salts of nitrogen (N), phosphorus (P) and potassium (K)
Why must fertiliser compounds be soluble in water?
So they can be absorbed by the plants root hair cells All nitrates are water soluble All potassium and ammonium salts are water soluble (SPA salts)
Give 2 sources of soluble nitrogen
Ammonium ions, NH4+ Nitrate ions, NO3-
Name a source of soluble phosphorus
Phosphate ions, (PO4)3-
Give the symbol for potassium ions
K+ All common potassium compounds dissolve in water to produce potassium ions This is why potassium is used in compounds in fertilisers - so the plants root hair cells can absorb the dissolved potassium
How is nitric acid made?
Nitric acid is made from ammonia Ammonia + oxygen → nitric acid + water NH3(g) + 2O2(g) → HNO3(aq) + H2O(l)
How can ammonium nitrate be manufactured?
By reacting ammonia solution with nitric acid Ammonia + nitric acid → ammonium nitrate NH3(aq) + HNO3(aq) → NH4NO3(aq) A salt is the substance formed when a hydrogen ion in an acid is replaced by a metal ion
Give the formula for nitric acid
HNO3
How can potassium fertiliser be produced?
Potassium chloride and potassium sulphate can both be mined from the ground and then used directly in fertilisers Potassium fertiliser is the simplest of all the NPK fertilisers to produce.
NPK fertilisers are formulations of different salts. Explain what is meant by the term ‘formulation’.
A formulation is a mixture made from a specific ratio of chemicals To ensure that the product has the required properties