Fertilisers (SQA National 5 Chemistry): Flashcards
Exam code: X813 75
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What are fertilisers?
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What are fertilisers?
Fertilisers are substances which restore essential elements to the soil, helping plants to grow healthily.
What are the three essential elements found in NPK fertilisers?
The three essential elements are:
Nitrogen (N)
Phosphorus (P)
Potassium (K)
True or False?
Nitrogen promotes healthy root growth in plants.
False.
Nitrogen promotes healthy leaf growth. It is phosphorus that promotes healthy root growth.
Why must fertilisers be soluble in water?
Fertilisers must be soluble so that they can be absorbed by the plant's roots from the surrounding soil water.
Ammonia solution reacts with an .......... to produce an ammonium .......... and water. These ammonium salts are excellent ..........-rich fertilisers.
Ammonia solution reacts with an acid to produce an ammonium salt and water. These ammonium salts are excellent nitrogen-rich fertilisers.
What is the word equation for producing ammonium nitrate from ammonia solution?
The word equation is:
ammonia solution + nitric acid → ammonium nitrate + water
This is the key industrial reaction for producing a nitrogen-based fertiliser.
True or False?
A potassium deficiency in plants can cause yellow leaves.
True.
Potassium promotes the growth of healthy flowers and fruits, and a deficiency can lead to yellow leaves.
Ammonium phosphate is produced by reacting ammonia solution with .......... acid. It supplies both .......... and .......... to plants.
Ammonium phosphate is produced by reacting ammonia solution with phosphoric acid. It supplies both nitrogen and phosphorus to plants.
How can you identify which essential NPK elements a fertiliser provides from its chemical formula?
Look for the symbols N, P and K in the formula:
N indicates nitrogen
P indicates phosphorus
K indicates potassium
For example, KNO3 contains potassium (K) and nitrogen (N).
What is the Haber process?
The Haber process is an industrial process used to manufacture ammonia (NH3) from nitrogen and hydrogen gas.
What are the reactants and product in the Haber process?
The reactants are nitrogen (from the air) and hydrogen gas. The product is ammonia (NH3). The reaction is reversible:
N2 (g) + 3H2 (g) ⇌ 2NH3 (g)
True or False?
An iron catalyst is used in the Haber process to increase the rate of reaction.
True.
An iron catalyst speeds up both the forward and backward reactions equally, allowing the process to be economical at the compromise temperature.
Why is a compromise temperature used in the Haber process rather than a very high or very low temperature?
A very low temperature gives a high yield but the reaction is too slow to be economical. A very high temperature increases the rate but the backward reaction becomes dominant, giving a low yield. A compromise temperature gives a reasonable rate and a reasonable yield.
In the Haber process, .......... gas and hydrogen gas react reversibly to form ........... An .......... catalyst is used to increase the rate of reaction.
In the Haber process, nitrogen gas and hydrogen gas react reversibly to form ammonia. An iron catalyst is used to increase the rate of reaction.
What is the Ostwald process?
The Ostwald process is the industrial method for producing nitric acid (HNO3) from ammonia, oxygen and water.
What are the reactants and product of the Ostwald process?
The reactants are ammonia, oxygen (from the air) and water. The final product is nitric acid (HNO3).
True or False?
A platinum catalyst is used in the Ostwald process.
True.
A platinum catalyst speeds up the reaction between ammonia and oxygen. Like all catalysts, it is not used up and can be recovered at the end.
How do the Haber and Ostwald processes link together in the production of ammonium nitrate fertiliser?
The Haber process produces ammonia. Some of that ammonia is fed into the Ostwald process to produce nitric acid. Ammonia and nitric acid are then reacted together to make ammonium nitrate.
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