Fertilisers

Essential Elements in Fertilisers

Plants need certain elements from the soil to grow properly. The three main essential elements found in fertilisers are:

1. Nitrogen (N)
2. Phosphorus (P)
3. Potassium (K)

Why are these elements important?

If plants don't get enough of these elements, it affects their growth and life processes.

Fertilisers supply these essential elements when they are missing from the soil, or provide more to:

• Increase crop yield
• Produce bigger crops
• Promote faster growth

Ammonia in Fertilisers

• Ammonia (NH₃) is an important chemical used to produce nitrogen-containing compounds for fertilisers.
• Ammonia can undergo a series of reactions with oxygen and water to produce nitric acid.
• Ammonia can also react with acids, such as nitric acid or phosphoric acid, to produce ammonium salts, which are used in fertilisers.

Producing Ammonium Sulfate (Small Scale in the Lab)

Ammonium sulfate (NH₄)₂SO₄ is a nitrogen-rich fertiliser that can be made in a lab using ammonia and dilute sulfuric acid.

Raw Materials:

• Ammonia is produced via the Haber Process.
• Sulfuric acid is produced via the Contact Process. The industrial production of ammonium sulfate is much larger and more complex than the lab method.

Industrial Method:

1. Ammonia gas is introduced into a large reaction chamber.
2. Sulfuric acid is sprayed into the chamber.
3. The ammonia reacts with sulfuric acid to produce ammonium sulfate powder.

• Rates of Reaction: The industrial process is designed for high efficiency and speed, while the lab method is slower and more controlled.
• Reversible Reactions and Equilibrium: The Haber Process and Contact Process involve reversible reactions that are influenced by factors such as temperature and pressure.
• Atom Economy and Yield: The industrial process aims for high atom economy (minimal waste) and maximises yield to ensure cost-efficiency.
• Availability of Raw Materials: On an industrial scale, large amounts of ammonia and sulfuric acid are required, while the lab method only needs small quantities.
• Energy Use: Industrial processes require more energy, especially for the high temperatures and pressures in the Haber and Contact processes.