Study Notes
Fertilisers are compounds containing nitrogen, phosphorus, and potassium used to enhance plant growth and agricultural productivity.
- Ammonium Salts — compounds used as fertilisers to provide nitrogen. Example: Ammonium nitrate is a common fertiliser.
- Nitrates — salts containing nitrogen used in fertilisers. Example: Calcium nitrate is used to supply nitrogen to plants.
- NPK Fertilisers — fertilisers that provide nitrogen, phosphorus, and potassium. Example: A balanced NPK fertiliser might have a ratio of 10-10-10.
- Displacement Reaction — a reaction where ammonia is produced from ammonium salts. Example: NH4Cl + NaOH → NH3 + H2O + NaCl.
Exam Tips
Key Definitions to Remember
- Ammonium salts are compounds used as fertilisers to provide nitrogen.
- Nitrates are salts containing nitrogen used in fertilisers.
- NPK fertilisers provide nitrogen, phosphorus, and potassium.
Common Confusions
- Confusing the role of nitrogen, phosphorus, and potassium in plant growth.
- Misunderstanding the displacement reaction of ammonia from ammonium salts.
Typical Exam Questions
- What elements do NPK fertilisers provide? Nitrogen, phosphorus, and potassium.
- How is ammonia produced from ammonium salts? By a displacement reaction with a strong base.
- Why can't plants absorb nitrogen, phosphorus, and potassium as pure elements? They need these elements in compound form to absorb them.
What Examiners Usually Test
- Understanding of the role of NPK fertilisers.
- Ability to identify compounds that can be used as fertilisers.
- Knowledge of the displacement reaction to produce ammonia.