Topic 11 - 11.1 - Fertilisers

Question 1

List the 3 essential elements for plant growth

Answer 1

1. Nitrogen (N₂)
2. Phosphorous (P)
3. Potassium (K)

• Plants can only access nutrients in a soluble form
• Different plants need different levels of each nutrient

Question 2

Name and describe the 2 types of fertiliser

Answer 2

1. NATURAL
* Decay of dead plants and animals
* Decaying animal waste
* Guano (bird and bat poo)

2. SYNTHETIC
* Produced through neutralisation reactions
* Ammonia and Nitric acid are made at the same chemical plant and are reacted together to produce ammonium nitrate (ammonium salts) - it is a very soluble salt with a high N₂ content

Question 3

Describe basic key information about Ammonia

Answer 3

• Nitrogen Trihydride
• Weak base
• NH₃ (covalently bonded)
• Colourless, highly irritating gas at room temp

Question 4

Describe how ammonia can be made in a lab

Answer 4

Ammonium salt is heated with an alkali e.g. Sodium Hydroxide or solid base (soda lime)

Question 5

Describe what happens when ammonia dissolves in water

Answer 5

Ammonium Hydroxide (alkaline solution) is formed - turns pH paper blue

Question 6

Describe the reaction of ammonia with acids

Answer 6

• Ammonia reacts with acids to form ammonium salts

e.g. NH3(g) + HNO3(aq) → NH4NO3(aq)

e.g. (lab method) NH4OH(aq) + HNO3(aq) → NH4NO3(aq) + H2O(l)

(ammonia is an acid and a base, but can only produce a salt when reacting with an acid. ammonium hydroxide can fully neutralise an acid due to its higher OH- content.)