Fertilisers Quiz | GCSE Chemistry (Higher Tier)

Answer all the questions below to test your knowledge of NPK ratios, specific fertiliser salts, neutralisation equations, phosphate rock reactions, superphosphate and industrial fertiliser production. Hit the check answers button to get your score.

Plants need to take in a variety of soluble minerals from the soil to stay healthy.

Image shows a plant that has been fed an NPK fertiliser and one that has not.

1. Which statement best describes the main roles of nitrogen, phosphorus and potassium in plants?

a) Nitrogen for roots, phosphorus for leaves, potassium for flowers.
b) Nitrogen for healthy leaves and stems, phosphorus for strong roots, potassium for disease resistance and overall health.
c) Nitrogen for flowers only, phosphorus for root hairs, potassium has no clear role.
d) Nitrogen for fruit, phosphorus for seeds, potassium for chlorophyll.

2. A field of wheat shows very slow growth and pale yellow leaves, but the roots appear normal. Which nutrient is most likely in short supply?

a) Potassium (K).
b) Nitrogen (N).
c) Phosphorus (P).
d) Calcium (Ca).

3. Why are many fertilisers made from soluble ionic compounds such as ammonium nitrate or potassium sulfate?

a) Because insoluble compounds would drain out of the soil more quickly.
b) Because soluble ionic compounds dissolve in soil water to release ions that plant roots can absorb.
c) Because only ionic compounds contain any nitrogen.
d) Because soluble ionic compounds cannot move through the soil.

4. Complete the formulae for three common fertiliser salts:
(a) Ammonium nitrate:
(b) Ammonium sulfate:
(c) Potassium sulfate: .

5. Which equation correctly represents the neutralisation reaction used to make ammonium nitrate fertiliser in the lab?

a) NH₃(aq) + HNO₃(aq) → NH₄NO₃(aq)
b) NH₃(aq) + HNO₃(aq) → NH₃NO₃(aq) + H₂O(l)
c) NH₄NO₃(aq) → NH₃(aq) + HNO₃(aq)
d) NH₃(g) + O₂(g) → NO₂(g) + H₂O(l)

Farmer applying NPK fertiliser to his fields.

6. Superphosphate fertiliser (a mixture of calcium sulfate and calcium phosphate compounds) is made by reacting phosphate rock with:

a) Phosphoric acid.
b) Nitric acid.
c) Sulfuric acid.
d) Hydrochloric acid.

7. Which reaction produces calcium nitrate and phosphoric acid from phosphate rock?

a) Phosphate rock + sulfuric acid → calcium sulfate + calcium phosphate
b) Phosphate rock + nitric acid → calcium nitrate + phosphoric acid
c) Phosphate rock + phosphoric acid → triple superphosphate
d) Phosphate rock + water → calcium nitrate + phosphoric acid

8. Triple superphosphate is described as a “more concentrated” phosphate fertiliser than ordinary superphosphate. What does this mean?

a) It is always a liquid rather than a solid.
b) Each tonne contains a higher percentage of phosphorus compounds, so more phosphorus per kilogram of fertiliser.
c) It contains no calcium at all.
d) It has a lower N:P:K ratio.

9. A gardener has two fertilisers:

Fertiliser A: NPK 30–5–5
Fertiliser B: NPK 5–10–10

Which fertiliser would be most suitable for leafy vegetables such as lettuce and spinach?

a) Fertiliser A, because it is higher in nitrogen to promote leaf growth.
b) Fertiliser B, because it has more phosphorus for flowers.
c) Either, because all NPK fertilisers are identical.
d) Neither, because NPK fertilisers are only for root crops.

10. A 40 kg bag of fertiliser is labelled 10–5–10. This means it is 10% nitrogen by mass. How many kilograms of nitrogen does the bag contain?

a) 2 kg
b) 3 kg
c) 5 kg
d) 4 kg

Fertilisers – higher tier quiz