NPK Fertilisers Quiz | GCSE Chemistry (Foundation)

Answer all the questions below to test your knowledge of NPK fertilisers, plant nutrients, nitrate ions, leguminous plants, phosphate rock and superphosphate. Hit the check answers button to get your score.

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

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

1. What is a fertiliser?

a) A substance added to the soil to provide essential minerals for healthy plant growth.
b) A substance that kills plants.
c) A gas in the air that plants breathe in.
d) Any liquid used to water plants.

2. The three main elements in an NPK fertiliser are:

a) Nitrogen, phosphorus and potassium.
b) Sodium, sulfur and chlorine.
c) Carbon, hydrogen and oxygen.
d) Iron, copper and zinc.

3. Most plants cannot use nitrogen gas from the air. Which form of nitrogen do they usually take in from the soil?

a) Nitrogen gas (N₂).
b) Nitrate ions (NO₃^-).
c) Oxygen gas (O₂).
d) Water vapour.

4. In an NPK fertiliser, N stands for , P stands for , and K stands for .

5. Why do farmers add fertilisers to their fields each year?

a) To replace essential minerals removed from the soil when crops are harvested.
b) To make the soil heavier.
c) To cool the soil down.
d) To kill plants that are growing too fast.

Farmer applying a NPK fertiliser to his fields.

6. Leguminous plants such as clover have bacteria in nodules on their roots. What do these bacteria do?

a) They make the plant produce more flowers.
b) They convert nitrogen gas from the air into nitrates the plant can use.
c) They remove all minerals from the soil.
d) They stop the plant taking in water.

7. In a bag of fertiliser labelled 20–10–10, what does this N:P:K ratio tell the farmer?

a) It shows the mass of soil in the bag.
b) It shows the relative amounts of nitrogen, phosphorus and potassium in the fertiliser.
c) It shows the number of seeds to plant.
d) It shows the amount of water in the fertiliser.

8. Phosphate rock is used to make some fertilisers. Why can plants not use phosphate rock directly?

a) It is insoluble in water, so the plant roots cannot take it in.
b) It contains no phosphorus at all.
c) It is a gas.
d) It is already a nitrate fertiliser.

9. 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.

10. In industry, fertilisers are made on a large scale. How does this differ from making them in the school lab?

a) In industry the process is continuous, running 24 hours a day, but in the lab it is a small-scale batch (one-off) process.
b) In the lab the fertiliser is made continuously, but industry only makes one small batch.
c) Industrial processes never use any acids.
d) There is no difference at all.

NPK fertilisers – foundation quiz