The table shows information about four nitrogen fertilisers.
| Fertiliser | Percentage of nitrogen by mass (%) | Cost per tonne of fertiliser (£) |
|---|---|---|
| Ammonium nitrate | 35 | 300 |
| Ammonium sulfate | 21 | 200 |
| Potassium nitrate | 14 | 500 |
| Urea | 46 | 420 |
Which fertiliser provides nitrogen at the lowest cost per tonne of nitrogen?
Ammonium nitrate
Ammonium sulfate
Potassium nitrate
Urea
61 exam-style questions on OCR GCSE Chemistry 6.1 Improving processes and products, covering 6.1.1 Extracting metals industrially and by electrolysis, 6.1.2 Life cycle assessment and recycling, 6.1.3 Biological methods of metal extraction, 6.1.4 The Haber process and the production of fertilisers, 6.1.5 Alloys and their uses, 6.1.6 Corrosion and its prevention, 6.1.7 Comparing and selecting materials, and 6.1.8 Industrial conditions, rate and position of equilibrium. Each one has a worked solution and a mark scheme showing where the marks go.