A manufacturer tests how different conditions affect uncoated iron fasteners during transport.
Identical fasteners are kept at the same temperature for 30 days. The table shows the mean percentage of each fastener's surface covered by rust.
| Container | Oxygen reaches the iron | Film of water on the iron | Salt dissolved in the water | Surface covered by rust after 30 days (%) |
|---|---|---|---|---|
| A | yes | no | no | 0 |
| B | yes | yes | no | 16 |
| C | yes | yes | yes | 58 |
| D | no | yes | yes | 0 |
Explain the pattern in the results.
Before transport in container C, the fasteners are coated completely with grease. During transport, the grease is rubbed away from a small area on some fasteners.
Explain how the grease affects where rust forms and the rate of rusting.
136 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.