Pure gold is 24-carat gold. Rings are often made from 18-carat gold, which contains 18 parts gold out of every 24 parts, mixed with other metals.
Which row explains why 18-carat gold is used for rings and gives its percentage of gold?
| Why 18-carat gold is used for rings | Percentage of gold (%) | |
|---|---|---|
| A | The added metals form covalent bonds with gold, so it is harder | 75 |
| B | Atoms of different sizes distort the layers, so they slide less easily | 18 |
| C | Atoms of different sizes distort the layers, so they slide less easily | 75 |
| D | The added metals make the layers more regular, so it is harder | 75 |
A
B
C
D
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.