CAIE A Level Chemistry 9701 · The Periodic Table: chemical periodicity
The table below shows the approximate pH values of the solutions formed when the oxides of the Period 3 elements (from Na to S) are added separately to water.
| Oxide | pH of solution |
|---|---|
| 13 | |
| 10 | |
| 7 | |
| 7 | |
| 2 | |
| 2 | |
| 0 |
Explain the variation in these pH values.
4 marks, so the mark scheme is looking for about 4 separate creditworthy points. Making the same point twice in different words earns it once.
Explain means: Give the reasons or the mechanism: why or how something happens. Link each point to the next with because, so or which means. A list of facts with no links usually loses the reasoning marks.
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