A flame photometer is calibrated using standard solutions of potassium ions.
| Concentration of potassium ions in mg dm−3\mathrm{mg\,dm^{-3}}mgdm−3 | 0 | 5.0 | 10.0 | 15.0 | 20.0 |
|---|---|---|---|---|---|
| Reading | 0 | 12 | 24 | 36 | 48 |
Sample A gives a reading of 30. Sample B gives a reading of 66.
Statement 1: sample A contains 12.5 mg dm−3\mathrm{mg\,dm^{-3}}mgdm−3 of potassium ions
Statement 2: sample B can be reported reliably as 27.5 mg dm−3\mathrm{mg\,dm^{-3}}mgdm−3, because the readings are proportional to concentration
Statement 3: a flame test by eye could show that potassium ions are present, but not their concentration
Which statements are correct?
1 only
1 and 2 only
2 and 3 only
1 and 3 only
35 exam-style questions on Edexcel GCSE Chemistry 10.1 Qualitative analysis: tests for ions, covering 10.1.1 Principles of ion tests and flame tests, 10.1.2 Tests for cations and for ammonia, 10.1.3 Tests for anions, 10.1.4 Identification of ions in unknown salts, and 10.1.5 Instrumental methods of analysis. Each one has a worked solution and a mark scheme showing where the marks go.