A sports drinks company uses a flame photometer to measure the concentration of sodium ions in its drinks. The flame photometer is first calibrated using standard solutions of known sodium ion concentration.
The table shows the calibration results.
| Concentration of sodium ions / mg dm−3\mathrm{mg\,dm^{-3}}mgdm−3 | 0 | 2.0 | 4.0 | 6.0 | 8.0 | 10.0 |
|---|---|---|---|---|---|---|
| Meter reading | 0 | 16 | 32 | 48 | 64 | 80 |
Give two advantages of using an instrumental method, such as flame photometry, instead of a flame test.
Describe the relationship between the meter reading and the concentration of sodium ions.
A diluted sample of the sports drink gives a meter reading of 36. Determine the concentration of sodium ions in the diluted sample.
The diluted sample was made by diluting the drink by a factor of 10. Calculate the concentration of sodium ions in the undiluted drink.
The label states that the drink contains 50 mg dm−3\mathrm{mg\,dm^{-3}}mgdm−3 of sodium ions. Suggest why a flame test could not be used to check this value.
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.