At a metal-finishing factory, a used cleaning bath is passed through a treatment unit. Flame emission measurements are made before and after treatment. The reference data and both sets of measurements were recorded under the same conditions.
| Reference metal ion | Wavelengths of lines (nm) |
|---|---|
| Sodium ions | 330, 589 |
| Potassium ions | 404, 766, 770 |
| Calcium ions | 423, 616, 644 |
| Cleaning bath | Wavelengths of lines (nm) |
|---|---|
| Before treatment | 330, 423, 535, 589, 616, 644 |
| After treatment | 404, 766, 770 |
Give the names of all the metal ions that can be identified in the cleaning bath before treatment. Suggest what the line at 535 nm535\,\text{nm}535nm shows.
A manager claims that the treatment has removed every metal ion that was present before treatment and has not introduced any other metal ion. Evaluate this claim using the data.
107 exam-style questions on OCR GCSE Chemistry 4.2 Identifying the products of chemical reactions, covering 4.2.1 Tests to identify gases, 4.2.2 Tests for aqueous ions and flame tests, and 4.2.3 Instrumental methods of analysis. Each one has a worked solution and a mark scheme showing where the marks go.