A technician checks the copper(II) ion concentration in an electroplating bath using flame emission spectroscopy. The technician compares the light intensity from the sample with measurements from standard solutions.
The technician first dilutes 2 cm32\,\mathrm{cm^{3}}2cm3 of the bath sample to 20 cm320\,\mathrm{cm^{3}}20cm3. Then 5 cm35\,\mathrm{cm^{3}}5cm3 of this solution is diluted to 25 cm325\,\mathrm{cm^{3}}25cm3. The intensity measured for the final diluted solution is 40.
| Solution | Concentration of copper(II) ions (mg/dm3\mathrm{mg/dm^{3}}mg/dm3) | Intensity |
|---|---|---|
| Standard 1 | 0 | 0 |
| Standard 2 | 100 | 16 |
| Standard 3 | 200 | 32 |
| Standard 4 | 300 | 48 |
| Standard 5 | 400 | 64 |
Calculate the concentration of copper(II) ions in the original bath sample.
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.