A technician checks a colourless cleaning fluid for contamination by metal ions. The contaminant is known to be one of the following ions: Na+\text{Na}^+Na+, Ca2+\text{Ca}^{2+}Ca2+, Mg2+\text{Mg}^{2+}Mg2+ or Al3+\text{Al}^{3+}Al3+.
Immediately before testing the cleaning fluid, the technician used the same nichrome wire to test a reference solution containing sodium ions. The technician did not clean the wire between the tests.
The results for the cleaning fluid are shown in the table.
| Test | Result |
|---|---|
| Flame test | Yellow flame |
| Sodium hydroxide solution added drop by drop | White precipitate forms |
| Excess sodium hydroxide solution added | The precipitate dissolves |
Give the metal ion contaminating the cleaning fluid. Explain how the results and the way the flame test was carried out lead to your answer.
Describe how the technician should repeat the flame test to obtain a reliable result.
93 exam-style questions on AQA GCSE Chemistry 8.3 Identification of ions by chemical and spectroscopic means, covering 8.3.1 Flame tests, 8.3.2 Metal hydroxides, 8.3.3 Carbonates, 8.3.4 Halides, 8.3.5 Sulfates, 8.3.6 Instrumental methods, and 8.3.7 Flame emission spectroscopy. Each one has a worked solution and a mark scheme showing where the marks go.