A technician tests a sodium compound using a nichrome wire and observes a yellow flame. Without cleaning the wire, the technician then tests a calcium compound. The calcium compound should produce an orange-red flame, but only a yellow flame is observed.
Why is the orange-red flame not observed?
The negative ion in the calcium compound produces a yellow flame instead of the calcium ions.
Heating the nichrome wire twice causes the wire to produce a yellow flame without any ions.
The calcium ions initially produce a yellow flame before changing to an orange-red flame.
The sodium ions remaining on the wire produce a strong yellow colour that masks the orange-red colour from calcium ions.
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.