A student does a flame test on a solid that contains both sodium ions and potassium ions.
The student sees only a yellow-orange flame.
What is the reason for this?
The yellow-orange colour from the sodium ions hides the lilac colour.
Potassium ions give no flame colour when sodium ions are also present.
Sodium ions react with potassium ions to make a compound with a yellow flame.
Potassium ions give a yellow-orange flame, which is the same as sodium ions.
52 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.