International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

What flame color is produced by potassium ions (K⁺)?

1. Yellow

2. Crimson red

3. Lilac

4. Blue

The correct answer is: Lilac

The flame color produced by potassium ions (K⁺) is lilac. This distinctive lilac color occurs due to the energy transitions of the electrons in potassium when they are heated in a flame. When potassium ions are excited by the heat, the electrons absorb energy and jump to higher energy levels. When they return to their original energy levels, they release energy in the form of light. The specific wavelengths of light emitted correspond to the lilac color that is characteristic of potassium. In contrast, other metals produce different flame colors; for example, sodium produces a bright yellow flame due to its electron transitions, while lithium produces a crimson red flame and copper produces a blue-green flame. This unique identification through flame colors is an essential technique used in qualitative analysis in chemistry.