The flame color observed for K+ in a flame test is which color?

• A. Red
• B. Yellow
• C. Lilac
• D. Blue

Answer: (C)

When atoms are heated in a flame, their electrons get excited and then fall back to lower energy levels, emitting light at specific wavelengths. Potassium has emission lines in the violet region of the spectrum, so the flame looks pale purple—often described as lilac. This lilac color is the clearest visual cue for potassium in a flame test, though it can be faint if sodium or other impurities are present, since sodium’s bright yellow flame can mask it. So the observed lilac color best identifies potassium, whereas red would point to lithium, yellow to sodium, and blue to other elements like copper.