Which of the following tests can you identify K+ in a salt? — Qualitative and Quantitative Analysis Chemistry Question

💡 Solution & Explanation

Step 1: Potassium ions (K+) give a characteristic lilac/violet color in the flame test when viewed through a cobalt blue glass (or directly). Step 2: In solution, K+ reacts with sodium cobaltinitrite, Na3[Co(NO2)6], to form a bright yellow precipitate of potassium sodium cobaltinitrite, K2Na[Co(NO2)6]. Step 3: Therefore, the combination of a violet flame test and a yellow precipitate with sodium cobaltinitrite identifies K+, matching option (a).