In Nesslerization for ammonia, the reaction of ammonium with dipotassium mercuric iodide yields which color?

• A. Yellow orange (NeYo)
• B. Blue
• C. Green
• D. Red

Answer: (A)

Nesslerization detects ammonia by the reaction of ammonium with Nessler's reagent in strongly alkaline solution to form a mercuric-ammine complex that yields a colored solution. This complex absorbs light to give a yellow-orange color, and the shade is related to the amount of ammonia present—the more ammonia, the deeper the yellow-orange. That’s why the correct description is yellow orange. The other colors don’t come from this reaction; blue, green, or red would be associated with different reagents or metal ion tests, not Nesslerization with ammonia.