a few drops of NaOH are added to a sample of the unknown. A blue precipitate appears. Next, approximately 1mL of ammonia, NH3, is added. The precipitate dissolves, but the solution remains blue. Which ion is present. Explain

Answer 1

If the color of the original sample was NOT blue, then the ppt with NaOH probably is Cu(OH)2 and the addition of ammonia produces a dark blue solution of Cu(NH3)4^+2. (I don't see a DARK BLUE solution mentioned so I may be taking something for granted here.)