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
Assistance needed.
Please type your subject in the School Subject box. Any other words are likely to delay responses from a teacher who knows that subject well.
To determine which ion is present in the solution, we need to analyze the observations step by step.
From the information provided, we can deduce the following:
1. When a few drops of NaOH (sodium hydroxide) are added to the sample of the unknown, a blue precipitate appears.
This indicates the formation of a metal hydroxide, as metal hydroxides often give characteristic colors when they precipitate out of solution.
2. When approximately 1 mL of ammonia (NH3) is added to the solution, the precipitate dissolves, but the solution remains blue.
This suggests the presence of a transition metal ion, as ammonia is known to dissolve many metal hydroxides, forming complex ions.
Therefore, the presence of a blue precipitate that dissolves upon the addition of ammonia suggests the presence of a transition metal ion, specifically a transition metal hydroxide complex ion.
To determine the specific transition metal ion present, we need to consider the characteristic colors of different metal hydroxides.
Some commonly encountered transition metal hydroxide colors are:
- Copper (Cu): blue
- Cobalt (Co): pink
- Nickel (Ni): green
- Iron (Fe): brown or yellow
Based on the given observations, since the precipitate is blue, and the addition of ammonia causes the solution to still remain blue, we can conclude that the transition metal ion present in the solution is copper (Cu).
To confirm this identification, it is recommended to perform further confirmatory tests or additional analysis techniques based on the specific properties of copper ions.