Table 1: Identifying cations in a solution
|
Step |
Action |
Observation |
Possible Explanation |
|
1 |
Add NaOH solution (Procedure 1) |
No ammonia production |
NH⁺ is ruled out |
|
2 |
Add 6 M HCl (Procedure 2) |
White precipitate |
Potential presence of Ag⁺ or Pb²⁺ or both |
|
3 |
Separate the precipitate from the supernatant. Add deionized water to the precipitate and heated it. (Procedure 3) |
No change |
The precipitate is AgCl which confirms the presence of Ag⁺ |
|
4 |
Add NaOH solution to the supernatant from step 3. Separate the precipitate from the supernatant (Procedure 6) |
Green precipitate |
The presence of Ni²⁺ is likely because of the color; Mn²⁺, Fe³⁺, Al³⁺ are possible |
|
5 |
Add H₂SO₄ to the supernatant from step 4 (Procedure 11) |
No change |
Al³⁺ can be ruled out |
|
6 |
Add NH₃ solution to the precipitate from step 4 (Procedure 7) |
Blue solution forms. All precipitate dissolves |
The presence of Ni²⁺ is confirmed, Mn²⁺ and Fe³⁺ are ruled out |