Qualitative Analysis Help

[avila724]

Question # 1
When a solution containing an unknown number of metal ions is treated with dilute HCl, no precipitate forms. The pH is adjusted to about 1, and H₂S is bubbled through. Again no precipitate forms. The pH of the solution is then adjusted to about 8 and treated with (NH₄)₂S. This time a precipitate forms. The filtrate from this solution is not tested. Which groups of metal ions are either known to be present or cannot be excluded?


A. Group III and Group IV
B. Group III only
C. Group II and Group IV
D. Group IV only
E. Group I and Group IV

Question # 2
In the course of various qualitative analysis procedures, the following mixture is encountered: Na+ and K+. Suggest how this mixture might be separated. You may need to refer to Table 4.1 from Zumdahl.


A. add dilute HCl
B. add 0.2 M HCl and H₂S
C. add (NH₄)₂S at pH 8
D. add (NH₄)₂HPO₄ to a basic solution
E. It is not possible to separate the ions using any reaction scheme found in either Zumdahl or your lab manual.


I got D for #1 because the rest will precipitate but then I'm thinking E because only some of the group I ions will precipitate.

For #2 I got E, its not possible because they are always soluble.

Can anyone help?