MAJOR HELP: What cation does the solution contain

1. A solution which contains only one of the following cations: Mg2+, Pb2+, or NH4 + is tested with various reagents and the following results are obtained:
Reagent Results
0.2M Na2SO4 precipitate
0.2M Na2S precipitate
0.2M NaNO3 no precipitate
Which cation does the solution contain?

2. A solution which contains only one of the following cations: Ca2+, Cu+, or Sr2+ is tested with various reagents and the following results are obtained:
Reagent Results
0.2M Na2SO4 no precipitate
0.2M NaBr precipitate
0.2M NaNO3 no precipitate
Which cation does the solution contain?

1. lead(II) ion precipitates withy sulfate and sulfide ions
2. Calcium ion form no ppt. with sulfate or bromide (Sr^2+ does): (Cu^1+ forms a ppt with Br-)