In the qualitative analysis scheme, what qualitative analysis principles are used to separate Cu2+ from Al3+? Check all that apply.

-Selective precipitation
-Fractional precipitation
-Amphoteric precipitate solubilization
-Competitive equilibrium solubilization: anoion protonation
-Competitive equilibrium solubilization:cation complexation
-Selective oxidation/reduction

There are two or three schemes used in qual analysis. I don't know which scheme you used. USUALLY Al is ppted as Al(OH)2 and Cu as CuS. You can take it from there.