[AWK]

You should know, at least  basis of qualititative analytical chemistry.
http://fch.upol.cz/skripta/fcc_and_zvem_english/anal/anal_teorie.htm

[Rutherford]

Thanks for the link, I know the basics, but found out something new on the link. The best way to determine Zn²⁺ would be to add sulfide water, because on the link that you gave me it is said that ZnS is the only white sulfide. Only anions left.

[AWK]

There are different procedures for single cations, there are systematic procedure for mixture.
For some mixtures you can use shortcuts, but not for all. In the systematic procedure for mixture the zinc cation may be together with Al3+ and chromate only - then both sulfide and ferrocyanide works.

[Rutherford]

I will be given a salt made from one cation and one anion only, no mixtures.

[Rutherford]

On your like isn't written that Al gives a precipitate with NH₃. In my book it is said that Al gives a white precipitate with NH₄Cl and NH₃ buffer solution and Iron gives a redish-brown precipitate. What is correct?

[AWK]

Even NH₄Cl itself forms Al(OH)₃ from Al salts but in colloidal form almost invisible (solution of Al salts are often additionaly acidified - then nothing happens).
Pure ammonia or ammonia buffer (NH₃/NH₄Cl) forms visible colourless precipitates (often gelatinous).

Iron gives a redish-brown precipitate

correct

[Rutherford]

Ok, thanks.

[Rutherford]

I finished my list, but I have some doubts. Can someone check it if I write it here?