An excess of concentrated ammonium hydroxide is a group reagent for the cations of the VI analytical group (acid-base classification) Co2+, N i2+, Cd2+, Cu2+, Hg2+. In this case the following substances are formed:

Answer options

1. Water-soluble ammonia complexes
2. Stained, water-insoluble compounds
3. Hydroxides of alkali-soluble cations
4. Hydroxides of the cations insoluble in the excess of ammonium hydroxide
5. Hydroxides of acid-soluble cations