Question

How to separate black CuO from a mixture of CuO and ZnO?

Answer 1

Copper oxide is metallic oxide. Metallic oxides are basic and can react with acids. Zinc oxide is an amphoteric oxide. Amphoteric oxide can react with acids as well as base. In order to separate copper oxide from zinc oxide, add sodium hydroxide solution to the mixture. Zinc oxide being amphoteric will react with NaOH to form Na22+[Zn(OH)4]2- whereas copper oxide will remain undissolved. Zinc oxide can be recovered from the solution adding acid to it.