Question

Name a solution that will separate the components of the following mixtures:
(a) Zn(OH)₂ from Pb(OH)₂
(b) CaO from PbO
(c) CuO from ZnO

Answer 1

(a) The separation of Zn(OH)₂ from Pb(OH)₂ can be done by adding excess of ammonium hydroxide solution. On adding excess of ammonium hydroxide, zinc hydroxide forms a soluble, colourless complex, while lead hydroxide remains insoluble.

(b) The separation of CaO and PbO can be done by adding sodium hydroxide solution. On reacting with sodium hydroxide, PbO, being amphoteric in nature, forms soluble, colourless sodium plumbite, while CaO, being basic in nature, shows no reaction.

(c) CuO and ZnO ​can be separated by adding sodium hydroxide solution. On reacting with sodium hydroxide, ZnO, being amphoteric in nature, forms soluble, colourless sodium zincate, while CuO, being basic in nature, shows no reaction.