Question

How will you distinguish between copper and magnesium hydroxide using NH₄OН?

Answer 1

You can distinguish between copper hydroxide [Cu(OH)₂] and magnesium hydroxide [Mg(OH)₂] by adding excess NH₄OH (ammonium hydroxide).

• Copper hydroxide: Dissolves in excess NH₄OH and forms a deep blue solution due to the formation of the tetraamminecopper(II) complex.
• Magnesium hydroxide: Does not dissolve in NH₄OH and remains as a precipitate.

Therefore, the deep blue solution indicates Cu(OH)₂, while the unchanged precipitate indicates Mg(OH)₂.