Which metal ions can be identified using sodium hydroxide solution?

The identification of metal ions using sodium hydroxide solution is based on the formation of insoluble hydroxides when specific metal ions react with the alkaline solution.

In the case of aluminium, calcium, and magnesium, when sodium hydroxide is added to solutions containing these metal ions, they form distinct precipitates. For example, aluminium forms a white precipitate of aluminium hydroxide, which can dissolve in excess sodium hydroxide to form a soluble aluminate. Calcium hydroxide is formed as a white precipitate, while magnesium hydroxide also appears as a white precipitate, although it is somewhat less soluble. Thus, all three ions can be effectively identified through their characteristic precipitate formation with sodium hydroxide.

The other groups of metal ions listed do not all behave in the same way. Iron and copper react differently with sodium hydroxide; for instance, iron can produce different colored precipitates depending on its oxidation state (e.g., Fe(OH)₂ is green and Fe(OH)₃ is reddish-brown). Zinc reacts to form a white precipitate which is soluble in excess sodium hydroxide, making it less straightforward for identification. Lead forms a white precipitate as well, but it can exhibit complexity related to solubility too. B