What occurs when sodium hydroxide is added to a solution containing Fe²⁺ ions?

When sodium hydroxide is added to a solution containing Fe²⁺ ions, a reaction occurs that leads to the formation of a green precipitate of iron(II) hydroxide, represented by the chemical formula Fe(OH)₂. This occurs because sodium hydroxide is a strong base that reacts with iron(II) ions in solution. The Fe²⁺ ions combine with hydroxide ions (OH⁻) from sodium hydroxide, resulting in the precipitation of iron(II) hydroxide.

Fe(OH)₂ is known to be insoluble in water and is typically characterized by its green color, which is distinct from the brown precipitate that would form if Fe³⁺ ions were present instead. The formation of this green precipitate is a clear indication that the Fe²⁺ ions are being effectively converted into their hydroxide form.

Understanding this reaction is important as it illustrates how different ions can interact with bases to form precipitates, which is a key concept in inorganic chemistry.