What colour precipitate do iron (II) ions produce when reacted with sodium hydroxide solution?

When iron (II) ions react with sodium hydroxide solution, they produce a green precipitate known as iron (II) hydroxide, represented by the chemical formula Fe(OH)₂. This reaction is a classic example of a precipitation reaction, where the soluble ions form an insoluble compound, leading to the formation of this colored precipitate.

In this reaction, the iron (II) ions in solution gain hydroxide ions from the sodium hydroxide, resulting in the formation of the iron (II) hydroxide precipitate. The distinct green color is characteristic of iron (II) compounds, and it helps in visually identifying the presence of iron (II) ions in a solution.

Other colors mentioned in the options, such as blue, red, and black, are not associated with the reaction of iron (II) ions and sodium hydroxide. Blue can be indicative of copper(II) hydroxide, red is typically associated with iron (III) hydroxide, and black might reference ferrous sulfide or other specific iron compounds, but none of these apply in the context of this particular reaction involving iron (II) ions.