Question

When ethane-1,2-diamine is progressively added to aqueous solution of Nickel (II) chloride, the sequence of colour change observed will be:

Hint:

The colour changes in coordination complexes depend on the nature of the ligands and their coordination with the metal center. Ethane-1,2-diamine is a bidentate ligand, which can lead to multiple distinct complexes.

Answer 1

When ethane-1,2-diamine (which is a bidentate ligand) is progressively added to an aqueous solution of Nickel (II) chloride, it forms a series of coordination complexes. The colour changes are characteristic of the formation of these complexes. - Initially, the solution has a pale blue colour, corresponding to the \( \text{NiCl}_2 \) complex. - Upon adding ethane-1,2-diamine, the colour changes to blue due to the formation of a tetrahedral complex. - Further addition of ethane-1,2-diamine results in the formation of green and eventually violet complexes, as the ligand further coordinates with Nickel (II), forming different coordination environments. Thus, the sequence of colour changes is: Pale Blue \( \to \) Blue \( \to \) Green \( \to \) Violet.