Here's why:
* Copper(II) ions have a characteristic blue-green color in aqueous solutions. This color arises from the absorption and re-emission of light by the d-electrons in the copper(II) ion.
* Chloride ions (Cl⁻) are colorless in solution.
* The color of the solution is primarily due to the presence of the copper(II) ion.
Therefore, the blue-green color observed in a CuCl₂ solution is a result of the interaction of light with the copper(II) ions.
