The dilute solution is light blue
The concentrated solution is light green
Reason: the inner color of copper chloride is yellow green in very concentrated solution, while it is green in concentrated solution and blue in dilute solution. The yellow green is due to the presence of [cucl4] 2 + ions, and the blue is due to the presence of [Cu (H2O) 6] 2 + ions. Anhydrous copper chloride is brown yellow. When copper chloride is dissolved in water, a large amount of copper ions and chloride ions are ionized in the aqueous solution.
Generally, Cu2 + in aqueous solution is actually in the form of hydrated ion [Cu (H2O) 4] 2 +, which is blue, so most of our common copper salt solutions are blue. In the solution of copper chloride, there are not only hydrated copper ion [Cu (H2O) 4] 2 +, but also tetrachloride copper complex ion [cucl4] 2 -. The color of the ion is yellow.
According to the optical principle, we know that the mixed color of blue and yellow is green, which is the reason why our common concentration of copper chloride solution is green. If we add water to the copper chloride solution, the concentration of chloride ion in the solution will decrease and the hydrated copper ion will increase relatively. The solution will mainly show the color of hydrated copper ion (blue). So the dilute solution of copper chloride we see is generally blue.