Why did the color of copper(II) sulfate, CuSO4 changed upon adding hydrochloric acid, HCl?

Question

Why did the color of copper(II) sulfate, CuSO4 changed upon adding hydrochloric acid, HCl?

Answer 1

Sorry but the result is a no visible reaction

Answer 2

Actually your observation is correct. The hydrochloric acid causes the copper(II) ion which is normally attached to 4 water molecules as the blue Cu[H2O]4 2+ complex ion (tetraaquacopper(II)) to change into the green CuCl4 2- complex ion (tetrachlorocopper(II)). If you add more water the equilibrium shifts returning the colour to the normal blue of the water based complex ion.

Hope this helps.