[CopperSulfate]

I am mixing Copper(II)Sulfate and Hydrochloric Acid. When adding a concentration of under 3.0mol/liter (of HCl) it does not change color unless it is heated (the only heating test I have actually done is with 1.0mol/liter and it changed color to green at about 100 degrees). When the concentration is above about 3.0mol/liter (hydrochloric acid) the reaction will turn green which I assume is the Copper(II)Chloride complex. What I don't completely understand is the reason for needing the concentration of the hydrochloric acid to be over about 3mol/liter or heating it to a higher temperature for the Copper(II)Chloride complex to be formed. Thanks!

[Borek]

Honestly - no idea, but what you see is an equilbrium between two complexes - in one ligand is water, in other chlorides. Thus you have full spectra of explanations possible, starting with kinetics of ligand exchange, ending with stability constants.