Question

An iron nail (Fe) is placed into a solution of copper(II) sulfate (CuSO4). After some time, the blue color of the copper(II) sulfate disappears and some copper-colored solid (Cu) is found on the surface of the nail. The solution now contains iron(II) sulfate (FeSO4), and the container feels warmer than before the reaction. What do the color changes indicate?

Answer 1

It means the copper ion in solution is almost gone. It's now copper metal precipitating due to the iron from the nail taking it's place on the sulfate. You know have copper solid and FeSO4. FeSO4 is clear I believe.