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.

1. Does this reaction absorb or release absorb or release energy? How do you know?
2. What do the color changes indicate?

Answer 1

The reaction has released energy because the temperature of the reaction mixture has risen.

The color changes indicate that the iron displaced copper from the copper sulfate solution, causing it to precipitate and the color of Cu+2 ions to fade.