Question

what changes do you observe in the iron nails and colour of copper sulphate sloution. If iron nails are dipped in cuso4 for 15 minutes​

Answer 1

A displacement reaction takes place. Iron displaces copper from it's sulphate and forms green colored solution and brown colored copper.

Fe(gray) + CuSO4(blue) ------> FeSO4(green) + Cu(brown)

Answer 2

If iron nails are put in Copper Sulphate, then you will see that the blue copper sulphate solution turns green and a brownish deposit starts floating on the surface.

Reason: This happens because iron, I being more reactive than copper replaces it in the solution-

CuSO4 + Fe => FeSO4 + Cu