Question

If a metal strip of aluminium is dipped into an aqueous solution of copper sulphate for some time, the surface of the strip becomes brownish. What is the reason for this? Write a balanced chemical equation.

Answer 1

In the activity series of metals aluminum is more reactive than copper.  Thus aluminum can displace copper from it's salt solution.

2Al + 3CuSO4 -------> Al2(SO4)3 + 3Cu

As the reaction proceeds , the blue color of copper sulphate decolourizes  and the solution turns colorless .  this then causes red color copper to deposit on the aluminum strip.