Question

If a strip of aluminium with clean surface is dipped into an aqueous solution of copper sulfate for sometime the surface of the strip becomes brown. Give reason. Write the balanced equation for the reaction

Answer 1

Aluminium is more reactive than copper and so is placed above copper in the reactivity series. Thus, when a strip of aluminium metal is placed in copper sulphate solution, it will displace copper from CuSO4 and form aluminium sulphate and copper metal. Hence the blue colour of the solution will fade away, and copper (which has a reddish brown appearance) will be deposited on aluminium strip. Following is the chemical equation for the reaction

 2Al + 3CuSO4 → Al2(SO4)3 + 3Cu

Answer 2

When a strip of aluminium is dipped into an aqueous solution of copper sulphate it will displace copper and forms aluminium sulphate. Copper will deposit on the surface of aluminium strip so that it will become brownish.

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