Question

what happens when a piece of

1) zinc metal is added to a copper sulphate solution

2) aluminium metal is added to dil-HCl

3) silver metal is added to copper sulphate solution

Answer 1

1) This is a displacement reaction in which the blue colour of the CuSO₄ solution fades away on reaction with Zinc.
$Zn+CuS{O}_4\to ZnS{O}_4+Cu$
2) $2Al+6HCl\to 2AlC{l}_3+3H_2$
Hydrogen gas is evolved in the process.
3) No reaction because silver is not able to displace copper from the solution. Silver lies below copper in the electrochemical series.