When you add 3 pieces of zinc to blue copper sulfate and hydrochloric acid, a single displacement reaction occurs. The zinc is more reactive than copper, so it displaces copper from the copper sulfate. The reaction can be written as:
Zn(s) + CuSO4(aq) → Cu(s) + ZnSO4(aq)
In the presence of hydrochloric acid, the reaction proceeds as follows:
Zn(s) + CuSO4(aq) + 2HCl(aq) → Cu(s) + ZnCl2(aq) + H2SO4(aq)
In this reaction, zinc (Zn) reacts with copper sulfate (CuSO4) and hydrochloric acid (HCl) to form copper (Cu), zinc chloride (ZnCl2), and sulfuric acid (H2SO4). The copper is seen as a reddish-brown solid precipitate, while the sulfuric acid remains dissolved in the solution.