Copper sulphate solution is blue in colour. When powdered zinc is added to it, the solution turns colourless due to the formation of zinc sulphate solution.
Here, the reaction is:
CuSO4(aq) + Zn(s) → ZnSO4(aq) + Cu(s)
Iron reacts with hydrochloric acid to form ferrous chloride and releases hydrogen gas.
Fe (s)+2HCl (aq)→FeCl2(aq)+H2(g)
The reaction between silver nitrate and sodium chloride is a precipitation reaction in which an insoluble precipitate of silver chloride is formed.
AgNO3(aq)+NaCl (aq) →NaNO3(aq) +AgCl(s)