Iron metal is immerse in the 0.1M CuSO 4 solution. The zinc metal is coated with dark-black elemental copper. The copper metal, however, has no reaction with the ZnSO 4 solution. The iron metal is coated with red-bronze metallic copper. Oxidation occurs when the oxidation number of an atom becomes larger.
Reduction occurs when the oxidation number of an atom becomes smaller.
Oxidizing agents gain electrons while reducing agents lose electrons. In the first reaction, the copper ion is able to oxidize the zinc metal. However, in the second reaction, the zinc ion is not able to oxidize the copper metal. Zinc is a better reducing agent than copper. Strong reducing agents have weak conjugate oxidizing agents.