Copper Reduction Reaction
Difficulty: Easy | Time: 10 minutes | Visual Impact: High
Historical Context
Metal displacement reactions have been known since antiquity. Ancient metalworkers noticed that iron tools left in copper-containing waters became coated with copper - a phenomenon called “cementation.” This process was used commercially to extract copper from mine drainage water.
The reactivity series of metals was formalized in the 19th century, explaining why some metals displace others from solution. Iron’s position above copper means iron atoms readily give up electrons to copper ions, reducing them to copper metal while iron dissolves as ions.
This reaction is fundamentally the same chemistry used in electroless plating and has industrial applications in metal finishing and copper recovery from waste streams.
Materials
- Copper sulfate - 10g
- Water - 100mL
- Iron nail (clean, sanded) or steel wool - small pad
- Beaker - 150mL
Procedure
- Dissolve 10g copper sulfate in 100mL water (deep blue solution)
- Sand the iron nail to expose fresh metal surface
- Place nail in solution and observe
- Within 2-5 minutes, copper metal deposits on nail (reddish-brown coating)
- After 30 minutes, solution noticeably lighter as copper is removed
Reaction
\[\ce{Fe + CuSO4 -> FeSO4 + Cu}\]
Or in ionic form: \[\ce{Fe(s) + Cu^{2+}(aq) -> Fe^{2+}(aq) + Cu(s)}\]
The Science
Iron is more reactive than copper, so it displaces copper from solution. This demonstrates the metal reactivity series:
- Iron atoms lose 2 electrons (oxidation): Fe → Fe²⁺ + 2e⁻
- Copper ions gain those electrons (reduction): Cu²⁺ + 2e⁻ → Cu
- Electrons transfer directly where the metals touch
The blue color fades because Cu²⁺ ions (blue) are being replaced by Fe²⁺ ions (pale green). The deposited copper is spongy and reddish-brown.