Extracting Copper (Oxford AQA IGCSE Combined Science Double Award): Revision Note

How is Copper Obtained?

How is copper purified? 

• The electrolysis of aqueous CuSO₄ using graphite rods produces oxygen and copper

• By changing the electrodes from graphite to pure and impure copper, the products can be changed at each electrode

• Electrolysis can be used to purify metals by separating them from their impurities

• In the set-up, the impure metal is always the anode, in this case the impure copper

• The cathode is a thin sheet of pure copper

• The electrolyte used is an aqueous solution of a soluble salt of the pure metal at the anode, e.g. CuSO₄

• Copper atoms at the anode lose electrons and go into solution as ions:

Cu ⟶ Cu²⁺  +  2e^–

• The anode thus becomes thinner due to loss of atoms and the impurities fall to the bottom of the cell as sludge

• The copper(II) ions are attracted to the cathode where they gain electrons and form now purified copper atoms

• The cathode gradually becomes thicker

Cu²⁺  +  2e^– ⟶ Cu

• The anode sludge is a highly valuable material and is further refined as it often contains small quantities of precious metals like silver which are found as impurities in the unrefined copper

Purification of copper 

Obtaining Copper by Displacement

• Copper can also be extracted using displacement

• To save scrap iron from going into landfill, it can be used to displace copper from solution

  • E.g. copper sulfate, copper nitrate

• Iron is more reactive than copper so can displace copper from solution

iron + copper sulphate → copper + iron sulphate

Fe (s) + CuSO₄ (aq) → FeSO₄ (aq) + Cu (s)

• We can break this down into an ionic equation

Fe (s) + Cu²⁺ (aq) + SO₄^2– (aq) → Fe²⁺ (aq) + SO₄^2– (aq) + Cu (s)

Fe (aq) + Cu²⁺ (aq) → Fe²⁺ (aq) + Cu (s)

• The Fe atom has lost electrons to become a Fe²⁺ ion, it has been oxidised

• The Cu²⁺ ion has gained electrons to become a Cu atom, it has been reduced