Example 2 - Electrorefining of copper

Instead of using inert electrodes, chemists tried placing pure copper electrodes in copper sulphate solution.

The test tube from the negative electrode has a lit splint inserted, there should be a loud pop which means hydrogen is present

They found that the copper on the cathode became bigger and the copper on the anode became smaller.

Once charge was surging into the solution they found the cathode became bigger and anode became smaller

So the chemists then tried putting impure copper at the anode (copper from smelting).

NOTE: Pure copper is a better electrical conductor than impure copper. The chemists could make a lot of money if they could gather pure copper. Copper can be extracted from its ore using a smelting furnace, where copper is displaced by carbon (see reactivity series), but it is not pure – it has some impurities in it.

Impure copper from smelting processes were then inserted into the solution as an anode electrode and the the cathode was pure copper.

The chemists got pure copper.

When the charge was turned on the anode started to crumble and the pure copper cathode got bigger, pure copper was created

Wow, did the chemists get rich!