The electrolysis of copper sulphate
There are numbers of examples of electrolysis. The electrolysis of copper sulphate is just one.
Activity :: Demonstration :
The electrolysis of copper sulphate Two copper electrodes are placed in a solution of blue copper sulphate and are connected to a source of electrical current as shown in the diagram below. The current is turned on and the reaction is left for a period of time.
- The initial blue colour of the solution remains unchanged.
- It appears that copper has been deposited on one of the electrodes but dissolved from the other.
- At the negative cathode, positively charged Cu2+ ions are attracted to the negatively charged electrode. These ions gain electrons and are reduced to form copper metal, which is deposited on the electrode. The half-reaction that takes place is as follows:
Cu2+(aq) + 2e− → Cu(s) (reduction half reaction)
- At the positive anode, copper metal is oxidised to form Cu2+ ions. This is why it appears that some of the copper has dissolved from the electrode. The half-reaction that takes place is as follows:
Cu(s) → Cu2+(aq) + 2e− (oxidation half reaction)
- The amount of copper that is deposited at one electrode is approximately the same as the amount of copper that is dissolved from the other. The number of Cu2+ ions in the solution therefore remains almost the same and the blue colour of the solution is unchanged.
In this demonstration, an electric current was used to split CuSO4 into its component ions, Cu2+ and SO2− 4.
This process is called electrolysis.