Half Equations
Chemistry: AQA GCSE Higher, topic 4.4.6
Half Equations
During electrolysis, different reactions take place at the different electrodes. The reactions that happen at each electrode can be shown using half equations. The electrolysis of lead bromide is an example of this:
At the anode (positive electrode)
- Oxidation reactions happen i.e. negatively charged ions lose electrons.
- 2Br- → Br2 + 2e-
At the cathode (negative electrode)
- Reduction reactions happen i.e. positively charged ions gain electrons.
- Pb2+ + 2e- → Pb
Test yourself on Half Equations
What type of reaction happens at the anode (positive electrode) during electrolysis?
What type of equations are used to describe the different reactions taking place at each electrode?
Select the correct statement for each pair.
In the half equation Pb2+ + 2e- → Pb, which species gains electrons?
In the half equation 2Br- → Br2 + 2e-, which species loses electrons?