Chapter 16 · Oxidation and Reduction
16.7Electrolysis: Using Electricity to Do Chemistry
9 min · two checks
Predict
What is the difference between a galvanic cell and an electrolytic cell?
The idea
- Describe electrolysis as forced redox.
- Give one industrial or everyday example.
Some redox reactions will not run on their own. Electrolysis drives them by attaching a power supply that pulls electrons out of one electrode and pushes them into the other. Oxidation still happens at the anode and reduction at the cathode; the labels of the electrodes follow the chemistry, not the spontaneity. Water can be split into hydrogen and oxygen this way. Aluminum metal is produced by electrolyzing molten aluminum compounds. Recharging a phone battery is electrolysis of the cell’s own reaction.
The amount of product follows stoichiometry once you know the moles of electrons. Current × time gives charge, and charge divided by the charge of one mole of electrons gives moles of electrons. A first course often stops at the direction and the identity of the products. The essential warning: electrolytic cells consume electrical energy. They are not batteries while they are being driven.
Keep these
- Electrolysis drives nonspontaneous redox with an external voltage.
- Anode is still oxidation. Cathode is still reduction.
- Recharging a battery and producing aluminum are electrolysis.