Electrolysis
Electricity drives a non-spontaneous reaction.
About this topic
Electrolysis uses electrical energy to drive a non-spontaneous chemical reaction. In an electrolytic cell, the anode is positive (oxidation) and the cathode is negative (reduction), the opposite of a galvanic cell. The electrolyte must be molten or dissolved so ions can move. Molten sodium chloride gives sodium at the cathode and chlorine at the anode.
Positive ions migrate to the cathode and gain electrons; negative ions go to the anode and lose them. In aqueous solutions, water can compete: at the cathode, less reactive metals are deposited while reactive ones like sodium give hydrogen instead, and at the anode, halide ions give halogens while sulfate or nitrate give oxygen from water. The amount of substance produced is proportional to charge passed (Faraday's laws), with charge Q = current x time.
Worked example: passing 2.0 A for 965 s delivers 1930 C, which is 0.020 mol of electrons, depositing 0.010 mol of copper (0.64 g) from Cu2+. Applications include extracting aluminium from molten aluminium oxide, producing chlorine and sodium hydroxide from brine, purifying copper, electroplating jewellery and cutlery with silver or chromium, and splitting water into hydrogen for fuel.
A common mistake is mixing up electrodes; remember that oxidation always occurs at the anode in both cell types. Electrolysis needs a power source, while galvanic cells make one.
Key ideas
- Used to plate metals
- Splits water and brines
- Aluminium is made by electrolysis
Quick check
Use cases: where Electrolysis helps
- Homework: review the key idea behind Electrolysis before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Electrolysis without notes.
- Visual learning: play with the interactive lab to see how Electrolysis changes when you adjust its inputs.
- Teaching a friend: explain Electrolysis in your own words, then compare your version with the key ideas.
Chemistry explains medicine, food, cleaning products, fuels and building materials.
Frequently asked questions
What is Electrolysis?
Electricity drives a non-spontaneous reaction.
What will I learn in Electrolysis?
Used to plate metals. Splits water and brines. Aluminium is made by electrolysis.
Is Electrolysis part of Chemistry?
Yes. It is one of 150 Chemistry topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Electrolysis lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Electrolysis?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.