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CIE IGCSE Chemistry
Revision Notes
IGCSE
Chemistry
CIE
Revision Notes
4. Electrochemistry
4.1 Electrolysis
4.1.1 Electrolysis Principles
4.1.1 Electrolysis Principles
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1. States of Matter
Test Yourself
2. Atoms, Element…
3. Stoichiometry
Electrolysis: General Principles
When an electric current is passed through a molten ionic
compound the compound decomposes or breaks down
4. Electrochemistry
The process also occurs for aqueous solutions of ionic compounds
Covalent compounds cannot conduct electricity hence they do not
undergo electrolysis
4.1 Electrolysis
Ionic compounds in the solid state cannot conduct electricity either
since they have no free ions that can move and carry the charge
4.1.1 Electrolysis
Principles
4.1.2 Electrolysis of
Molten Compounds
4.1.3 Electrolysis of
Aqueous Sodium
Chloride & Dilute Sulfuric
Acid
Particles in ionic compounds are in fixed position in the solid state but
can move around when molten or in solution
4.1.4 Electrolysis of
Key terms used in a simple electrolytic cell
Aqueous Solutions
Electrode is a rod of metal or graphite through which an electric
current flows into or out of an electrolyte
4.1.5 Ionic Half Equations
Electrolyte is the ionic compound in a molten or dissolved solution
that conducts the electricity
Anode is the positive electrode of an electrolysis cell
4.2 Applicatio…
Anion is a negatively charged ion which is attracted to the anode
Cathode is the negative electrode of an electrolysis cell
Cation is a positively charged ion which is attracted to the cathode
5. Chemical Energ…
6. Chemical Reacti…
7. Acids, Bases & S…
8. The Periodic Table
9. Metals
10. Chemistry of th…
11. Organic Chemis…
The basic set-up of an electrolytic cell
12. Experimental Te…
Metals and hydrogen form positively charged ions and so either a
metal or hydrogen gas is formed at the cathode
Non-metals form negatively charged ions and so non-metals
(except hydrogen) are formed at the anode
Exam Tip
Use the PANIC mnemonic to remember which electrode is the positive
and which is the negative:
Positive (is) Anode Negative Is Cathode
Electrolysis: Charge Transfer
EXTENDED
During electrolysis, current needs to flow around the circuit
In order for this to occur, charge must be transferred around the
circuit (current is a measure of the rate of flow of charge) by charge
carriers
The power supply provides the cathode with a supply of electrons,
causing it to become negatively charged
Positive ions (cations) in the electrolyte move towards the cathode
where they gain electrons
Negative ions (anions) in the electrolyte move towards the anode
where they lose electrons
The electrons move from the anode back towards the power supply
So, in a complete circuit:
Electrons are the charge carriers in the external circuit
Ions are the charge carriers in the electrolyte
Diagram showing the direction of movement of electrons and ions in
the electrolysis of NaCl
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Author: Alexandra
Alex studied Biochemistry at Newcastle University before embarking upon a career in
teaching. With nearly 10 years of teaching experience, Alex has had several roles including
Chemistry/Science Teacher, Head of Science and Examiner for AQA and Edexcel. Alex’s
passion for creating engaging content that enables students to succeed in exams drove her
to pursue a career outside of the classroom at SME.
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