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Investigate the electrolysis of a solution
Background Information and Keywords
Background Information and Keywords
Keywords
Keywords
- Electrolysis - The process of breaking down an ionic compound using electricity
- Cation - A positively charged ion (e.g. Na+)
- Anion - A negatively charged ion (e.g. Cl-)
- Solution - When a substance has been dissolved in a solvent
- Molten - When a substance has been heated to make a liquid
- Electrolyte - A freely moving ion (found either in solution or molten)
- Electrode - An inert rod, usually made of graphite, which conducts electricity
- Cathode - The negatively charged electrode
- Anode - The positively charged electrode
- Inert - doesn't react with other chemicals (e.g. graphite)
Background Information
Background Information
"What is electrolysis, and why is it so hard?!"
Electrolysis is usually an area of chemistry a lot of people struggle with, but actually the concept actually isn't very hard.
All ionic compounds are made of a positive ion (the cation) and a negative ion (the ion). They are held together in their solid form by strong electrostatic forces of attraction between the opposite charges
The point of electrolysis is to separate the positive and negative ions, usually so we can turn all the positive metal ions into metal for us to use (e.g iron for construction or aluminium for coke cans).
Electrolysis can only be done when the ions can move freely, either when the ionic compound has been melted (molten) or dissolved in water (solution)
Once the ions in the compound are free to move, we need to separate them. The easiest way to do this is using their charges. I.e. one ion is positive and the other is negative.
An electrical field is applied to the solution using two electrodes called the anode (the positive electrode) and the cathode (the negative electrode). Because opposites attract, when the electrical field is applied all the positive ions will be attracted to the negative electrode, and all the negative ions will be attracted to the positive electrode.
Other things you need to be able to do
Other things you need to be able to do
To do the practical
To do the practical
Know what a solution, solute and solvent are
Know how to set up an electrical circuit from a diagram
Know why a solid ionic compound doesn't conduct electricity but a solution or molten one can
Know the gas tests for hydrogen, oxygen and chlorine gas
To predict the products of electrolysis
To predict the products of electrolysis
Know what a cation, anion, cathode and anode are
Know your reactivity series of metals (especially where Hydrogen is)
Know that opposite charges attract each other
Know whether an ion wants to lose or gain electrons to become an atom
To write half-equations (Higher Only)
To write half-equations (Higher Only)
Know how to balance an equation
Know whether an ion wants to gain or lose electrons to become an atom
Know what the state symbols (s), (l), (g), and (aq) mean
"How To Do It" Video
"How To Do It" Video
Watch this video to remind yourself how this practical is carried out.
What are the key steps to this practical?
What are the pieces of equipment called?
This video also explains how to write half equations (Important to know if you're doing Higher Tier!)
Diagrams
Diagrams
This is the most common set up for the practical. It's simple if we just want to make the two products from the ionic compound.
This set up might be used instead, if we want to collect and test which gasses are given off at each electrode.
Key Questions from this Practical
Key Questions from this Practical
- What factors would effect the speed of electrolysis of a solution?
- What are the two electrodes called in electrolysis?
- Why are the electrodes made of graphite?
- What types of ions are always attracted to the positive electrode?
- What types of ions are always attracted to the negative electrode?
Question Practice and Exam Questions
Question Practice and Exam Questions
Required Practicals Mastery Booklet - PAG 3 - Electrolysis.pdfPAG 3: Mastery Question Booklet
PAG 3: Mastery Question Booklet
This Mastery Booklet is filled with questions and exam questions to help you master this core practical. All answers and mark schemes are attached at the end.
Oxford Revise Revision Guide
Oxford Revise Revision Guide
GCSE Chemistry Higher (Triple) - Pages 98-101 (Information) & 102-109 (Exam Questions)
AQA GCSE Chemistry Textbook (3rd Edition)
AQA GCSE Chemistry Textbook (3rd Edition)
Pages 102-109 (Information) & 110-111 (Exam Question Practice)
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