Starter quiz
- Which electrode is positively charged in an electrolysis cell?
- anode ✓
- cathode
- electrolyte
- circuit
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- What is the role of the anode in an electrolysis cell?
- to attract negative ions ✓
- to attract positive ions
- to conduct electricity
- to gain electrons
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- What happens to negative ions during electrolysis?
- They gain electrons at the anode
- They lose electrons at the anode ✓
- They gain electrons at the cathode
- They remain in the electrolyte
-
- What happens to positive ions during electrolysis?
- They gain electrons at the cathode. ✓
- They lose electrons at the anode.
- They remain in the solution.
- They are converted to gas.
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- What is produced at the cathode during the electrolysis of copper sulfate solution using copper electrodes?
- copper ions
- oxygen gas
- pure copper ✓
- water
-
- Why must the electrolyte contain the same ions as the metal being purified?
- to increase the conductivity
- to ensure effective transfer of metal ions ✓
- to prevent the formation of gases
- to keep the electrolyte balanced
-
Exit quiz
- What is the main purpose of using electrolysis in copper purification?
- to dissolve impurities
- to produce oxygen gas
- to deposit pure copper at the cathode ✓
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- What happens to the mass of the anode during copper purification by electrolysis?
- It decreases as copper ions move into the electrolyte. ✓
- It increases as copper ions are deposited.
- It remains the same.
-
- What is a common application of electrolysis besides purification?
- crystallisation
- electroplating ✓
- filtration
-
- What happens to impurities in the anode during copper purification?
- They deposit on the cathode.
- They dissolve in the electrolyte.
- They form a residue in the electrolyte solution. ✓
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- To electroplate a bracelet using silver, the anode is...
- the bracelet.
- the electrolyte.
- the silver electrode. ✓
-
- Which of the following are benefits of electroplating?
- increased solubility of the material
- decreased electrical conductivity
- improved appearance and durability of the surface ✓
- lower production cost of the material
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Worksheet
Presentation
Video
Lesson Details
Key learning points
- Purification of copper involves using copper electrodes in an electrolyte.
- The electrolyte must contain the same ions, in solution, as the metal being purified by electrolysis.
- Measuring the mass change in the copper electrodes demonstrates the transfer of copper.
- Impurities in the anode do not transfer to the cathode, leading to pure copper deposition.
- Other uses for this technique include electroplating, where you would use multiple metals e.g. gold.
Common misconception
Pupils do not always appreciate the difference between using inert carbon electrodes and metal electrodes, which will take part in the reaction.
Provide pupils with the opportunity to investigate the electrolysis of copper sulfate with both inert electrodes and with copper electrodes and then compare the results.
Keywords
Pure - a single element or compound that is not mixed with any other substance
Anode - a positively charged electrode, in an electrolysis cell, to which the anions are attracted
Cathode - a negatively charged electrode, in an electrolysis cell, to which the cations are attracted
Electrolyte - a liquid or an aqueous salt solution that contains freely moving ions
Electroplating - a process that uses electricity to deposit a thin layer of metal onto the surface of another conductive object