SPM Chemistry Form 4 Notes – Electrochemistry (Part 6)

by BerryBerryTeacher

in Berry Reference (Notes)

Industrial uses of electrolysis are very important to produce many raw materials and feedstock for generating electricity. However, most Berry Readers might not even realise the magnitude of the electrolysis-based industry and the economical impact if electrolysis is not used. Among example of large-scale industrial uses of electrolysis include the production of aluminium (Hall-Heroult process), lithium, sodium, potassium, calcium, chlorine and even hydrogen.

This Part 6 of Berry Berry Easy notes for SPM Form 4 Chemistry on Electrochemistry is a wrap-up of the first 6 sub-topics in electrochemistry. Here, you’ll learn how to predict the products of electrolysis of aqueous solutions and also the various categories of electrolysis in industries. Do read up on the first 5 parts before proceeding with this post.

[Tips: In essay questions, when asked for uses of electrolysis in industries, do not just throw examples. You'll need to categorise them based on the end product, name a couple of example and describe in minor detail how they differ from the other categories. When you have the time, putting in a diagram always helps too.]

SPM Chemistry Form 4 Notes – Electrochemistry (Part 6)

Voltaic Cell

Voltaic Cell

Predict the Products of Electrolysis of Aqueous Solutions

Main factor: Position of ions in the electrochemical series

  • Cation: The higher the position in the electrochemical series are very stable (remain as cation). Example: K+ and Na+ are never discharged in an aqueous solution in electrolysis.
  • Anions: The higher the position in the electrochemical series are very stable (remain as anion). Example: F - and SO42- are never discharged in an aqueous solution in electrolysis.

Second factor: Concentration of the electrolyte

Third factor: Types of electrode as anode

Electrolysis in Industries

A. Extraction of reactive metals

  • Reactive metals: Sodium, calcium, magnesium and aluminium extract from their compounds
  • Example: extraction of aluminium from aluminium oxide, Al2O3 (bauxite) by using cryolite, Na3AlF6 at 980˚C.

B. Purification of metals

  • Anode: impure metal
  • Cathode: pure metal
  • Electrolyte: solution containing the ions of the metal to be purified
  • Example: purification of impure copper metal.

C. Electroplating of metals

  • Electroplating is a process of coating the surface of metal objects with a thin and even layer of another metal.
  • Importance of electroplating is to prevent corrosion and improve the appearance.
  • Cathode: object to be electroplated
  • Anode: pure plating metal
  • Electrolyte: aqueous solution contains plating metal ions

This marks the end of this post. The next part, Part 7 of short notes from Berry Berry Easy on SPM Form 4 Chemistry – Electrochemistry will be on voltaic cell/galvanic cell and Daniell cell.

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