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• NZQA website

Chemistry 3.3 Describe oxidation–reduction processes

Subject content

• Processes involve reactions and calculations, which may include:
  • electrochemical cells and their properties

  You should be able to:

  • define the terms electrolyte, anode, cathode, salt bridge – see electrochemistry principles
  • distinguish between the internal and external circuit
  • write ionic equations to describe the reactions occurring in electrochemical cells
  • label diagrams of electrochemical cells to show cell contents, electrode polarity, and direction of electron flow – see animation of electrochemical cells
  • write cell diagrams of described electrochemical cells
  • apply principles of electrochemistry to everyday applications of electrochemical cells.
  
  
  • use of reduction potentials

  You should be able to:

  • use E^o values to predict if a reaction will occur spontaneously – see using redox potentials
  • use E^o values to rank species with regards to oxidising or reducing strength.
  
  
  • spontaneity of oxidation–reduction reactions.

  You should be able to write balanced half equations and full equations for a range of redox reactions. Define the terms oxidation, reduction, oxidant, oxidising agent, reductant, reducing agent, and spectator ion.

• Calculations may include:
• determination of oxidation numbers
• mole ratios
• calculations related to electrochemical cells.

• Knowledge of appearance and state of the following reactants and the product to which they are converted. This means you should be able to recognise and identify the colour of a range of oxidants and reductants and any associated colour changes.
  • Oxidants will be limited to:

  O², Cl₂, I₂, Fe³⁺, dilute acid (with metals), H₂O₂, MnO₄^- (reacting in acidic, basic, or neutral conditions), Cu²⁺, Cr₂O₇^2-/H⁺, OCl^-, concentrated HNO₃, IO₃^-, MnO₂

  • Reductants will be limited to:

    metals, C, CO, H₂, Fe²⁺, Br^-, I^-, H₂S, SO₂, SO₃^2-, S₂O₃^2-, H₂O₂, H₂C₂O₄.

Visit the site Internet Chemistry – Oxidation/reduction for information, interactive exercises, and applications of oxidation-reduction reactions.

Check out this animated online resource: The Drive to Make Things Happen: Redox Reactions and Electrochemical Potential. You will require the plug-ins Shockwave and Chime, to view the animations and 3D molecules.

Test your knowledge about redox reactions on Auckland University's site Bestchoice For Chemistry. Select Course 13, Option Redox. This is a free site, but note that there is a requirement that you login.

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