​Syllabus dot points

• 3.2 d: ​apply the definitions of oxidation and reduction in terms of electron transfer and oxidation numbers to a range of reduction and oxidation (redox) reactions

​What we will cover

• ​oxidation and reduction

• redox reactions

​General Definition

• ​a reaction where one or more electrons are transferred from one atom to another

• oxidation = loss of electrons

• reduction = gain of electrons

• occur simultaneously, because the electrons must go somewhere. Therefore RedOx reaction

​Example:

​When magnesium metal reacts with oxygen gas and form solid magnesium oxide

• ​magnesium loses two electrons ​to become Mg²⁺ - so it is oxidised

• oxygen gains two electrons to become O^2- - so it is reduced

• ​therefore, a redox reaction

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​Half equations

• ​Singles out the oxidation and reduction within the overall reaction

• can be combined to form the overall net ionic equation

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Sometimes you have to balance the number of electrons

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​What would the balanced net ionic equation be for the half equations, knowing you have to balance the amount of electrons:

​Multiply the entire oxidation reaction by 3

Multiply the entire reduction reaction by 2 ​

​Oxidising and Reducing Agents

• oxidising agent = substance that makes oxidation occur in another substance (or the substance that gets reduced)

• reducing agent = substance that makes reduction occur in another substance (or the substance that gets oxidised)

• Example:

  • copper is reduced, and zinc is oxidised

  • therefore, copper is the oxidising agent, and zinc is the reducing agent ​

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​Up next:

• ​Oxidation numbers

• ​Galvanic cells