Oxidation & Reduction (OCR GCSE Combined Science A (Gateway)): Revision Note
Oxidation & Reduction
Oxidation and reduction involve the addition or removal of oxygen from a substance
Oxidation is a reaction in which:
Oxygen is added to an element or a compound
Reduction is a reaction in which:
Oxygen is removed from an element or a compound
A redox reaction is one where oxidation and reduction are both taking place at the same time
In the following reaction:
ZnO + C ⟶ Zn + CO
The carbon atom has been oxidised since it has gained oxygen
The zinc oxide has been reduced since it has lost oxygen
This is an example of a redox reaction as oxidation and reduction are both taking place
Carbon is known as a reducing agent as it has reduced another substance (the zinc oxide)
Zinc oxide is known as an oxidising agent as it has oxidised another substance (the carbon)
Worked Example
Magnesium reacts with zinc oxide:
Magnesium + zinc oxide → magnesium oxide + zinc
Explain which substance is reduced and which substance acts as a reducing agent
Answer:
Zinc oxide is reduced because it loses oxygen
Magnesium acts as the reducing agent as it reduces the zinc oxide
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