Identifying Redox Reactions by Colour Changes
Chemistry: Cambridge International GCSE Supplement, topic 6.4.5
Identifying Redox Reactions by Colour Changes
Redox reactions involve simultaneous electron loss (oxidation) and gain (reduction). Colour changes often identify these electron transfers.
What is a redox reaction?
- A redox reaction changes the oxidation states of substances.
- Oxidation means losing electrons.
- Reduction means gaining electrons.
- Redox reactions involve both at the same time.
Oxidising agent defined
- An oxidising agent takes electrons from another substance.
- It causes another substance to oxidise.
- It gains electrons itself and is reduced.
- Example: Potassium permanganate (purple) changes colour when it reduces.
Reducing agent defined
- A reducing agent gives electrons to another substance.
- It causes another substance to reduce.
- It loses electrons itself and is oxidised.
- Example: Iron filings (grey) can change colour when they oxidise.
Identifying agents by colour changes
- Look for colour changes to spot oxidising agents reducing, and reducing agents oxidising.
- Potassium permanganate changes from purple to colourless in acid.
- Copper oxide changes from black to brown when reduced to copper.
- Colour changes show electron transfer in redox reactions.
Test yourself on Identifying Redox Reactions by Colour Changes
What is the primary role of an oxidising agent in a redox reaction?
What are the colour changes to identify redox reactions and the agents involved?