Produce oxygen by heating potassium manganate(VII), then identify it with a glowing splint
The glowing splint will reignite if enough oxygen is produced from the KMnO4 reaction, showing student the properties of this common gas.
This experiment should take 30 minutes.
- Eye protection
- Test tube holder
- Ceramic wool
- Test tube
- Bunsen burner
- Heat-proof mat
- Potassium manganate (VII)
Health, safety and technical notes
- Read our standard health and safety guidance.
- Always wear eye protection.
- When KMnO4 is heated, tiny particles shoot out. (These are trapped by the ceramic wool.)
- Potassium manganate is an oxidiser and harmful, see CLEAPSS Hazcard HC081.
- Place two spatula measures of potassium manganate(VII) in a test tube.
- Place a small piece of ceramic wool near the top of the test tube. This stops fine dust escaping.
- Gently heat the test-tube containing the potassium manganate(VII).
- Light a splint and extinguish it, to make a ‘glowing splint’.
- Place the glowing splint just above the top of the test tube. Keep heating the test tube. The splint should relight.
- Scrape out the ceramic wool. Let the test tube cool to room temperature and then wash it out.
- Notice the colours produced when the test tube is washed out.
- Record your observations.
As an extension, students could add half a spatula measure of manganese(IV) oxide (HC060) to 20 cm3 (20 volume) hydrogen peroxide (HC050) solution at room temperature and test for oxygen.
- What is the chemical formula for potassium manganate(VII)?
The preparation and properties of oxygen - student sheetPDF, Size 0.17 mb
The preparation and properties of oxygen - teacher notesPDF, Size 0.13 mb
This practical is part of our Classic chemistry experiments collection.
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