Laboratory Preparation of
Oxygen
Using Hydrogen Peroxide
Chemistry - Form 2
By: B.E.Namithambo, Bed.Sc-Chemistry,
Chemistry examiner.
Pre-Lab Notes
• Oxygen is prepared in the laboratory by catalytic
decomposition of hydrogen peroxide(H₂O₂)
• Catalytic decomposition means breaking down of a
compound using a catalyst.
• In this case, hydrogen peroxide is split into water and
oxygen gas.
• Manganese dioxide(MnO₂) is used as a catalyst
• The oxygen gas is collected by letting it push water out of
a gas jar.
• This is called collection over water or downward
displacement of water
•This is because oxygen is slightly soluble in water..
Chemical Reaction
Word Equation:
• Hydrogen Peroxide → Water + Oxygen
Chemical Equation:
Materials Needed
• Hydrogen peroxide (H₂O₂)
• Manganese dioxide (MnO₂)
• Round-bottomed flask
• Delivery tube
• Water trough or basin
• Bee hive shelf
• Gas jar
Experimental set up
Diagram taken from:
https://www.esomake.co.ke/
Procedure
1. Fill a basin halfway with water.
2. Place a bee hive shelf inside the basin.
3. Fill a gas jar completely with water and
carefully invert it over the bee hive shelf
(underwater) so that no air enters. The jar
should now be upside down and full of water.
4. Put a small amount of manganese dioxide
(MnO₂) into a round-bottomed flask. This will
act as a catalyst.
5. Fix a dropping funnel into the flask using a
rubber stopper.
Procedure cont…
6. Pour hydrogen peroxide (H₂O₂) into the dropping funnel
carefully.
7. Connect a delivery tube from the flask to underneath the
inverted gas jar in the basin (through the bee hive shelf).
8. Slowly open the tap of the dropping funnel to allow hydrogen
peroxide to drip onto the manganese dioxide in the flask
9. Observe and record if there will be fizzing/effervescence
inside the flask. This shows that a gas is being produced.
10. Watch bubbles of oxygen gas pass through the delivery
tube and fill the gas jar by pushing the water out.
11. Once the gas jar is full, remove the delivery tube before
stopping the reaction to prevent water from sucking back into
the flask.
What You Will See
• Bubbles form quickly.
• Gas has no colour or smell.
• Water level in gas jar goes down as gas fills it.