Leeming SHS Yr 11 Chemistry
STAWA Exp 17
Student’s Name:
Date :
Preparation and properties of oxygen - O2 (g)
Background
Oxygen gas makes up about one-fifth of the Earth’s atmosphere and is essential in
sustaining life. It also has several uses including the burning out of impurities in
steel, in hospitals to assist patients’ breathing, as an aid to combustion in oxyacetylene torches and an oxidising agent in modern rocket motors.
Equipment and chemicals
250 mL conical flask with flexible
gas delivery tube fitted into a rubber
stopper
large pneumatic trough
beehive shelf
metal tongs
deflagrating spoon
2 large test tubes with stoppers
25 mL hydrogen peroxide - H2O2 20 volume
1g manganese dioxide – MnO2
or a ball of modelling clay rolled in
MnO2
wooden splint
test tube rack
1g sulfur S8 for demonstration
Bunsen burner
steel wool – rolled into a 2cm
length, 5mm diameter for
demonstration
2 gas jars with frosted glass lids
Safety
• manganese dioxide dust should be avoided especially when pregnant.
• hydrogen peroxide in high concentrations is corrosive and an oxidising
agent.
International safety card information
hydrogen peroxide - http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc01/icsc0164.htm
manganese dioxide - http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc01/icsc0175.htm
H2O2
STAWA17.DOC
Adapted from STAWA Exp 17
H2O2
harmful - MnO2
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Leeming SHS Yr 11 Chemistry
STAWA Exp 17
Procedure
Gas production
1.
Set up the gas generating equipment to collect the oxygen by the downward
displacement of water as shown in the diagram below.
oxygen gas
gas jar
or test tube
water displaced
downwards
water in a
pneumatic trough
hydrogen peroxide
+ manganese dioxide
beehive shelf
2.
Half fill a pneumatic trough or bucket with tap water and place the beehive
shelf in the water.
3.
Fill two test tubes and two gas jars with tap water. For each test tube in turn,
place one finger over the mouth, invert, and place the unsealed end under the
water surface before removing you finger.
For the gas jars, fill with tap water then place the frosted lids on them. To
prepare for filling, hold the glass lids and invert the jars. Place the jars in the
pneumatic trough water.
4.
Place a small amount (pea-sized) of manganese dioxide into the conical flask.
Add about 20 mL of 20-volume hydrogen peroxide. Quickly replace the gas
delivery stopper.
5.
Allow a little gas to pass through the delivery tube (to flush our the air) before
collecting the gas. Collect the gas by placing the end of the delivery tube
under the opening of the test tube. The gas will force the water out. When full
of gas, place a stopper on the end of the test tube while under water. Take
the test tube out and put it in the test tube rack for later use. Fill the other test
tube in the same way.
If the reaction slows down, add more hydrogen peroxide.
6.
Fill the two gas jars in a similar manner this time holding the delivery tube
under the beehive shelf while holding the inverted gas jar in place over the
beehive shelf. Slide the glass lid over the gas jar when it is full and store it
upright until needed.
7.
When all the gas is collected you may dispose of the reaction mixture by
flushing it down the sink.
STAWA17.DOC
Adapted from STAWA Exp 17
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Leeming SHS Yr 11 Chemistry
STAWA Exp 17
Gas testing
8.
Use the first test tube of oxygen to check and record its colour and odour.
9.
Into the 2nd test tube place a glowing (not burning) wooden splint. Record your
observations.
10.
Perform in the fume cupboard - Place some sulfur powder in a deflagrating
spoon and carefully ignite it in a Bunsen flame. Note the intensity of the flame.
Quickly place the deflagrating spoon into a gas jar of oxygen and immediately
observe the intensity of the flame. Record all your observations carefully.
11.
Perform in the fume cupboard - Take a small amount of steel wool and roll it
into a 2cm long x 0.5cm diameter length. Hold the steel wool using metal
tongs and heat it in a Bunsen flame until it starts to glow. Immediately place
the steel wool in a gas jar of oxygen and replace the cover slip. Record all
your observations carefully.
12.
Clean up time.
Pour spent chemicals into waste bottles provided. Wash all glassware, wipe
the bench and make things ready for the next group.
STAWA17.DOC
Adapted from STAWA Exp 17
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Leeming SHS Yr 11 Chemistry
STAWA Exp 17
Data Sheet
O2 - Oxygen gas
observations
colour
odour
glowing splint test
combustion of sulfur in AIR
combustion of sulfur in OXYGEN
combustion of steel in AIR
combustion of steel in OXYGEN
Processing of Results
1.
Write a balanced equation for the preparation of oxygen.
2.
What is the function of the manganese dioxide [MnO2] in the preparation?
3.
List the following physical properties of oxygen –
•
colour
•
odour
•
density
•
solubility in water
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Adapted from STAWA Exp 17
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Leeming SHS Yr 11 Chemistry
4.
STAWA Exp 17
From your observations of the burning of various substances in oxygen what
can you say about the rates of these processes in pure oxygen compared with
air?
Explain this –
5.
Write an equation for the combustion of sulfur in oxygen.
6.
Write an equation for the combustion of iron in oxygen.
7.
Could oxygen be collected by the upward displacement of air?
Explain your answer.
STAWA17.DOC
Adapted from STAWA Exp 17
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