ICT
Design
DC
DPP
CE
MS
GRADE 11- CHMISTRY
INVESTIGATION investigating the properties of Period 3 oxides
Aim
The purpose of this experiment is to examine the oxides of Period 3 elements and describe
their bonding and structure.
Introduction
You carry out an investigation along similar lines to the work you did on the chlorides of the
elements in Period 3 (Experiment 4.12). However, you will not be asked to test the oxides with
cyclohexane because unlike the covalent chlorides, most of the oxides are not composed of
discrete molecules. Therefore they are unlikely to dissolve in cyclohexane and simple
experiments cannot distinguish between insolubility and slight solubility.
Requirements
safety spectacles
access to a fume cupboard
6 test-tubes
test-tube rack
1 measuring cylinder, 10 cm3
1 measuring cylinder, 100 cm3
distilled water
thermometer, 0-100 °C
1 spatula
universal indicator solution and colour chart
teat pipette
pH paper
splints
sodium peroxide, Na2O2
magnesium oxide, MgO
aluminium oxide, Al2O3
phosphorus(V) oxide, P4O10
silicon(lV) oxide, SiO2
access to sulphur dioxide cylinder or generator, SO2
Drechsel bottle
glass tubing with right-angled bend
rubber tubing for connections
HAZARD WARNING
Phosphorus(V) oxide is corrosive and irritates eyes, skin and lungs. Sodium
peroxide is also corrosive and a powerful oxidant. Sulphur dioxide is a toxic
gas with a choking smell. Therefore you must:
 do the experiment at the turn® cupboard
 wear safety spectacles
 avoid contact with skin.
1
Procedure Appearance: Part A
1. Examine the oxide samples provided and make observation on physical properties. Record
qualitative data
Procedure Appearance: Part B on mixing with water
2. Setup six test-tubes, side by side.
3. Into each test-tube pour about 5 cm3 of distilled water.
4.
In the first test-tube place a thermometer.
a Note the temperature.
b Add half a spatula-tip of sodium chloride and very carefully stir with the thermometer.
c Note, after about one minute, i) the temperature, ii) whether the solid has
dissolved and iii) anything else you see. For example, is gas evolved at any
time? If so, is the gas acidic? Can you identify it using a simple test?
d Add 2-4 drops of universal indicator solution, or use a piece of pH
paper, compare the colour with the chart provided, and note the pH
indicated.
5. . Repeat (but with more care!) the above steps 4a-d using, in turn, magnesium oxide, aluminium
oxide, silicon ( IV) oxide phosphorus (V) oxide.
6. Measure the pH of the water in the seventh test-tube by adding 2-4 drops of universal indicator
solution or by using pH paper, for comparison with the above.
7. . Bubble sulphur dioxide slowly through the water in the sixth test-tube until there is no further
change in the colour of the indicator. Note the final pH of the solution.
(You will probably be
given sulphur dioxide in liquid form in a cylinder. To obtain the gas you carefully open the valve
and the sudden decrease in pressure inside the cylinder causes the surface liquid to vaporise.
Make sure there is a Drechsel bottle between the cylinder and the water in case of suck-back.
Alternatively, your teacher may suggest other ways of generating the gas.)
8. To test the solubility of sulphur dioxide lower the delivery tube from your generator to the bottom
of the 100 cm3 measuring cylinder filled with water. Pass a slow steady stream of gas through
the water and when the air has been expelled from your apparatus look for a change in the size
of the sulphur dioxide gas bubbles as they rise up through the water.
2
Results Table 1
Na2O2A MgO
AI2O3
SiO2
P4O10
SO2
Appearance
On mixing with water
Initial temperature
Final temperature
Does it dissolve?
pH of solution
Other observation(s) (if any)
Question
1. Use your experimental results, your data book and your textbook(s) if necessary to complete a larger
copy of Table 2 below
Formula of oxide
NazOz*
MgO
A4C>3
SiOz
P40,o*
SOa*
ClaO*
Melting point/°C
Boiling point/°C
State at s.t.p.
Action of water
pH of aq. solution
Acid-base nature
Conductivity of liquid
Solubility in cyclohexane
Structure
Bonding
Table 2
2. Write equations for any reactions which took place when you added the oxides to water.
3. Comment on the change in structure and bonding in the oxides between sodium and chlorine.
4. How does the acid-base nature of the oxides of the elements in Period 3 change with increasing
atomic number?
5. Can you relate this change to the change in structure and bonding that takes place along the
period?
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