Here is a list of compulsory experiment report in Form 6 :
Experiment 17
Experiment 17
Purpose : To determine the percentage of aluminium in a sample X by means of the
preparation of a complex compound of aluminium with
8 – hydroxyquinoline.
Materials : KA 1 is a solution of 8 – hydroxyquinoline in ethanoic acid.
KA 2 is 2.0 mol dm־³ aqueous ammonium ethanoate.
KA 3 is sample X.
KA 4 is 2.0 mol dm־³ hydrochloric acid.
Apparatus : Electric balance ± 0.01g (common use).
Oven (common use).
Magnetic stirrer.
One 250cm³ beaker.
One 50cm³ measuring cylinder.
One Bunsen burner.
One tripod stands and wire gauze.
One retort stand and clamp.
One thermometer 0 ºC to 100 ºC.
One crucible and lid.
One filter tuner and filter paper.
One wash bottle filled with distilled water.
Introduction : Aluminium in a certain sample can be determined quantitatively by
means of the process of formation of complex compounds, for example,
an alum complex is produced by the reaction of an alum with
8 – hydroxyquinoline.
readings are recorded in the table below.
Mass of container + KA 3 / g | 104.69 |
Mass of empty container / g | 104.43 |
Mass of KA 3 / g | 0.26 |
All of the KA 3 are placed into a 250cm³ beaker, and 150cm³ of
distilled water are added followed by one drop of KA 4 . The mixture
is warmed to a temperature between 60 ºC and 70 ºC. Then 25cm³ of
solution KA 1 are added, slowly followed by 50cm³ of solution
KA 2 . A precipitate will be formed. The beaker is removed. This
solution is stirred for half an hour by using a magnetic stirrer.
An empty crucible is weighed and the readings are recorded in the
table below. The solution above is filtered and the precipitate is
washed with cold distilled water. The precipitate is transferred into an
empty crucible and the precipitate is dried in the oven at about 120 ºC.
The crucible is cooled and weighed together with its contents.
Mass of crucible + precipitate / g | 30.43 |
Mass of empty crucible / g | 30.28 |
Mass of precipitate / g | 0.15 |
Question :
(c) Explain.
(i) Why the mixture of solutions KA 1 and KA 2 needs to be stirred for half an
hour using the magnetic stirrer?
To make the solution KA 1 and KA 2 to be uniform to get better
reaction and transmit heat uniformly.
(ii) Why the complex precipitate is washed with cold water?
To separate out the fluorine particle with the pure precipitate.
(d) How would you ensure whether the complex precipitate obtained is completely dried? First, randomly take the mass of precipitate in different time after 1 hour and then
until get the constant mass to ensure the complex precipitate obtained is
completely dried.
(e) Calculate the mass of 1 mole of complex compound with the formula Al(C9H6NO)3.
Mass = 27 + 3[9(12) + 6(1) + 14 + 16]
= 27 + 432
= 459 g
(f) Calculate the percentage of aluminium in the complex compound.
27_
Percentage of aliminium = 459 x 100 %
= 5.882 %
(g) Calculate the percentage of aluminium in sample X.
459 g of Al(C9H6NO)3 contains 27 g of Al.
0.15 g of sample X contains Y g of Al.
27 x 0.15
Y = 459
Y = 0.00882 g
0.00882
Percentage of aluminium in sample X = 0.26 x 100 %
= 3.392 %
Conclusion : The percentage of aluminium in sample X is 3.392 %.
Comment : (i) Temperature must be constant between 60 ºC and 70 ºC when
continue the reaction to prevent error occurred.
(ii) We should carry out technique – synthesis in right way, do not need
do not put too many salts into the distilled water.
2 comments:
very2 useful..tq very much
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