Transcript Document 7346098

How much iron is in an iron tablet?
Group members: Choi Chuen Ching (5)
Fong Ka Yee (6)
Leung Chi Lai (12)
Lui Lai Sin (16)
Aim
1. To investigate how much iron is in iron
tablets.
2. To compare the percentage of iron in
iron tablets from two different
manufacturer.
3. To find out which one is worth buying.
Why iron is essential to our body?
~the formation of haemoglobin.
If we do not have enough iron in our diet, what will
happen?
The deficiency of iron : anaemia
What can be done if we suffer from anaemia?
~ consult doctor
~need to take iron tablet under the guidance of doctor.
How can we prevent anaemia?
obtain iron from :
~Liver
~eggs
~beef
~green leafy vegetables, etc.
Daily requirement of iron:
Male : 10mg
Female : 18mg
Principles
A. Standardization of Potassium Permanganate Solution
Potassium permanganate (KMnO4)
~slowly decomposes in sunlight
~readily oxidizes organic matter.
∴stored in brown bottle and has to be standardized before use.
Reagents for the standardization of KMnO4 :
~oxalic acid
~sodium oxalates
~ammonium iron(II) sulphate
~arenious oxide.
KMnO4 does not require a chemical indicator for the detection of
end point . Because :
KMnO4 is deep purple in color and is reduced to almost colorless
solution (Mn2+ salts are light pink in color).
In this experiment :
Primary standard to standardize the KMnO4 solution :
~ Solid ammonium iron(II) sulphate (AIS)
~> stable at room temperature
~> can be obtained in pure state
∴ It can be used as a primary standard in redox titration.
However,
A neutral solution of AIS is unstable and iron will precipitate out
as the hydroxide. Therefore it should be dissolved in an acidified
solution, preferably oxygen free.
In this experiment, a standard ammonium iron(II) sulphate
solution is used to standardize the potassium permanganate
solution. The overall equation for the reaction is:
MnO4- + 5Fe2+ + 8H+
Mn2 + 5Fe3+ + 4H2O
B. Determination of the mass of iron in one gram of the iron tablet
The iron in iron tablets comes from hydrated iron(II) sulphate
(FeSO4．7H2O) (sometimes called hydrated ferrous sulphate).
As its name suggests, iron(II) sulphate contains Fe2+ ions. These
react with the MnO4- ions in the potassium permanganate as shown
in the equation below:
5Fe2+ + MnO4 + 8H+
5Fe3+ + Mn2+ + 4H2O
The colour of the potassium permanganate disappears as it reacts
with the Fe2+ ions. This provides a way of deciding when the
titration is complete because, when all the Fe2+ ions are gone, just
one drop extra of potassium permanganate solution will make the
titration mixture turn pale purple.
Procedures
A. Standardization of potassium manganate(VII) solution
1) About 9.8g of ammonium iron(II) sulphate was accurately
weighed out. Then it was dissolved in 25ml of sulphuric acid.
The mixture was diluted with distilled water and was made up
to exactly 250.0ml of solution.
2) 25.0ml of this solution was pipetted into a conical flask. 25ml
of 1M sulphuric acid was added to it.
3) It was titrated with potassium manganate(VII) solution until a
permanent pink colour was obtained (would not disappear after
30 seconds).
4) The molaruty of the manganate(VII) solution was calculated.
B. Determination of the mass of iron in one gram of the iron tablet
1) Five iron tablets were weighed accurately and their masses were
recorded. .
2) They were grinded up in a mortar and were pestled with about 5
cm3 of 1M sulphuric acid.
3) The acid and tablets were transferred through a small filter
funnel into a 250.0 cm3 volumetric flask. The mortar and
pestle were rinsed with further quantities of acid, each portion
were transferred carefully into the flask, until all trace of the
iron tablets had gone.
4) The funnel was rinsed with
more acid, and then 1M sulphuric
acid was added to the flask until the
solution reaches the 250.0 cm3
mark. The flask was stoppered and
was inverted several times to mix
the solution.
5) 25.0 cm3 of the solution was pipetted from the volumetric
flask and was transferred to a conical flask.
6) A burette was filled with the potassium manganate(VII)
solution.
7) The potassium manganate(VII) solution was titrated
against the solution in the conical flask. The volume of
potassium manganate(VII) solution used at the end point
was recorded.
8) The above steps were repeated but using different brands
of iron tablets in step (1).
Result
Standardization of potassium permanganate solution
Trial
1
2
3
Initial/ml
0.10
0.10
0.20
0.00
Final/ml
24.90
25.00
25.00
24.70
Vol.
Used/ml
24.80
24.90
24.80
24.70
Average volume used = 24.80ml
Enteric-coated 167mg iron tablets
Weight of 5 tablets = 1.067g
Trial
1
2
3
Initial/ml
0.00
3.00
5.70
8.40
Final/ml
3.00
5.70
8.40
11.20
Vol.
Used/ml
3.00
2.70
2.70
2.80
Average volume used = 2.73ml
Enteric-coated 300mg iron tablets
Weight of 5 tablets = 1.580g
Trial
1
2
3
Initial/ml
0.95
6.45
17.50
22.85
Final/ml
6.45
11.85
22.85
28.25
Vol.
Used/ml
5.50
5.40
5.45
5.40
Average volume used = 5.42ml
After calculation, we found that there is 142.76mg of
iron present in the “167mg tablet” and 191.42mg of iron
present in the “300mg tablet”.
Then we decided to remove the coating of the tablet and
see whether the coating will affect the iron content.
How about the iron tablets without
enteric-coating?
167mg iron tablets after removing the enteric-coat
Weight of 5 tablets = 0.959g
Trial
1
2
3
Initial/ml
0.00
2.55
4.90
7.25
Final/ml
2.55
4.90
7.25
9.65
Vol.
Used/ml
2.55
2.35
2.35
2.40
Average volume used = 2.37ml
300mg iron tablets after removing the enteric-coat
Weight of 5 tablets = 1.312g
Trial
1
2
3
Initial/ml
36.20
40.70
45.00
39.10
Final/ml
40.60
45.00
49.30
43.40
Vol.
Used/ml
4.40
4.30
4.30
4.30
Average volume used = 4.30ml
After calculation, we found that there is 138.48mg of iron
present in the “167mg tablet” and 182.88mg of iron
present in the “300mg tablet”.
Discussion
Manufacturer of the iron tablets:
“167mg tablet” --- Christo Pharmaceutical LTD HK
“300mg tablet” --- Apotec Inc.
The table showing the mass of iron present in an iron tablet
Manufacturer
Mass
Tablets with
enteric-coating
Tablets without
enteric-coating
Christo
Apotec
“167mg tablet”
“300mg tablet”
142.76mg
191.42mg
138.48mg
182.88mg
It is found that the difference between the experimental value
and the described value of the Christo is smaller than that of
Apotec.
The table showing the % of iron present in an iron tablet
Manufacturer
% of iron
Tablets with
enteric-coating
Tablets without
enteric-coating
Christo
Apotec
“167mg tablet”
“300mg tablet”
14.3%
19.1%
13.9%
18.3%
Source of error:
~The iron tablets are not completely dissolved in
sulphuric acid.
~The percentage of iron in enteric-coating may not be the
same as that of the inner part of the tablets.
~Potassium permanganate may decompose so that the
volume of KMnO4 added may not accurate enough.
~The colour of the coating may affect the observation of
end point during titration.
Observations:
We found that the “300mg tablet” is more difficult to
dissolved in sulphuric acid.
Improvement:
~Potassium permanganate solution should be used
immediately after pouring out of the brown bottle.
Conclusion
We found that the difference between the experimental
value and the described value of “167mg tablet” was
smaller than that of “300mg tablet”.
Therefore the manufacturer of “167mg tablet”
(i.e.Christo Pharmaceutical LTD HK)is more reliable
than that of “300mg tablet” (i.e. Apotec Inc.).
On the other hand, the price of both kinds of tablets
were the same. So “300mg tablet” is more worth
buying than “167mg tablet”.
The End