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OCR A-Level Chemistry Pag 12.1 Investigating Iron Tablets
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- Organic Chemistry
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26/04/2022PAG 12.1 - Investigating Iron Tablets
INTRODUCTION
Iron tablets (also known as ferrous fumarate) are commonly prescribed as a medication to treat and
prevent iron deficiency (anaemia).1 They may also be taken by people who have any other conditions
affecting their iron levels, red blood cells or bowels.1
Iron is used in medicines to aid the body in making red blood cells and replace naturally sourced iron
in the body (made by consuming iron rich foods). Red blood cells contain haemoglobin, each
haemoglobin molecule has a haem group containing iron which binds to oxygen and forms
oxyhaemoglobin.2 This allows oxygen to be transported around the body, people with iron deficiency
may experience symptoms due to the lack of oxygen that is in the body and counteract this by taking
iron tablets.
Iron tablets come in two strengths containing either 210mg or 322mg of iron in each tablet.1 The
active ingredient in these tablets is Iron(II) fumarate but also contain other ingredients such as: maize
starch, sodium lauryl sulphate, gelatin, liquid paraffin and purified water.3 Iron tablets contain roughly
65-70mg of iron in a standard tablet.3
The common daily intake of iron tablets for adults and children over the age of 12 is: 210mg tablets (2
or 3 times a day), 322mg tablets (1 or 2 times a day).1 Children under 12 should be instructed on the
recommended daily intake from their doctor based on the child's age or weight.1
A redox titration must be completed to find the concentration of Fe 2+ ions in a solution. This can be
done by adding a standard solution of potassium manganate(VII) to a burette.4 Five iron tablets should
be mixed with an excess of dilute sulfuric acid to form a 250cm3 solution in a volumetric flask.4 This
will provide H+(aq) ions that allow for the reduction of MnO4– (aq) ions.4 The potassium manganate
(VII) will be run from a burette into the iron tablet solution.4 As the potassium manganate (VII) reacts,
the solution will turn colourless.4 The end-point of the titration can be seen by observing a permanent
pink colour which indicates that there is an excess of MnO4– (aq) ions present.4 This titration should be
repeated until concordant results within 0.10 cm3 of each other are obtained.4 The average of two
concordant titres will give the mean volume of potassium manganate (VII). This will be used to find
the moles MnO4– (aq) ion being used to oxidise the Fe2+ ions. The moles of Fe2+ ions can be calculated
to work out the concentration of Fe2+ in the iron tablet.
Potassium manganate (VII), KMnO4 is reduced from deep purple manganate (VII) ions to pale pink
manganese(II) ions because it is a self-indicating reagent. This is why it can be used to monitor the
progress of the reaction since a chemical indicator is not required to detect the end point.
The half equations involved in this reaction:
MnO4– (aq) + 8H+(aq) + 5e– ⟶ Mn2+(aq) + 4H2O(l)
5Fe2+(aq) ⟶ 5Fe3+(aq) + 5e-
Overall equation:
MnO4–(aq) + 8H+(aq) + 5Fe2+(aq) ⟶ Mn2+(aq) + 5Fe3+(aq) + 4H2O(l)
References:
1
NHS, 2019, Accessed 26/04/2022 <https://www.nhs.uk/medicines/ferrous-fumarate/>
2
Parsons R, Fielding D, Park A, Rachael R, Camila S, 2018, A-level Biology Exam Board: OCR A
Complete Revision & Practice, Page 89, first edition, CGP, Accessed 26/04/2022
3
Datapharm, 2020, Accessed 26/04/2022 <https://www.medicines.org.uk/emc/files/pil.2821.pdf>
4
Ritchie R, Gent D. 2015, A Level Chemistry for OCR A, first edition, page 376-377, OCR, Accessed
26/04/2022
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