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Impact of Humidity on Percentage of Iron in Ferrous Sulfate (FeSO4) Tablets
[Research Question]
What is the effect of exposure time to humidity (0hrs, 24hr, 48hrs, 72hrs, 96hrs) on the percentage (%) of
iron (Fe2+) that is present in ferrous sulfate (FeSO4) tablets (65mg), using a redox titration with potassium
permanganate (KMnO4)?
[Personal Engagement / Introduction]
I have always been intrigued and fascinated by the field of chemistry, especially its practical
implementations in the pharmaceutical industry. Having an iron deficient and anemic sibling, iron
supplements, which treat iron-deficiency anemia, have been at the forefront of my childhood. My
personal connection to iron supplements sparked my interest in performing an experiment regarding them.
Furthermore, the study of medicine and pharmaceutical drugs align with my interests that I hope to further
pursue in college. This study provides valuable experience and aligns with various career options I am
considering. The Internal Assessment for Chemistry has given me the right set of circumstances and
opportunities to research and gain additional insight and knowledge into this topic.
With two billion people worldwide affected by it, iron deficiency is, by far, the most common nutritional
deficiency in the world (Anaemia, 2023). It is safe to presume that an innumerable amount of people
around the world store their supplements in storage compartments and powder rooms. Despite where you
are around the world, it is natural for storage compartments to begin to humidify over time. Humidity is
known to deteriorate capsules and tablets, so understanding how and in what ways humidity affects the
composition and stability of iron tablets is crucial in the pharmaceutical context. Its importance is evident
as changes can lead to direct implications on the effectiveness of the supplements and tablets in treating
iron-deficiency anemia (The Effects of Humidity on Pharmaceuticals, 2018). As anemia is a common
health issue globally, iron tablets are a necessity in healthcare to ensure advancements in human health.
To treat iron-deficiency anemia, iron tablets are a widely attributed solution. Therefore, ensuring the
integrity of iron tablets under numerous conditions, including humidity, is vital for maintaining their
efficiency.
Although varied experiments have been conducted surrounding the topic of calculating percentage of
iron, an in depth study, such as this one, with the specific study of the effect of humidity on percentage of
iron in iron tablets, has not been extensively studied. This approach aims to fill in that gap and will
provide supplementary information and insights into a practical issue. A capacious and substantial study
is required to affirm and solidify results, which this experiment aims to achieve.
[Background]
Iron
Iron is a crucial component of our lives on a day to day basis as it plays a major role in immunity, cell
division, metabolism, and oxygen transport within our bodies. Iron, as well as many other transition
metals, is known to have many diverse oxidation states, a number of the electrons an atom can lose or
gain to create a bond with another atom, as there is no outstanding increase in ionization energy in
transition metals. Although there are different oxidation states of iron, the most stable form is its ferric
state, Fe3+ (Which Is More Stable Fe2+ or Fe3+?, n.d.). Another common form is the ferrous state, Fe2+,
which will be utilized in this experiment. These various oxidation states of iron allow it to be
implemented in reduction and oxidation reactions and allow it to be used for vital functions in the human
body including energy metabolism and the catalysis of enzymatic reactions.
Humidity
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Humidity is the measure of water vapor in the air. If there is a lot of water vapor present in the air, the
humidity will be high, which causes it to feel damp outside. When water evaporates after sunlight warms
its surface, water rises and, thereafter, disseminates into the surrounding air. This ultimately leads to
humidity.
Humidity is blamed for various negative effects including mold inside homes–usually in the bathrooms,
where, due to showers, is wet most of the time–, interrupts electric currents, and causes a loss of power.
More importantly, however, moisture and humidity are known to compromise the effectiveness and
potency of many pharmaceutical products such as tablets and lead to degradation or even toxicity (The
Effects of Humidity on Pharmaceuticals, 2018).
Exposure to humid weather can break down both over-the-counter and pharmaceutical drugs and lead to
less effectiveness of the products, interfering with patients' dosage amounts. This study uses this prior
knowledge to test a more accurate and unambiguous representation of the alterations that arise in
percentage of iron subsequent to its exposure to humidity.
Redox
A redox reaction, also known as an oxidation-reduction reaction, is a type of chemical reaction in which a
transfer of electrons between two species occurs. A redox reaction embodies any chemical reaction in
which an oxidation number of a molecule, the charge a molecule would have if the compound was
composed of ions, changes or alters by gaining or losing electrons. Oxidation-reduction reactions are
pivotal to a multitude of basic functions of life, which include: respiration, combustion, corrosion or
rusting, and even photosynthesis.
Prior to the discovery of electrons, the word ‘oxidation’ referred to the addition of
oxygen onto a compound. For example, in the diagram to the right, oxygen is being
added to hydrogen gas (H2) from carbon dioxide (CO2) and to Copper (Cu) from
oxygen gas (O2). This was referred to as oxidation. ‘Reduction’ originated from the
Latin stem meaning “lead back” (Oxidation-Reduction Reactions, 2023).
Subsequent to the discovery of electrons, the meaning of ‘oxidation’ shifted into the
process where an electron is removed from a molecule or atom during a chemical
reaction. Reduction is the opposite; where an electron is gained by one of the atoms involved in the
reaction between two compounds. If the oxidation number of an atom increases, the atom is oxidized.
When the oxidation number decreases, the atom is reduced. The atom that is oxidized in a reaction is the
reducing agent or, in other words, an atom that loses electrons to other atoms or compounds in an
oxidation-reduction reaction and becomes oxidized to a higher valence state. Therefore, an atom that is
reduced is known as the oxidizing agent. For example, in the image below, although the total number of
electrons remained unchanged, copper’s oxidation number decreased from +2 to 0, signifying reduction,
and the oxidation number of magnesium increased from 0 to +2, representing oxidation. Additionally, in
this situation, magnesium would be named as the reducing agent and copper the oxidizing agent.
Titration
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A titration is a method used in order to determine the concentration of an unknown solution when given a
known substance’s concentration. In this procedure the known solution is added from a buret, a
volumetric glassware used for measuring the amount of a liquid in analytical chemistry, into a set quantity
of an unknown solution– the analyte. The substance added into the buret is known as the titrant. In a
titration, the titrant gets slowly added into the analyte until the reaction reaches neutralization, when the
reaction is complete. This is often suggested by an unambiguous, stable color change
(Oxidation-Reduction Reactions, 2023).
The most common category of titrations are redox titrations, the type that are being used in this
experiment. A redox titration is based on the oxidation-reduction reaction between the titrant and the
analyte and is used to establish the concentration of an unknown solution. The redox method is being
utilized here as we are determining the concentration and, thus, deducing the percentage of iron present in
a tablet of ferrous sulfate.
In this study, the oxidizing agent used is a permanganate ion (MnO4-). In redox titrations, this is often
added in the form of potassium permanganate (KMnO4). The substance that will oxidize Fe2+ into its more
stable form, Fe3+, resulting in a color change. The permanganate ion in the experiment will act as a
self-indicator as it is a strong oxidizing agent and has a solution color of purple. In this situation, the
oxidation state of manganese changes from 7+ to 2+ as shown in the reaction equation below. In this
titration, a persisting pink/purple hue indicates excess permanganate after all Fe2+ ions have reacted. The
half-reactions and overall reaction are represented as follows:
Oxidation half-reaction: 5 * (Fe2+(aq) → Fe3+ (aq)+ e-)
Reduction half-reaction: MnO4-(aq)+ 8H+(aq) + 5e- → Mn2+(aq) + 4H2O (l)
Overall reaction: MnO4- (aq) + 5Fe2+(aq) + 8H+(aq) → Mn2+(aq) + 5Fe3+(aq) + 4H2O (l)
Hypothesis
The hypothesis for this experiment is that as the humidity level exposure of iron tablets increases, the
percentage of iron (Fe2+) available in the iron tablet will decrease. This is because it is known that an
increased humidity can cause the oxidation rate of Fe2+ to Fe3+ to increase, which results in a decrease of
the concentration of Fe2+. Therefore, it can be hypothesized that the iron tablet with no direct exposure to
humidity will exhibit a higher concentration of Fe2+ than that of the 96 hour humidity exposure level.
[Variables]
Table 1: shows the independent variable, how and why it was varied.
Independent Variable
Time of ferrous sulfate
tablets exposed to humidity
in a humidifier
How it was varied
Why it was varied
The humidity exposure levels used in this
The effect of humidity on the percentage of Fe2+ in
experiment are 0 hours, 24 hours, 48 hours, 72
the iron tablets can be investigated. A constant
hours, and 96 hours. These tablets (6 in each interval of 24 hours is used to theoretically display a
humidity level) were placed in a humidifier for constant change in Fe2+ concentration as humidity
their respective time limits.
exposure increases.
Table 2: shows the dependent variable, how and why it was measured.
Dependent Variable
How it was measured
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Why it was measured
The percentage of Fe2+ that is
present in ferrous sulfate
tablets
The volume of KMnO4 required to completely
The change in the percentage of Fe2+ in the iron
oxidize Fe2+ in the iron tablet solution was
tablets as humidity exposure increases can be found,
measured by titration. This volume was
answering the research question.
obtained by taking the final - initial reading
from the burette.
Table 3: shows the controlled variables, how and why they are controlled.
Controlled
Variable
How It Is Being Controlled
Why It Is Being Controlled
Quantity of
Iron Tablets
Always using 6 iron tablets for
each humidity level.
To ensure uniformity in the amount of iron being exposed to different humidity
conditions. This is important because a trial with more or less than 6 tablets could
have lower Fe2+ percentages and would lead to an imbalance in the experiment.
Mass of Iron
Tablets
Each iron tablet is 65mg. Made
via manufacturing processes.
To maintain the amount of iron constant across all trials for an accurate data
comparison.
Humidifier
Settings
The humidifier is set to run for
24-hour intervals at the specified
humidity levels.
To standardize the exposure period and humidity conditions for each group of
tablets. Different intervals would lead to some intervals being more humid than
others.
Humidity
Levels
The level of humidity within the
humidifier is kept consistent
across all experiments.
To ensure the effect observed is due to the duration of exposure, not the intensity of
humidity. More or less intense humidity would lead to different implications on the
iron tablets.
Volume and
Concentration
of Sulfuric
Acid
Using 100cm³ of sulfuric acid
solution at 1.0 mol dm-³ for all
samples.
To ensure that the reaction medium is consistent for dissolving the iron tablets,
allowing us to have comparable results. Different concentrations would lead to
significant variances in the results.
Preparation of
Potassium
Permanganate
Solution
Weighing 2.37051g of KMnO₄
and dissolving it in a 1000 cm³
volumetric flask for a 0.015 mol
dm⁻³ solution.
To maintain the consistency of the KMnO₄ solution's concentration for all titrations,
ensuring uniform reaction conditions. If the preparation of the potassium
permanganate solution was performed in a different way, it is possible that the
solution could be different.
Volume of
Iron Tablet
Solution for
Titration
Drawing 25cm³ of the iron tablet
solution for each titration.
To ensure that the volume of the solution being titrated is the same, allowing for
accurate comparison of the potassium permanganate needed. More or less volume of
the iron tablet solution would lead to an improper representation of the effects of
humidity.
Volume of
Sulfuric Acid
Added to
Conical Flask
Adding 10cm³ of sulfuric acid to
the conical flask in each titration.
To maintain the acid concentration during the redox reaction, ensuring the
conditions are identical for each titration. A change in the sulfuric acid would alter
the required volume of potassium permanganate to reach its endpoint.
Use of
Deionized
Water
Consistent use of deionized water
for preparing solutions and
rinsing apparatus.
To prevent additional elements from interfering with the reactions or measurements,
ensuring purity and consistency of the experimental conditions. Using other sources
of water could lead to molecules affecting the results of the trials.
Titration
Process
Standardizing the method of
titration, including the use of a
magnetic stirrer and the endpoint
detection method.
To ensure comparability across all trials by using the same technique to determine
the endpoint of the reaction. This ensures that there are no other changes within the
methodology that could affect that specific trial differently.
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Measurement
Techniques
Using analytical balances for
weighing, volumetric flasks for
solution preparation, and burettes
for titration.
To achieve high precision and accuracy in measurements, crucial for the reliability
of the experiment's results as usage of other balances would lead to an unspecified
amount of the weighted solution.
[Materials and Apparatus]
Chemicals and Materials
●
●
●
●
30 iron tablets (65mg)
Potassium Permanganate Powder
(2.37051 g)
Sulfuric Acid Solution – H₂SO₄
(1.0 mol dm-3)
Deionized Water
Glassware
●
●
●
●
●
●
●
●
●
●
●
●
●
1 x 1000cm3 Volumetric Flask and
Stopper (±0.1cm3)
1 x 250cm3 Volumetric Flask and
Stopper (±0.1cm3)
1 x 100cm3 Graduated Cylinder
(±0.1cm3)
2 x 250cm3 Beaker (±0.1cm3)
1 x 50cm3 Burette Stand and Clamp
(±0.2cm3)
1 x 25cm3 Pipette (±0.1cm3)
1 x 100cm3 Conical Flask (±0.1cm3)
5 x Test Tubes
1 x 3in x 3in White Tile
1 x Pestle and Mortar
1 x Magnetic Stirrer Hot Plate
1 x Storage Container
1 x Stir Bar and Stir Bar Retriever
Laboratory Equipment
●
●
●
●
●
1 x Analytical Balance (±
0.0001g)
1 x Filter Funnel and Filter
Paper
1 x Weighing Boat
1 x Ring Stand
1 x Humidifier
[Safety]
The following are hazards and safety issues prevalent in this experiment along with a solution to
minimize these risks.
Potassium Permanganate (KMnO4) – Contact with this substance could lead to potential skin
irritation and eye damage. Inhalation of this substance can irritate the lungs and potentially lead to
shortness of breath. To minimize the risk, safety goggles as well as gloves are required for this
experiment. Usage of a lab apron is also recommended to prevent skin contact with the substance.
Additionally, proper ventilation should be present in the laboratory. If potassium permanganate
touches the skin, immediately wash it off with water. If there is a direct contact with the eyes, use
an eye washer immediately (SAFETY DATA SHEET, 2009).
Sulfuric Acid (H2SO4) – This substance is a highly corrosive substance and an irritant to the skin
and eyes. Inhalation of this substance can also lead to irritation of the lungs and potential
shortness of breath. To minimize the risk, gloves should be worn at all times during this
experiment to prevent skin contact with the substance. Additionally, proper ventilation should be
present in the laboratory. If an acid touches the skin, immediately wash it off with water. If there
is a direct contact with the eyes, use an eye washer immediately (SAFETY DATA SHEET, 2009).
Handling and Usage of Glass Apparatus – Glass apparatus, such as the burette and conical
flask can be shattered if not handled with care and lead to injury if dropped. This risk can be
minimized by ensuring that no glass apparatus are near the edges of the workstation and prone to
being dropped. In case of an emergency, inform your supervisor and seek medical attention.
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[Methodology / Procedure]
Although a procedure that directly replicated this experiment was unable to be found, the methodology of
a similar experiment, which was about finding the percentage of iron in iron tablets, outlined a procedure
similar. Initially, the iron tablets were humidified using the high level of the humidifier. After the
humidifier had completed 24hrs with the tablet for the rough titration of this experiment, the tablets
appeared bursted. It was decided that keeping the tablets for our higher humidity levels would lead to the
tablet being improper and invalid for experimental purposes. This same issue occurred when we dropped
the humidity level to medium. It was pronounced that the low level of the humidifier should be used in
this experiment as, subsequent to the humidifier being on the low level, the tablets had not bursted,
indicating that the low level of the humidifier should be utilized.
Part 1 - Preparation of Iron Tablets (65mg)
1. Place 6 iron tablets onto an evaporating dish each of the 5 humidity levels (0hrs, 24hrs, 48hr,
72hrs, 96hrs). Label each.
2. Place the iron tablets (65mg) into a humidifier with a plastic container on top. Leave the container
in a slanted position allowing some air to escape (without this step, the iron tablet would melt).
3. Turn on the humidifier and set the time for 24 hour intervals. Each time a 24 hour interval passes,
remove its respective tablet group (after 24 hours, remove the 24-hour tablets; set humidifier for
another 24 hours and remove 48-hour tablets after its interval is done, etc. up to 96 hours)
4. Upon reaching the target humidity, turn off the humidifier, remove the storage container, and
collect the iron tablets (65mg).
5. Crush the iron tablet using the pestle and mortar. Use 100cm3 of the sulfuric acid solution (1.0
mol dm-3) to the crushed tablets as needed to create a homogenous solution. Repeat for all tablets
and humidity levels.
Part 2 - Creation of the Potassium Permanganate (KMnO4, 0.015 mol dm-3) Solution
6. Place a weighing boat onto an analytical balance. Zero this weight.
7. Weigh out 2.37051g of Potassium Permanganate (KMnO4) using the analytical balance.
8. Put the 2.37051g of Potassium Permanganate (KMnO4) into a 1000 cm3 volumetric flask using
deionized water to assist in washing it down, preserving the most as possible.
9. Using deionized water, make sure that none of the Potassium Permanganate (KMnO4) solution is
on the inside edges of the volumetric flask. Fill the volumetric flask about half way with
deionized water.
10. Put the stir bar into the volumetric flask using the stir bar retriever to not cause any damage to the
glassware.
11. Turn on the magnetic stirrer hot plate and turn the “Stir” section to Low-Medium. This should
cause the stir bar to rapidly revolve leading to the Potassium Permanganate (KMnO4) solution to
mix. Leave this on for a couple minutes to thoroughly mix the solution.
12. After the solution has been mixed, fill the solution just below the calibration line as the stir bar is
still inside.
13. Remove the stir bar and rinse it with a small amount of deionized water so the bottom of the
meniscus reaches the calibration line. This is to make sure that all of the Potassium Permanganate
(KMnO4) is inside the volumetric flask.
14. Place the stopper onto the volumetric flask. This is the prepared Potassium Permanganate
(KMnO4) solution.
Part 3 - Preparation of the Apparatus
15. Transfer the crushed iron tablet solution from the pestle and mortar into a 250 cm3 volumetric
flask. Add the remainder of the 100cm3 of the sulfuric acid solution (1.0 mol dm-3) into the
volumetric flask to ensure all of the crushed iron tablet is transferred.
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16. Fill the 250 cm3 volumetric flask with deionized water until the bottom of the meniscus is reached
at eye level. Note that deionized water does not affect the endpoint of the titre as it acts only as a
solvent.
17. Attach the stopper to the volumetric flask and mix solution back and forth horizontally
roughly 20 times to ensure a homogenous solution is reached.
18. Transfer the 250 cm3 iron tablet solution from the volumetric flask into the 250cm3 beaker.
19. Draw deionized water into the 25 cm3 pipette. This acts as a rinsing mechanism.
20. Expel the deionized water out of the pipette.
21. Repeat steps 19-20 with the iron tablet solution to ensure that the measurement is not
diluted.
22. Draw 25cm3 of the iron tablet solution into the pipette using the bottom of the meniscus as
reference at eye level.
23. Transfer the 25cm3 of the iron tablet solution from the pipette into a 100cm3 clean and dry
conical flask. Ensure the entirety of the solution is expelled.
24. Add 10cm3 of the sulfuric acid solution into the 100cm3 conical flask. Note this is the
second time sulfuric acid has been utilized in this experiment.
25. Rinse and clean the burette with deionized water. Make sure to empty the burette after rinsing is
completed.
26. Rinse the burette with the potassium permanganate solution once. Make sure to empty the burette
after rinsing is completed.
27. Attach the burette to the clamp on the ring stand. Place a funnel on top to assist in adding the
solutions.
28. Fill the burette with the potassium permanganate solution (0.015 mol dm-3) until the solution
reaches a couple of milliliters above the 0cm3 mark. Make sure the tap on the burette is closed–in
a horizontal position.
29. Slowly release the potassium permanganate solution (0.015 mol dm-3) into a 250cm3 waste
beaker until the solution reaches 0cm3 at the bottom of the meniscus at eye level.
30. Place a 3x3 inch white tile on top of a magnetic stirrer hot plate to ensure endpoint
accuracy. Place the 100cm3 conical flask on top of the white tile and carefully drop the stir
bar into the flask.
Part 4 - Redox Titration
31. Turn the magnetic stirrer hot plate on to medium speed and slowly release the potassium
permanganate solution (0.015 mol dm-3) by fixing the tap into a vertical position. To ensure
accuracy of the experiment, make sure to slowly drop the potassium permanganate solution
(0.015 mol dm-3).
32. Continue titrating the solution until a pale pink/purple color has been reached. Quickly
return the tap of the burette into a horizontal position to prevent the further release of the
potassium permanganate solution (0.015 mol dm-3). This indicates the endpoint of the
reaction.
33. Record the cm3 value from the burette. This represents the cm3 amount of potassium
permanganate solution (0.015 mol dm-3) needed to fully oxidize with iron in the solution.
34. Repeat this titration for the remaining humidity exposure levels (0hrs, 24hrs, 48hr, 72hrs,
96hrs), to obtain 6 trials at each humidity level.
Ethical and Environmental Considerations
There are no ethical considerations in this investigation. The used iron tablets and their respective
solutions should be disposed of properly into waste containers, as it could lead to an unfavorable effect on
its surroundings and the environment. Used chemicals should also be disposed of properly as the
supervisor in the lab suggests, as they may cause environmental harm if thrown into inappropriate areas.
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Quantitative Data
1. Iron tablets' physical appearance slightly changes over the different humidity levels.
2. The color of the potassium permanganate solution is a deep purple before titration.
3. A pale pink/purple color indicates the endpoint of the titration.
4. Crushing the tablets results in a fine powder that slightly varies in color and texture based on
humidity exposure.
5. The sulfuric acid solution turns from clear to white when dissolving the iron tablet powder.
6. The potassium permanganate solution's color gradually fades as it reacts during titration.
7. The consistency of the iron tablet solution changes after adding sulfuric acid.
[Data Tables and Graphs]
Quantitative Data
Table 4: shows the volume of KMnO4(aq) added to the iron tablet solution for each humidity exposure
level for each trial, as well as the average volume and standard deviation
Time of Iron
Mean Titre
Standard
Volume of KMnO4(aq) added (cm3)
Tablets in
Average
Volume
Deviation
Humidifier
Uncertainty
3
3
(± 0.01 cm ) (± 0.01 cm )
(hours)
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
(±cm3)
0
12.10
12.00
12.40
13.50
12.20
12.44
0.61
0.75
24
11.00
10.90
11.00
10.80
11.00
10.94
0.09
0.10
48
10.10
9.90
10.10
10.00
10.50
10.12
0.23
0.30
72
8.70
9.00
9.10
11.30
10.50
9.72
1.12
1.30
96
8.50
7.50
8.70
7.80
8.10
8.12
0.49
0.60
[Calculations]
Calculations were evaluated using a TI-84 Plus C Silver Edition graphical calculator. All example
calculations were used from Trial 1: 0 hours. Refer to Table 1 above.
1. Calculating the amount of KMnO₄ powder needed to make 1000 cm3 of 0.015M KMnO₄ solution:
1000 cm3 = 1 dm³ and M=mol dm-³
𝑚𝑜𝑙
0.015 = 1 = 0.015 = 0.015 moles of KMnO₄ powder
Calculating grams using stoichiometry:
𝑚𝑜𝑙
(39.0983 + 54.938043 + 63.9976)
0.015 1 ᐧ
= 2.37050914 grams of KMnO₄ powder required
1 𝑚𝑜𝑙
2. Calculating the titre volume:
Endpoint - Startpoint = Titre Volume
Example Calculation:
(12.10 ± 0.05) - (0.00 ± 0.05) = 12.10 ± 0.1 cm3
3. Calculating the mean titre volume:
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Mean Titre Volume =
𝑆𝑢𝑚 𝑜𝑓 𝑡ℎ𝑒 𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑅𝑒𝑎𝑐𝑡𝑒𝑑 𝐾𝑀𝑛𝑂4
𝑇𝑜𝑡𝑎𝑙 𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑇𝑟𝑖𝑎𝑙𝑠
Example Calculation:
12.10 + 12.00 + 12.40 + 13.50 + 12.20
Mean Titre Volume =
= 12.44 cm3
5
4. Average Uncertainty Calculations”
𝐻𝑖𝑔ℎ𝑒𝑠𝑡 𝑣𝑎𝑙𝑢𝑒 𝑖𝑛 𝐼𝑉 𝑔𝑟𝑜𝑢𝑝 − 𝐿𝑜𝑤𝑒𝑠𝑡 𝑣𝑎𝑙𝑢𝑒 𝑖𝑛 𝐼𝑉 𝑔𝑟𝑜𝑢𝑝
2
= 𝑎𝑣𝑒𝑟𝑎𝑔𝑒 𝑎𝑏𝑠𝑜𝑙𝑢𝑡𝑒 𝑢𝑛𝑐𝑒𝑟𝑡𝑎𝑖𝑛𝑡𝑦 𝑜𝑓 𝐼𝑉 𝑔𝑟𝑜𝑢𝑝
Example Calculations:
13.50−12.00
2
=
3
3
1.50
→ 0. 75 → 𝑎𝑣𝑒𝑟𝑎𝑔𝑒 𝑢𝑛𝑐𝑒𝑟𝑡𝑎𝑖𝑛𝑡𝑦 𝑜𝑓 12. 44 𝑐𝑚 ± 0. 75 𝑐𝑚
2
5. Calculating the standard deviation of the titre volume:
σ=
2
Σ(𝑥−𝑚)
𝑁−1
x = the set of numbers
m = mean
N = size of the set
σ=
2
2
2
2
2
(12.10−12.44) +(12.00−12.44) +(12.40−12.44) +(13.50−12.44) +(12.20−12.44)
5−1
= 0.61 cm3
6. Calculating the number of moles of reacted KMnO4:
n=c×v
n = number of moles
c = concentration of KMnO4 solution
v = volume of KMnO4 (dm3)
Number of moles of reacted KMnO4:
0.015
n(KMnO4) = 1000 × 12.44 = 1.866 × 10-4 per 12.44 cm3
7. Using the reaction below (background information section), we can determine the moles of Fe2+:
MnO4- (aq) + 5Fe2+(aq) + 8H+(aq) → Mn2+(aq) + 5Fe3+(aq) + 4H2O (l)
The molar ratio between KMnO4 and Fe2+ can be evaluated from the coefficients of both
compounds in the formula above. Hence, the molar ratio between KMnO4 and Fe2+ is 5:1.
n(Fe2+) = 1.866 × 10-4 × 5 = 9.33 × 10-4 per 25 cm3 of Fe2+
2+
To find molarity of Fe :
−4
9.33 × 10
25
× 1000 = 0.03732 mol Fe/dm3
Molar mass of Fe2+ is 55.85 (as expressed in the IB Chemistry Data Booklet)
Thus, the mass of iron from a 25 cm3 pipette, which was originally obtained from a 250 cm3 (1/10th
of original) volumetric flask is:
0.03732 × 55.85 = 2.084322 g/dm3 ÷ 4 = 0.521 g/250 cm3 of iron
The procedure indicates there are 6 tablets crushed. The mass per tablet it:
0.521 ÷ 6 = 0.0868 g of Fe per tablet
To find the percentage of iron:
𝑀𝑎𝑠𝑠 𝑜𝑓 𝐹𝑒 𝑖𝑛 𝑎 𝑡𝑎𝑏𝑙𝑒𝑡
% Fe in one tablet = 𝑀𝑎𝑠𝑠 𝑜𝑓 𝑎 𝑡𝑎𝑏𝑙𝑒𝑡 × 100
0.0868
0.33
= 26.30 % Fe in iron tablet
Processed Data:
Table 5: shows the average Fe2+ content in the iron tablets and their respective percentages.
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Time of Iron Tablets in Humidifier
(hours)
Fe2+ Content in Iron
Tablets (g)
Percentage of Fe
in the Iron Tablets (%)
0
0.0868
26.32
24
0.0764
23.14
48
0.0707
21.41
72
0.0679
20.56
96
0.0567
17.18
Graphs
Graph 1
[Analysis]
The purpose of the experiment conducted was to determine if humidity impacts the iron content of ferrous
sulfate tablets by evaluating how different lengths of time being exposed to humidity impact the percent
of iron in these supplements. Data collected via redox titration, a quantitative method selected because of
its accuracy and precision in chemical analysis, uncovered a very clear trend. As the length of time
exposed to humidity increased, the volume of potassium permanganate needed to reach the endpoint of
the titration decreased. This consistent trend is indicative of a change in the availability of iron within the
tablets whether it is through degradation or oxidation and, thereby, how effective it is as a supplement.
The decrease in iron content as a function of increasing humidity exposure can be attributable to several
chemical processes. Iron (especially in its ferrous form, Fe2+) is highly susceptible to oxidation as
aforementioned, particularly in the presence of moisture. The presence of water vapor can greatly
facilitate the oxidation of Fe2+ to Fe3+, which makes this form of the element far less absorbable by human
bodies and hence ineffective in treating conditions such as iron-deficiency anemia. It’s clear from these
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observations that the pharmaceutical and health implications of improper storage of iron supplements in
humid environments should not be overlooked. As far as the data is concerned, the percent iron decreased
systematically across humidity exposure times; from 0.0868g/tablet in the 0-hour (control) group to
0.0567g/tablet in the 96-hour group. This not only corroborates our hypothesis with empirical evidence,
but it suggests just how significant environmental conditions can be on the stability of pharmaceutical
products. All of the IV level trials followed a clear trend, emphasizing the effects of humidity on iron
tablets. A mathematical representation (i.e. a model) of this degradation is demonstrated by the calculated
iron contents across humidity exposure times in, which imply a proportional relationship between time of
humidity exposure and iron degradation rate.
The data clearly shows that there were no outliers in the trials conducted. Although there were random
errors, there was an overall consistency and precision within each IV level. Random errors led to clearly
higher or lower values than the remaining in the IV level. The effect of random errors were minimized by
increasing the trials per IV level and calculating the average between the trials. For example, in the 0 hour
IV level, Trial 2 required 12.00ml of the potassium permanganate, whereas the Trial 4 of the same IV
level required 13.50ml. These small discrepancies may have been due to improper calibration of the
apparatus or endpoint determination of the experimenter.
Furthermore, the accuracy of this experiment is exemplified by the R2 value presented on the Graph 1. R2
values range between 0 and 1 and emphasize the accuracy of the data points given to the best fit line. The
closer the value is to 1, the more accurate and proportional the results. As we can see on the graph, the R2
value displayed is 0.962. This high value compliments the accuracy of this experiment. The reasons for
the 0.038 difference from a 1 R2 value may be due to random errors throughout this experiment.
It's worth noting, however, that the absolute humidity exposure levels in the test weren't necessarily
representative of real-life storage conditions. The point of the experiment was to replicate what high
humidity did to iron tablets, and in homes or pharmacies, you will most likely not run into humidity high
enough to mimic rainforest conditions. So, while the findings emphatically underline some of the risks
associated with improper storage, they're not a commentary on environmental exposure for the typical
supplement.
Table 6: Sources of Error
Error Type
Potential Impact
Mitigation Strategy
Systematic Errors
Calibration of Instruments
May cause inaccurate measurements.
Titration Technique
Variability in endpoint detection.
Humidity Control
Inconsistent humidity levels.
Use of controlled environment chambers.
Chemical Purity
Impurities in reagents affecting reactions.
Utilize high-purity chemicals and verify sources.
Limitations in measuring equipment accuracy.
Employ higher precision instruments where possible.
Instrument Precision
Regular calibration and verification of equipment.
Standardize technique and use of automatic titrators.
Random Errors
Tablet Composition
Variability in iron content per tablet.
Use tablets from the same batch and manufacturer.
Environmental Variations
Fluctuations in lab conditions (temperature).
Conduct experiments in a stable, controlled setting.
Measurement Variability
Misreading of measurements.
Use digital measuring devices to reduce human error.
Table __: Strengths
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Strengths
Significance
Controlled Variables
Precise management of experimental variables like temperature and tablet mass focused the
investigation on the effects of humidity alone
Comparison with Other Iron Forms
Methodological Consistency
The consistent application of redox titration across trials ensured the reliability of data
regarding the impact of humidity on Fe2+ content.
Table 7: Weaknesses
Weaknesses
Significance
Improvement
The subjective nature of titration endpoint
Utilizing objective endpoint detection methods, such
Endpoint Determination determination could introduce significant variability. as colorimetry, could significantly enhance accuracy.
Tablet Crushing
Variability in the crushing process could impact the
surface area exposed, influencing the dissolution rate
and, consequently, the reaction completeness.
Standardizing the procedure for tablet crushing to
ensure uniform particle sizes would yield more
consistent outcomes.
Further investigations could significantly expand the understanding of iron supplement stability and the
mechanisms behind iron degradation. Potential areas for future research include:
Table 8: Extensions of Research
Research Extension
Rationale
Effect of Temperature on Iron
Stability
To determine if higher temperatures accelerate iron degradation.
Comparison with Other Iron Forms
Assessing the stability of different iron formulations under similar conditions.
Long-term Humidity Exposure
Study
Investigating the effects of prolonged humidity beyond 96 hours.
Protective Coatings on Tablet
Stability
Evaluating if coating technologies can enhance the resilience of iron tablets to environmental
conditions.
Bioavailability Studies
Examining the impact of degraded iron tablets on iron bioavailability in the human body.
[Conclusion]
This study emphasizes the critical role that humidity plays in the stability of ferrous sulfate tablets and
therefore, the importance of appropriate storage conditions for maintaining therapeutic efficacy. As iron in
its Fe2+ state is used in blood, it is important to acknowledge all possible factors leading to its loss. It is
also important to note that while this experiment offers fascinating insights, it is also important to
acknowledge sources of error, as the humidity exposures the researchers created may not be realistic for
some storage situations. Sun, air conditioning, a jar of silica packets, pieces of furniture, and dead skin,
for example, can all affect the conditions in some of the more unorthodox places iron tablets can be stored
(so all of these would be worth testing, too). The testing conducted was indeed designed for a worst-case
scenario, not everyday exposure. By building upon such a sound base of information, future research will
continue to expose the fascinating and complex ways pharmaceuticals interact with their surroundings and
guide the development of more resilient and potent treatments for iron-deficiency, and potentially trials
focused on more mild conditions, but still more realistic humidity ranges that can lead to product
packaging, and to instructions for storage, that are useful and comprehensible to consumers and health
professionals.
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