Name(s):
Period:
Date:
Aspirin Titration
HASPI Medical Chemistry Lab
Background/Introduction
Aspirin comes in 3 strengths, which can be used for different reasons depending on your medical needs.
Low Dose Aspirin (81mg)
Low Dose aspirin, also known as "Baby" aspirin, is not actually for babies. It's used
as an antiplatelet drug. Platelets are the substance in your blood that cause your
blood to clot. They normally move around individually, and when you bleed your
body sends a chemical signal out which causes the platelets to gather together,
which is called aggregation. Aspirin binds irreversably to the platelet which inhibits
aggregation. This means that it stops that platelets from gathering to create a clot.
A heart attack or stroke occurs when a clot gets stuck in one of your vessels
(arteries, veins or cappilaries), which means that everything down stream stops
getting blood. This cuts off the oxygen supply and the cells die. In your heart,
this causes a heart attack, as the cardiac cells die. In the brain this causes a
stroke because brain matter dies. If a person experiences a stroke or heart
attack, the doctors only have about one hour to break up the clot before
permanent damage occurs. An unhealthy diet or genetic predisposition can
cause your arteries to become more narrow due to plaque buildup, increasing
your chance of stroke or heart attack.
By taking small doses of aspirin every day you are able to keep clots from forming so that there is a
reduced risk of heart attack and stroke. The small dose reduces your side effects, while still binding to
the small amount of new platelets your body forms every day. The extra aspirin that does not bind to the
platelets is excreted through your urine within just a few hours of taking it, so you have to take another
small dose the next day to inhibit with any new platelets.
Regular and Extrastrength Aspirin (325 to 500mg)
Aspirin is known as an NSAID. This stands for Non-Steroidal AntiInflammatory Drug. Aspirin can bind to an enzyme called COX-2 which
causes inflammation and Prostaglandins which also cause inflammation and
they help send pain signals to the brain. When aspirin binds to these
substances they can't work so inflammation is reduced and the brain does
not get as strong of a pain signal. The amount of aspirin in a regular or extra
strength capsule will allow for a high enough concentration of aspirin in the
cells to reduce the pain signal and reduce inflammation.
More Uses of Aspirin
Interestingly, baby aspirin has been found to have a number of benefits. When studying groups of people
who took baby aspirin for heat issues (a regimin of 81mg/day) , researchers found a reduced incidence of
cancer, an increase in fertility
It is thought that these benefits may be because aspirin reduces inflammation and it increases blood flow.
Inflammation may contribute to the development of cancer, and fertility can be enhanced by increased
blood flow.
*********, HASPI Medical Chemistry Lab ###
1
Name(s):
Period:
Date:
Why we use Titration
Titration is a way to use a very controlled reaction to quantify the amount of reactant present. In the case
of medications, we can use this to determine the amount of medicine in a tablet. Because aspirin is an
acid, we can neutralize it drop by drop with a known concentration of basic solution. The color will
change when the reaction is complete, so that every aspirin molecule has reacted with NaOH. We can
calculate the amount of aspirin using the amount of NaOH needed.
An indicator is added to the solution, which will change colors when the neutralization is complete. In
this case we will use phenylthalein which turns pink when it becomes basic.
Companies can use this technique for quality control. Testing random medicine samples to make sure
that the right concentration is going into the tablets is essential to make sure it is safe to take the
medication.
Additionally, a medicine can break down over time. Although aspirin has an expiration date, it actually
starts to break down right away... a little at a time. A byproduct of aspirin disintigration is vinegar, so
sometimes older aspirin will smell like vinegar. This byproduct can also increase side effects, so it is
always best to use fresh aspirin, and it's best not to use it after the expiration date.
Scientists can take a bottle of aspirin and test the tablets over time using titration to see how quickly the
medicine breaks down. This helps to determine a proper expiration date for a medication, so that they
can make sure that consumers are able to use it safely.
PreLab Questions
1. This reading introduced new vocabulary. Using hints from the sentence they are found in or using a
dictionary, define the following terms:
antiplatelet
inflammation
aggregate
excreted
irreversibly
inhibit
vessel
cardiac
stroke
titration
heart attack
indicator
platelet
2. If you have a headache, what type of aspirin should you choose?
3. What are two reasons to take low dose aspirin every day?
4. Name a use for titration
5. If we had a basic medication, what kind of solution would you need in order to titrate it.
6. What kind of chemical is used to show when the neutralization is complete.
*********, HASPI Medical Chemistry Lab ###
2
Name(s):
*********, HASPI Medical Chemistry Lab ###
Period:
Date:
3
Name(s):
Period:
Date:
Aspirin Titration
HASPI Medical Chemistry Lab
Objectives
1. Calculate the number of moles of aspirin in each of the tablets
2. Calculate the number of moles of NaOH needed to titrate the aspirin
3. Calculate the volume of 0.10M NaOH required to titrate the aspirin
4. Complete titrations of each aspirin to find the experimental value
4. Compare the predicted amount NaOH with the amount used experimentally
Scenario
The active ingredient in aspirin is acetyl salicylic acid. Different strengths of
aspirin are based on the amount of active ingredients that they contain.
Titration is a way to determine how much acid is in a solution by adding just
enough base, of a known concentration, to neutralize the acid. At the point of
neutralization, the number of moles of acid (H+) is combined with an equal
number of moles of base (OH-).
You will perform a titration by dispensing a base of known volume and
concentration into an acid solution of known volume but an unknown concentration. The aspirin will
be titrated against a standard solution of base, 0.100 M NaOH. This base will be dispensed from a
burette into a beaker containing the dissolved (in ethanol) acetyl salicylic acid and phenolphthalein
indicator, which appears as a faint pink color in basic solutions
In this lab you will be given three types of aspirin, baby aspirin containing 81mg of aspirin, regular
strength aspirin containing 325mg of aspirin and extra strength aspirin containing 500.mg of aspirin.
First you will calculate the amount of NaOH you will need in order to do the titration, then you will
proceed with the titration and find your error.
Materials





1 baby aspirin
1 regular strength aspirin
1 extra strength aspirin
Mortar & Pestle
25mL or 50mL graduated cylinder




Pipette
1 buret
Ring stand and buret clamp
0.10M NaOH




Phenylthalein
125mL Erlenmeyer flask
DI water
Ethanol
Predictions
We are going to begin by calculating the volume of NaOH which we expect to use. The way we
predict the amount of reactants needed is through
stoichiometry.
First take a look at the reaction:
HC9H7O4 + NaOH  NaC9H7O4 + H2O
*********, HASPI Medical Chemistry Lab ###
4
Name(s):
Period:
Date:
This is considered a neutralization reaction, because an acid (aspirin) and a base (NaOH) react to
form a salt and water.
If you look at the reaction you can see that this is balanced already with all coefficients of 1.
Your goal is to calculate the number of moles of NaOH needed to neutralize each type of acid. Then
you will determine how much of the 0.10M solution will be needed.
Calculate the molar mass of aspirin
Work:
Answer
Prediction: Baby Aspirin
Number of mg in one tablet
Number of grams in one tablet
Work
given
Answer
81mg
Work
given
Answer
325mg
Work
given
Answer
500.mg
Convert the grams into moles of aspirin
using the molar mass
Using your mole ratio, determine the
moles of NaOH required to neutralize this
sample of aspirin
If you have a 0.10M solution of NaOH
what is the volume of NaOH you will need
in L and mL? (M=moles/L)
Prediction: Regular Strength Aspirin
Number of mg in one tablet
Number of grams in one tablet
Convert the grams into moles of aspirin
using the molar mass
Using your mole ratio, determine the
moles of NaOH required to neutralize this
sample of aspirin
If you have a 0.10M solution of NaOH
what is the volume of NaOH you will need
in L and mL? (M=moles/L)
Prediction: Extra Strength Aspirin
Number of mg in one tablet
Number of grams in one tablet
Convert the grams into moles of aspirin
using the molar mass
Using your mole ratio, determine the
moles of NaOH required to neutralize this
sample of aspirin
If you have a 0.10M solution of NaOH
Aspirin Titration HASPI Medical Chemistry Lab
Draft 2/28/2014
5
Name(s):
Period:
Date:
what is the volume of NaOH you will need
in L and mL? (M=moles/L)
Aspirin Titration HASPI Medical Chemistry Lab
Draft 2/28/2014
6
Name(s):
Period:
Date:
Procedure/Directions
Your lab team will be giving tasks, or directions, to perform on the left. Record your questions,
observations, or required response to each task on the right.
Task
Response
1
Clean your buret. First rinse the buret with DI water, then rinse with
0.1M NaOH. Discard the water and NaOH used for rinsing. Fill your
buret with 0.100M NaOH, making sure to clear the tip of the buret.
2 Grind the children's aspirin into a fine powder using the mortar and
pestle. (If you have already titrated the children's aspiring move on to
the regular strength and extra-strength tablets)
3 Add 10mL of ethanol to your mortar and mix with your powdered aspirin
4 Use a pipette to transfer the ethanol-aspirin solution to your Erlenmeyer
flask
5 Add 25.0mL of DI water to the flask along with 2 drops of
phenolphthalein indicator. Swirl to mix.
6 Record the initial volume of NaOH in the data table.
7 Begin titrating. Add NaOH in 1mL increments while constantly swirling.
When the solution takes a longer time to turn clear, add NaOH drop by
drop, and swirl well between drops. STOP titrating when the color
change is permanent. The lighter the pink color the closer you are to the
end point.
8 Record the final volume of NaOH reached during your titration on your
data table
9 Clean out the Erlenmeyer flask and rinse with DI water.
Repeat steps 2-7 for regular strength and extra strength aspirin samples.
10 When all three titrations are complete, discard any remaining NaOH and
rinse your buret with DI water. Leave the buret clamped upside down
with the tip open to dry.
*Record data
*Record data
Data
Trial 1: Baby Aspirin
Initial Volume
NaOH
Final Volume
NaOH
Volume of
NaOH used
Trial 2: Regular Strength Aspirin
Initial Volume
NaOH
Final Volume
NaOH
Volume of
NaOH used
Trial 3: Extra strength Aspirin
Initial Volume
NaOH
Final Volume
NaOH
Volume of
NaOH used
Data Analysis - Calculations
Aspirin Titration HASPI Medical Chemistry Lab
Draft 2/28/2014
7
Name(s):
Period:
Date:
Results: Baby Aspirin
Number of mL required to reach endpoint
Number of moles NaOH titrated.
Remember it was 0.10M NaOH and
M=mol/L
Using your mole ratio, determine the
moles of aspirin neutralized by this
amount of NaOH
Calculate the grams of aspirin neutralized
in this trial of the experiment
Calculate the mg of aspirin neutralized in
this trial of the experiment.
Work
from experiment
Answer
Results: Regular Strength Aspirin
Number of mL required to reach endpoint
Number of moles NaOH titrated.
Remember it was 0.10M NaOH and
M=mol/L
Using your mole ratio, determine the
moles of aspirin neutralized by this
amount of NaOH
Calculate the grams of aspirin neutralized
in this trial of the experiment
Calculate the mg of aspirin neutralized in
this trial of the experiment.
Work
from experiment
Answer
Results: Extra Strength Aspirin
Number of mL required to reach endpoint
Number of moles NaOH titrated.
Remember it was 0.10M NaOH and
M=mol/L
Using your mole ratio, determine the
moles of aspirin neutralized by this
amount of NaOH
Calculate the grams of aspirin effectively
neutralized.
Calculate the mg of aspirin neutralized in
this trial of the experiment.
Work
from experiment
Answer
Aspirin Titration HASPI Medical Chemistry Lab
Draft 2/28/2014
8
Name(s):
Period:
Date:
Conclusions
1. Compare your predicted volumes of NaOH with your found volumes of NaOH using
the data table below.
%error = theoretical - actual x 100
theoretical
Baby Aspirin
Regular Strength
Aspirin
Extra Strength
Aspirin
Predicted
theoretical volume
of NaOH needed
Actual volume of
NaOH needed
Percent error
(show your work)
2. Acetyl salicylic acid (HC9H7O4) is a weak acid which means that hydrogen ions (H+)
partially dissociate in solution. Nevertheless, the hydrogen ions that did dissociate were
completely neutralized by the hydroxide ions (OH ). Describe how this can account for the
percent error above.
3. Aspirin is an acid. As an acid it gives of hydrogens when put into solution. Study the
reaction below and circle the hydrogen that is donated in this reaction. This is what we call
the acidic hydrogen.
4. Using the following data table, calculate the cost effectiveness of each type of
aspirin:
Baby Aspirin
Regular Strength
Extra Strength
Cost per bottle
$11.98
$9.47
$9.29
Pills per bottle
300.
200.
100.
Cost per pill
Grams Effective
*from your calculations
Cost per pill = cost effectiveness
grams effective
5.
Aspirin Titration HASPI Medical Chemistry Lab
Draft 2/28/2014
9
Name(s):
Period:
Date:
Connections & Applications
As per NGSS/CCSS incorporate extensions that allow teachers/students to choose outside activities
recommended by the standards.
Goal of having a minimum of 3 options for every lab activity, but more can be included. May include:
 Write a lab procedure for the study of aspirin over time












Critical thinking question(s) requiring research
Medical case study related and/or reinforcing concept
Investigating a phenomena
Designing an experiment
Developing and/or building a model
Creating a multimedia or visual display to convey a concept
Conduct a research project (correctly citing text is crucial)
Constructing an oral or written presentation/argument (correctly citing text is crucial)
Collecting data and construction graphical representations
Assess accuracy and credibility of a scientific publication
Mathematical computations
Resources and References
List of references
http://www.ijpsonline.com/article.asp?issn=0250474X;year=2010;volume=72;issue=5;spage=649;epage=651;aulast=Maheshwari
http://www.bostonglobe.com/lifestyle/health-wellness/2014/02/24/aspirin-may-cut-cancer-risk-but-itsbenefits-outweigh-possible-side-effects/dghiZ7q6Da17HyOIpI1KiI/story.html
http://health.howstuffworks.com/medicine/medication/aspirin2.htm
http://theunnecesarean.com/blog/2010/8/25/aspirin-in-early-pregnancy-may-preventpreeclampsia.html#sthash.3Whjm8fk.dpbs
Aspirin Titration HASPI Medical Chemistry Lab
Draft 2/28/2014
10