Chemistry Project Presentation

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Chemistry Project Presentation
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Objectives
To determine the best buy for different brands of
aspirin tablets
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Principle
In the experiment, the gram of acetylsalicylic
acid per 1 in different commercial brands of
aspirin tablets is carried out. Acetylsalicylic
acid can be hydrolyzed by using a known excess of
sodium hydroxide into the sodium salts of two
weak acids, ethanoic acid and 2-hydroxybenzoic
acid. The excess amount of sodium hydroxide is
then estimated by a back titration with standard
hydrochloric acid. The equation for the
hydrolysis reaction CH3CO2C6H4CO2H (s) 2NaOH
(aq) ?CH3CO2Na (aq) HOC6H4CO2Na (aq) H20(l)
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Chemicals used

• Two brands of 5 commercial aspirin tablets of the
  same type
• 1.00 M aqueous sodium hydroxide, 25 cm3 / 50 cm3
• Phenolphthalein indicator
• 0.100 M hydrochloric acid, about 40 cm3

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Sample used
A Bayer Aspirin B Disprin
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Procedure

• The mass of the 5 aspirin tablets were weighed
  accurately using electronic balance.
• The tablets became powder by using mortar and
  pestle they were then put into a beaker.
• A 25.00 cm3 pipette was used to transfer 25.00
  cm3 /50.00 cm3 of 1.00M sodium hydroxide into the
  beaker containing the 5 aspirin tablets. The
  beaker was then brought to the boil..
• The mixture was simmered gently for about 10-15
  minutes.
• The mixture of the beaker was then cooled down.

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5. The mixture was transferred into a 250.0 cm3
volumetric flask. Distilled water was added to
make the total volume up to the graduation
mark. 6. A 25.00 cm3 pipette was used to transfer
25.00 cm3 of the sample into a 250.0 cm3 conical
flask, and 3 drops of phenolphthalein indicator
were added. 7.The sample was titrated against
0.100M hydrochloric acid which held in a 50.00
cm3 burette until the colour of the mixture
changed from pink to colourless . 8.The titration
was repeated for 3 times. 9.The whole process was
repeated again with another sample.
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Observations
1.The solution changed from milky to pink when
phenolphthalein was added. 2.During titration,
the colour of the solution in conical flask
changed from pink to colourless.
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Results
Sample A Bayer Aspirin Mass of 5 tablets 2.99g
Average Volume of HCl added 101.30/5 20.26 cm3
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Sample B Disprin Mass of 5 tablets 2.37g
Average Volume of HCl added 36.8/6 6.13 cm3
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Calculation
CH3CO2C6H4CO2H (s) 2NaOH (aq) ? CH3CO2Na (aq)
HOC6H4CO2Na (aq) H20(l) HCl (aq) NaOH (aq) ?
NaCl (aq) H20 (l) Sample A Bayer
Aspirin Mass of 5 tablets 2.99g Mass of each
tablet 0.598g Average volume of HCl added
101.30/5 20.26 cm3 No. of moles of HCl added
in 25 cm3 solution 0.1 x (20.26/1000) 2.026
x 10-3 mol
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No. of moles of NaOH in 25 cm3 solution 2.026 x
10-3 mol No. of moles of NaOH remained in 250 cm3
solution 2.026 x 10-3 x (250/25) 2.026 x
10-2 mol No. of moles of NaOH reacted with
acetylsalicylic acid (50/1000) x 1- 2.026 x
10-2 mol 0.02974 mol No. of moles of
acetylsalicylic acid 0.5 x 0.02974 0.01487
mol
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Mass of acetylsalicylic acid 0.01487 x 180
2.6766g Mass of acetylsalicylic acid per tablet
2.6766 /5 0.53532g Gram of acetylsalicylic
acid / 1 0.53532 / (28/30) 0.574 gram of
acetylsalicylic acid /1
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Sample B Disprin Mass of 5 tablets
2.37g Mass of each tablet 0.474g Average volume
of HCl added 36.8/6 6.13 cm3 No. of moles
of HCl added in 25 cm3 solution 0.1 x
(6.13/1000) 6.13 x 10-4 mol No. of moles of
NaOH in 25 cm3 solution 6.13 x 10-4 mol
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No. of moles of NaOH remained in 250 cm3 solution
6.13 x 10-4 x (250/25) 6.13 x 10-3 mol No.
of moles of NaOH reacted with acetylsalicylic
acid (25/1000) x 1- 6.13 x 10-3 mol 0.01887
mol No. of moles of acetylsalicylic acid 0.5 x
0.01887 0.00943 mol
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Mass of acetylsalicylic acid 0.00943 x 180
1.698g Mass of acetylsalicylic acid per tablet
1.698 /5 0.3396g Gram of acetylsalicylic acid
/ 1 0.3396 / (13/24) 0.627 gram of
acetylsalicylic acid / 1
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Sources of Error

• The aspirin tablets did not dissolve completely.
• Error in human judgment on measuring solutions.
• Loss of solution during transference.
• Error in marking the end point.
• Systematic errors of the equipments.

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Precaution

• Safety goggles should be put on throughout the
  experiments.
• Didnt boil the mixture vigorously as it was
  explosive.
• It was better to put a glass rod in the beaker
  during boiling in order to reduce danger.
• Stirred continuously throughout the boiling in
  order to provide even heating on the mixture.

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Conclusion
Sample A (Bayer Aspirin) 0.574 gram of
acetylsalicylic acid / 1 Sample B (Disprin)
0.627 gram of acetylsalicylic acid / 1 From
the calculation, we find that the best buy for
the two brands of aspirin tablets is Sample B
(Disprin).
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Function of Aspirin
For quick and lasting relief of headache ,
toothache , feverish conditions and periodic
pains.
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How does Aspirin work???

• COX-2 is a enzyme made by our bodys cells whose
  job is to take chemicals floating around in our
  tissues and turn them into prostaglandins.
• Aspirin sticks to COX-2 and wont let it do its
  job. By taking aspirin, it decreases the pain
  signals getting through our nerves to our brain.

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How does Aspirin know how to get to where the
pain is??
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• When we take aspirin, it dissolves in our stomach
  or the small intestine, and our body absorbs it
  there. Then it goes into the bloodstreams and it
  goes through our entire body. Although it is
  everywhere, it only works where there are
  prostaglandins being made, which includes the
  area where it hurts.

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Side Effects
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• An aspirin may help the pain and swelling, but
  the wound may take longer to clot and stop
  bleeding. It is because acetylsalicylic acid
  decreases the ability of the platelets to clump
  together, so that clots cannot form as easily.
• Aspirin given to kids with flu, chickenpox, or
  other viral sicknesses may cause a potentially
  deadly problem called Reye syndrome.

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• Aspirin will upset the stomach. In the stomach,
  aspirin turns out another enzyme called COX-1,
  Aspirin keeps COX-1 from working and your stomach
  lining gets thin, allowing the digestive juice
  inside to irritate it. This is why aspirin and
  its relatives upset stomachs
• Aspirin also changes the way our kidneys make
  urine, can cause some people to have trouble
  breathing (rarely), and can be dangerous at very
  high doses.

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Who shouldn't take aspirin?
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• People who are allergic to acetylsalicylic acid,
  or have asthma, persisting or recurring stomach
  problems (such as heartburn, upset stomach or
  stomach pain), ulcers or bleeding problems should
  not take acetylsalicylic acid unless directed by
  a doctor.
• Do not use acetylsalicylic acid if you are taking
  a prescription drug for anticoagulation (thinning
  the blood), gout or arthritis unless directed by
  a doctor.

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Can I use acetylsalicylic acid
if Im diabetic? Diabetics should take
acetylsalicylic acid as analgesic only under a
doctor's supervision Combining acetylsalicylic
acid with oral anti-diabetes drugs can decrease
blood sugar levels more than expected.
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Can I take acetylsalicylic acid
if I am pregnant? Clinical studies have shown
that when used correctly acetylsalicylic acid is
safe for both mother and child. However, in the
last trimester of pregnancy, acetylsalicylic acid
should not be taken by pregnant women due to the
risk of a contraction-inhibiting effect.
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News about Aspirin
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Little aspirin a day stops big heart
attack!!! Anyone who has a heart attack should
take a daily low does of aspirin to prevent
another attack. Aspirin has a remarkable number
of effects including the ability to restrain
blood platelets from forming blood clots and
therefore keep them from contributing to heart
attacks. (The study was reported by Wilfred S.
Aronow in the May,1998 issue of The Journal of
American Geriatrics Society.)
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Better Choice
Ticlopidine better in preventing heart
diseases Ibuprofen , Naproxen , Motrin ,
Naprosyn also treat pain , swelling and fever
but they have less effect on platelets than
Aspirin
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The End