Formulate a hypothesis regarding the solubility of aspirin at different pH. The experiment A) Three teaspoons of water (approx. 15 ml) were added to one tablet said to contain 300 mg of aspirin. Fizzing was observed. Most of the tablet dissolved, but there were some solid particles. By heating the mug in a microwave for 10 second increments until the water came to the boil (approx. 3x), all of the solid particles dissolved. The solution was left to cool to room temperature and then placed in a fridge and NOTHING HAPPENED. Try this yourself if you can spare two aspirin tablets, your results might look different. • Questions to ask: 1. What might the fizzing bubbles be? 2. Can you give a chemical explanation? 3. Can you write a chemical reaction equation with aspirin reacting with something to give a gas and aspirin in another form?
Formulate a hypothesis regarding the solubility of aspirin at different pH.
The experiment
A) Three teaspoons of water (approx. 15 ml) were added to one tablet said to contain 300 mg of aspirin. Fizzing
was observed. Most of the tablet dissolved, but there were some solid particles. By heating the mug in a
microwave for 10 second increments until the water came to the boil (approx. 3x), all of the solid particles
dissolved. The solution was left to cool to room temperature and then placed in a fridge and NOTHING
HAPPENED. Try this yourself if you can spare two aspirin tablets, your results might look different.
• Questions to ask:
1. What might the fizzing bubbles be?
2. Can you give a chemical explanation?
3. Can you write a chemical reaction equation with aspirin reacting with something to give a gas and aspirin
in another form?
4. What might be the formulation (what the manufacturer mixes with aspirin in making the tablet) “trick”
for aspirin to improve solubility?
5. How does this compare with the published solubility of aspirin in water? – this is a physical property of
an organic compound.
B) Dissolve an aspirin tablet in vinegar (preferably, white, but any simple vinegar will do). Depending on the
strength of your tablet, you may need different amounts of vinegar – try one teaspoon at a time with heating in
between to increase solubility. Use the least amount of vinegar you can to dissolve the whole tablet. Cover the
mug with a saucer to prevent evaporation, slowly cooling to room temperature, then place in a fridge (or in a
container with ice cubes) and cooling further.
When the mug is cold, remove as many crystals that have formed as you can with a teaspoon and dry on paper
towel. You can perhaps even get more out with a paper towel and scrape them off using a teaspoon.
• Note and take photos your observations for each step of your experiment.
• Questions to ask:
6. What is vinegar and how does it influence the
7. Can you write reaction equations to explain the role of the vinegar on the component of the formulation
and the aspirin or aspirin salt? – (consider acid-base reactions)
Page 3
Ethics in Chemistry and Science
The skills you used in this experiment are used by drug addicts and clandestine chemists to get higher quantities
and concentrations of addictive drugs or starting materials to manufacture addictive drugs from medicines. As you
learn new skills in chemistry and science in general, you will be presented with opportunities to use them for good
or bad. What are your values? Where do you draw the line? The choice is yours!
To learn more visit: http://multiple.kcvs.ca/
C) Now that the aspirin has been purified as crystals from the tablet. Take your crystals and repeat the experiment
(A) using the minimum amount of water – one teaspoon at a time with heating.
• Note and take photos your observations for each step of your experiment.
• Compare your observations of C with those of A and B.
8. Can you explain any similarities and differences?
Reporting and Evaluation Rubric
Prepare a report of between 1000 and 1500 words with the following headings. You must submit a typed report as a
word document/pdf in the form that Turnitin can assess for plagiarism.
Title: Choose your own title.
Hypothesis: Formulate a hypothesis of what you believe to be going on in the experiment regarding changes in
solubility of aspirin and/or its pharmaceutical formulation that you can support with your observations.
Risk Analysis: Include your risk analysis (see above), steps taken to minimise risk, any proposed emergency
actions.
Method and Observations: This must be your method: Here you should note your source of aspirin, how many
spoons of solvent you used, how it was heated and for how long, etc. Include your observations with the report
of the method. You may crop photos and include the section of the photo that is relevant.
Discussion and Conclusions: This is where you discuss your observations with reference to the chemistry theory
using the questions posed above as a guide. You should type or draw the reaction equations, you may use
condensed structural formulae for organic compounds e.g. aspirin is acetyl salicylic acid CH3CO2C6H4CO2H. What
have you learnt about the pharmaceutical formulation of the aspirin you used and about the physical properties
of the compound. Compare your results or conclusions to literature (any information you find online) reference
the literature sources properly.
References: Use either the Harvard (Name in text, and references listed alphabetically) or Vancouver (Number in
text, and references listed in order of appearance) referencing style consistently. You may use any so
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